Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) serves not only as a key enzyme in glycolysis, but also as a multifunctional protein in other biological processes, especially in response to abiotic stresses in plants. Cytosolic GAPDH (GAPC) is a typical redox protein with selected catalytic cysteine, which undergoes reversible redox post-translational modifications (RPTMs) on its thiol group by reacting with hydrogen peroxide and nitric oxide related species. Moreover, the modified GAPC may interact with certain signal transmitters such as phosphatidic acid, phospholipase D, and osmotic stress-activated protein kinase. All these observations suggest that GAPC serve as a key mediator in redox signal transduction in plants. In this review, we provide an up-to-date insight into molecular mechanisms after H₂O₂- and NO-dependent oxidation of GAPC. We also discuss GAPC catalytic functions and potential functions as a modified protein by RPTMs.

Midvein is an important structure of the upright leaf of rice, and its normal development is essential to the formation of a common plant type of rice (Oryza sativa L.). To reveal the effect of midvein deficiency on photosynthesis-related characteristics, leaf microstructure, and vein characteristics, the photosynthetic features between the midvein-deficient mutant dl-14 and wild-type Huanghuazhan plants were analyzed. The results indicated that the midvein area of the dl-4 mutant lacked large intercellular space and instead it was filled with mesophyll cells. Moreover, the vein density of the dl-14 mutant was significantly higher than that in cv. Huanghuazhan. Chlorophyll (Chl) a, Chl b, and carotenoid content were markedly elevated in dl-14. In terms of photosynthetic characteristics, we observed that under high irradiance and high CO₂ concentration, the net photosynthetic rate of dl-14 plants was significantly higher than that of Huanghuazhan plants, but its water use efficiency was significantly lower. In addition, several major photosynthetic parameters, including characteristics of chlorophyll fluorescence (the efficiency of excitation capture of open PS II center, photochemical quenching, effective quantum yield of PS II photochemistry, and electron transfer rate) were significantly higher in dl-14 plants compared to Huanghuazhan plants, but the nonphotochemical quenching of dl-14 mutant was significantly lower than that of Huanghuazhan. These findings indicate that the dl-14 mutant has higher vein density, stronger photon conversion ability, and weaker radiation dissipation ability. This study can provide theoretical support for breeders to use the midvein-deficient mutant.

To reveal the regulation mechanism of terpenoid biosynthesis in the leaves of Eucalyptus camaldulensis, the content of volatiles in eucalyptus leaves and the transcriptome databases of young and mature leaves were analyzed. The results showed that E. camaldulensis contains 92 and 89 kinds of volatile substances in the young and mature leaves, respectively. Among them, the content of 1,8-cineole, β-pinene, and other substances was significantly different in young and mature leaves. A total of 99 802 unigenes were obtained from the transcriptome database of young and mature leaves of E. camaldulensis and 18 441 genes displayed obviously differential expressions during both developmental stages. There were 6 982 up-regulated unigenes and 11 461 down-regulated unigenes in the young leaf stage compared to the mature leaf stage. The key genes for terpenoid biosynthesis, including limonene synthase-10, limonene synthase-11, myrcene synthase-1, α- pinene synthase-2, and 1,8-cineole synthase-2, were selected for further analysis to explore the mechanism of gene regulation and genetic transformation. The expressions of key genes were validated by RT-qPCR, and their expressions were consistent with RNA-seq data. WRKY, MYB, NAC, and bHLH transcription factors (TFs) displayed important regulatory effects on the above key genes. Thus, a regulatory network model of terpenoid biosynthesis was constructed using target genes and TFs during leaf development in E. camaldulensis. These results provide theoretical evidence for understanding the terpenoid biosynthesis in plants and reference for terpenoids utilization by genetic engineering methods in E. camaldulensis.

Calcium is a critical component in a number of plant signal transduction pathways and the calcineurin B-like protein (CBL) family is a unique group of calcium sensors regulating a family of CBL-interacting protein kinases (CIPKs). In this study, two poplar CBL genes, PeCBL6 (GenBank acc. No. DQ907710) and PeCBL10 (GenBank acc. No. DQ899956), were characterized in transgenic Arabidopsis thaliana, particularly with regard to its role in abiotic stress resistance. Expression of the two CBL genes in poplar was induced by cold, drought, or high salinity, but not by abscisic acid (ABA) treatment. In Arabidopsis thaliana, PeCBL6 was found in the nucleus and PeCBL10 in the tonoplast. Transgenic Arabidopsis plants overexpressing PeCBL6 or PeCBL10 showed enhanced tolerance to high salinity, drought and low temperature. These results suggested that PeCBL6 and PeCBL10 may function as positive regulators of salt, drought and temperature responses.

Biochemical and transcriptional approaches can provide crucial evidence about the physiological changes which can occur in organic and conventional cultivated common orange [Citrus sinensis (L.) Osbeck]. This study aimed to investigate the change in physicochemical parameters, the concentrations of free amino acids and other N-containing compounds, and the expressions of key genes coding for enzymes linked to N assimilation in fruits of common orange cv. "Valencia Late". Two enzymes involved in different ways in N assimilation were considered: nitrate reductase (NR), catalyzing the conversion of nitrate into nitrite, and glutamate dehydrogenase (GDH), operating in the assimilation of ammonium (interacting with glutamate synthase), and in ammonium re-assimilation through glutamate deamination. Results showed that the different fertilizers did not affect the physicochemical characteristics of fruits but induced the different accumulation of free amino acids, with higher concentrations of proline and contemporarily lower concentrations of glutamate, in addition to upregulated the expression of GDH gene in fruits from organically managed tress. This study identified a possible adaptive response of common orange plants to organic or conventional fertilizers. The present work is intended as a first step to make the mechanisms underlying plant responses to N supply clearer by comparing organic and conventional cultivation. It also can support breeders to select the best citrus cultivars and agronomists to improve crop fertilization and production management.

Late embryogenesis abundant (LEA) proteins are important for promoting the growth and stress tolerance of plants. They are widely involved in plant growth regulation and responses to hormones and environmental factors. However, knowledge of the functions of the LEA gene in ginseng species remains limited. In this study, a Panax ginseng LEA gene (PgLEA) expression vector was constructed, and stable transgenic Arabidopsis lines were established. The PgLEA protein was classified in the LEA-2 subgroup. Reverse-transcription quantitative PCR analysis showed that the expression of PgLEA increased under 300 mM NaCl or 10 % (m/v) polyethylene glycol treatments. Under salt and osmotic stresses, overexpression of PgLEA in transgenic Arabidopsis plants improved germination rate, root length, and survival rate compared to wild-type plants. In response to drought or salt stress, transgenic plants increased proline accumulation, decreased malonaldehyde content and ion leakage. Furthermore, the transgenic plants exhibited significantly increased activity of superoxide dismutase, peroxidase, and catalase, and reduced accumulation of hydrogen peroxide and superoxide. Moreover, overexpression of PgLEA affected the expression of genes related to salt/drought stress. Taken together, PgLEA is a positive regulator of drought and salinity stress, and positively functioned in pleiotropic effects through regulating osmotic balance, reactive oxygen species scavenging and inducing transcription of stress-related genes. PgLEA may enable ginseng plants to adapt to adverse environments. The data presented herein imply that PgLEA may be useful for breeding new stress-tolerant ginseng cultivars.

Trehalose is a nonreducing disaccharide that is involved in the regulation of plant responses to a variety of environmental stresses. Trehalose 6-phosphate synthase (TPS) and trehalose 6-phosphate phosphatase (TPP) are two key enzymes in trehalose synthesis and they are widely distributed in higher plants. At present, TPS family genes have been systematically identified and analyzed in many plant species, but the TPP family genes have been rarely studied. In this study, ten TPS and six TPP genes in cannabis (Cannabis sativa L.) were identified at the genomic level. The phylogenetic tree of TPS and TPP family members in cannabis, Arabidopsis, and rice was constructed, and all the genes were divided into three subgroups: Class I, Class II, and Class III. The number of exons and motif types among Class I members was exactly the same, as were Class II members, but the gene structure and motif types of Class III members were slightly different. There were four pairs of CsTPSs and CsTPPs that had gene duplication, indicating that gene duplication events played an important role in the amplification of TPS and TPP families in cannabis. The results of expression analysis under abiotic stresses showed that 68.75 % of CsTPS and CsTPP genes were significantly induced by at least one abiotic stress. Among these genes, the expression of CsTPS1, CsTPS9, and CsTPPA was highest under at least one abiotic stress. These three genes may play a key role in abiotic stress responses. Most of the CsTPS and CsTPP genes that are closely located in the evolutionary tree have the same or similar functions. To our knowledge, this is the first paper that systematically reports the TPS and TPP gene families in cannabis.

Thioredoxins (Trx) are small multifunctional redox proteins that contain thioredoxin conserved domain and active site WCXXC. The Trx family has an important role in multiple processes, including electron transport, seed germination, redox regulation, biotic and abiotic stresses resistance, etc. Although Trx genes have been extensively characterized in some plants, they have not been reported in peanut until now. The identification of AhTrx genes provides potential candidate genes for studying their effects and regulatory mechanisms in peanut (Arachis hypogaea L.) growth and development, especially under aluminium (Al) stress. It is also helpful to further analyze the Al resistance pathway in plants. Seventy AhTrx genes were identified using a genome-wide search method and conservative domain analysis. Then the basic physicochemical properties, phylogenetic relationship, gene structure, chromosomal localization, and promoter prediction were studied by the bioinformatic methods. Furthermore, the expressions of AhTrx genes under different Al treatment times in two peanut cultivars were tested using a real-time quantitative polymerase chain reaction. Seventy AhTrx genes were identified and characterized. Phylogenetic tree analysis showed that all AhTrx members could be classified into 9 groups with different conserved domains. Motif 1 was found to exist in every sequence, with an active site. Furthermore, the gene structures showed that the AhTrx family was complicated and changeable during evolution. The chromosomal localization indicated that the distribution and density of the Trx family on 20 peanut chromosomes were uneven. Predictive promoter analysis indicated that AhTrx proteins might play a role in phytohormones synthesis and stress response. Finally, the expression patterns of the AhTrx genes showed that every gene was differently expressed under Al treatment in different peanut cultivars, some were obvious, others had no significant difference, some were at a high level, while others were at a low level. This study systematically identifies the Trx gene family in peanut, providing some candidates for further study on its effects and regulatory mechanism under Al stress in peanut.

Previous studies on microwave exposure on plants have revealed variations in sensitivity of plants to different microwave frequencies, exposure durations, and power intensities. However, the effects of different polarizations of microwaves on plants have not been studied. Therefore, we investigated the effect of horizontally and vertically polarized 2 GHz continuous microwaves on Myriophyllum aquaticum plants at 1.8 W m^-2 power density. The electric potential variation along the vascular tissues were investigated for 1.5 h and growth parameters, pigmentation, and H₂O₂ formation were studied during 48 h microwave exposure. Exposure to horizontally polarized microwaves, decreased standard deviation of electric potential variation and increased H₂O₂ content significantly. Vertically polarized microwaves increased the standard deviation of electric potential variation and photosynthetic pigments significantly. However, none of the polarizations altered growth parameters (shoot length, stem diameter, and internodal length). Thermographic images taken for 1 h continuous microwave exposure did not indicate alteration in the temperature of the plants for both vertical and horizontal polarities.

Proline, an amino acid, plays an important role in plants, and it is involved in stress resistance and development. Earlier, to study the proline role in maintaining stress resistance in plants, we obtained genetically modified transgenic lines of tobacco (Nicotiana tabacum L.) with reduced activity of proline dehydrogenase (PDH, the proline degradation gene) and increased content of proline. Transgenic tobacco plants demonstrated greater resistance to high concentrations of NaCl, drought, low temperatures, and heavy metals vs. control plants. The visual assessment showed that the leaf pubescence in transgenic plants varied noticeably. Here we apply automated analysis of the tobacco leaf folds to estimate quantitative characteristics of pubescence in genetically modified tobacco plants and the control SR1 line under non-stress conditions. Our results showed differences in the number of trichomes and their length between transgenic and control plants. The trichome number significantly increased in transgenic plants (from 1.5 to 3 times). The largest differences in the trichome numbers were observed for trichomes with lengths from 0 to 380 µm. When assessing the trichome length, the opposite was observed. In all three transgenic lines, the trichome length was significantly lower than that of the control SR1 line. The data obtained indicate the effect of proline as an important metabolome component affecting the plant phenotype. Our results demonstrate perspectives of tobacco transgenic lines as promising genetic models for studying the proline role in plant morphogenesis.

Drought and salinity, which can alter the water balance, disrupt the ionic equilibrium, and create reactive oxygen species (ROS), are capable of destroying plant tissues. In this study, transcriptomics, proteomics, and metabolomics have been used to elucidate various abiotic stress responses. In transcriptional signaling pathways, abscisic acid (ABA) is one of the plant phytohormones that regulate the stress response. On the other hand, several regulons and factors of transcription contributed in the reaction to osmotic stresses, as well as in ABA-dependent/independent signaling pathways. However, the findings display that intricate molecular reaction of plants under stress conditions may be controlled by complicated regulative networks of gene expression and signal transduction, as well as by the interaction between them. From the point of view of proteomics, protein modifications in response to stress can be considered as a molecular tool to improve the resistance of plants to environmental stresses. These studies have provided new information about the significance of several gene and protein networks involved in the response of plants to salinity and drought, and the induction of tolerance. Moreover, identifying the crucial pathways which are involved in salinity and drought resistance can open doors for the establishment of commercial-resistant crop cultivars, and might be very useful in the next-generation crop breeding strategies to produce plants with salinity and drought-resistant traits.

Cytokinins have been implicated in delaying leaf senescence. We previously generated transgenic cotton (Gossypium hirsutum L.) plants that harbor the Agrobacterium isopentenyl transferase gene (ipt) directed by a proteinase gene promoter. Here, we report that mRNAs were isolated from ipt cotton leaves and azygous leaves and were subsequently sequenced using Illumina Solexa technology. The sequence tags were searched against the TIGR database and the related gene expression profiles were compared resulting in the identification of 1 218 differentially expressed genes (DEGs): 719 up-regulated and 499 down-regulated. Analyzing the DEGs in the ipt cotton leaves showed that these genes belonged to four pathways: flavone biosynthesis, arginine and proline metabolism, glyoxylate and dicarboxylate metabolism, and RNA degradation. These pathways increased the activities of antioxidants, inhibited the effect of ethylene, and prevented degradation of macromolecules during senescence. The expression patterns of 17 genes were evaluated by real-time PCR and results were in agreement with the patterns of sequencing analysis. The identification of the DEGs may help us to understand a role of cytokinins in leaf senescence.

Paspalum fasciculatum Willd. ex Flüggé grows in mining soils which are Cd- and Pb-contaminated where it exhibits tolerance to Pb and the ability to extract Pb from these soils. To elucidate tolerance mechanisms to Pb-stress, liquid chromatography with tandem mass spectrometry (LC-MS/MS) was used to quantify changes in the accumulation of proteins in leaves. We identified 323 proteins involved in primary metabolism and response to biotic or abiotic stresses. Although proteins involved in the processes of photosynthesis and saccharide and energy metabolism presented the greatest amount of down-regulated proteins, the plant was able to maintain photosynthetic functions and obtain energy to sustain the vital balance. P. fasciculatum based their tolerance on increased antioxidant defenses, improving the protection and repair of proteins and transduction signals to coordinate physiological response to Pb-stress. Our results provide important information to understand the tolerance mechanisms in P. fasciculatum and could be important in future molecular studies on the resistance and accumulation of Pb in plants.

Long-term low temperatures restrict the regrowth of winter wheat (Triticum aestivum L.), thus decreasing agricultural output. Non-enzymatic expansins, which are related to plant growth, have been reported to respond to drought, salinity, and low-temperature stress. We obtained an expansin 3 gene, TaEXPA9. It is located in winter wheat cv. Dongnong with high cold hardiness. We analyzed the expression patterns of TaEXPA9-A/B/D in this cultivar and conducted a subcellular localization analysis of TaEXPA9-A/B/D in the onion epidermis. Transgenic Arabidopsis thaliana line with EXPA9-A/B/D overexpression was obtained to examine the effects of the orthologous genes of these expansins on plant growth and low-temperature stress resistance. The results showed that EXPA9-A/B/D expression significantly increased at 4 °C, it was higher in the roots than in shoots, and EXPA9-A/B/D was localized in the cell wall. The roots were well-developed in the transgenic A. thaliana, and the growth-related markers and setting rate were better than in the wild-type. Recovery was stronger in the transgenic plants after freezing stress. At low-temperature stress, the antioxidant enzyme activities and content of osmoregulatory substances in the TaEXPA9-A/B/D-overexpressing A. thaliana plants were significantly higher than in the wild-type plants, and the degree of membrane lipid peroxidation was lower. In summary, TaEXPA9 orthologous genes participate in the low-temperature stress response, and they might be of great importance in molecular breeding.

Sulphur (S) is incorporated into diverse primary and secondary metabolites that play important roles in proper growth and development of plants. In cereals, a fraction of the nitrogen (N) accumulated in developing grains is guaranteed by amino acid remobilization from vegetative tissues, a contribution that becomes critical when soil nutrients are deficient. Glutamine synthetase (GS) and amino acid transporters (AAT) are key components involved in N assimilation and recycling. The aim of the present study was to evaluate the effect of S availability on the expressions of HvGS and several selected HvAAT genes in barley plants and on the phloem exudation rate of amino acids. To this end, two independent experiments were designed to impose low S availability conditions to barley plants. Low S availability caused a decrease in the phloem exudation rate of amino acids as well as in the gene expression of all the HvGS genes and five of the six HvAAT genes analyzed. The strong correlation found between the phloem amino acid exudation rate and HvGS1-1, HvGS1-2, HvAAP7, and HvProT1 gene expression may indicate the participation of these genes in the regulation of amino acid remobilization through the phloem.

Sunflower broomrape (Orobanche cumana Wallr.) is considered a self-fertilizing species, but there is no indication as to whether it is strictly self-fertilized or that it presents some extent of cross-fertilization. The objective of this research was to measure the rate of cross-fertilization in O. cumana using an unpigmented recessive mutant as a visual marker. A pot and a field experiment in which single unpigmented plants were surrounded by a large number of pigmented plants were conducted. Occurrence of F₁ hybrids, readily distinguishable from unpigmented plants in the progenies of unpigmented plants provided a direct measurement of the cross-fertilization rate. Progenies of unpigmented plants contained 21.5 % of F₁ hybrids in the pot experiment and 28.8 % in the field experiment. The results revealed that O. cumana is a partially allogamous species, which has great relevance for understanding the genetic structure and dynamics of populations and, ultimately, race evolution in this parasitic plant.

In this study, the total and actual nitrate reductase (NR) activity, and NR activation state, in tomato seedlings (Solanum lycopersicum cvs. Kmicic and Faworyt) treated with okadaic acid (OA) was evaluated. Seedlings were grown in a half-strength Murashige and Skoog (MS) medium in a growth chamber at day/night temperatures of 22/20 °C, a photon flux density of 150 µmol m^-2 s^-1, and a 16-h photoperiod. After 10 days, plants were transferred into MS medium with 0 (control), 0.01, 0.05, 0.1, 0.5, 1.0 µM OA. It was found that the total and actual NR activity increased in Kmicic leaves treated with 0.1, 0.5, and 1.0 µM OA compared to control. However, the NR activation state did not change in both roots and leaves of OA-treated tomato seedlings.

High temperatures have become a major threat that seriously affects crop growth and yield. The present work aimed to investigate the acclimation process in adjusting plant responses to high root temperatures. Tomato (Solanum lycopersicum L., cv. Micro-Tom) during the flowering time was subjected to heat treatments (day/night temperatures at the root level of 40 or 45 °C for 4 d) while control plants were maintained at 25 °C, and the heat-stress treatment effects were analysed in the tomato leaves. The results showed a reduction in the content of chlorophylls a and b as well as chlorophyll a/b ratio at both high temperatures. Further, the increase in the amount of malondialdehyde as an indicator of lipid peroxidation was greater at 45 °C. The leaf content of hydrogen peroxide was induced in tomato plants subjected to 45 °C whereas it was markedly decreased in plants maintained at 40 °C as compared to control plants. Antioxidant enzymes showed higher activity in tomatoes treated at 45 °C compared to those treated at 40 °C. Moreover, the highest amount of antioxidants such as carotenoids and ascorbate in tomato plants were found at a temperature of 45 °C. Collectively, we provide evidence that physiological and biochemical components can be altered depending on the heat level, exposure time, and developmental stage. The interaction of root and shoot under high temperatures must be further characterized in terms of understanding the challenging climate changes.

The effects of nitric oxide (NO) and/or iron (Fe) supplied to Fe deficient plants have been investigated in peanut (Arachis hypogaea L.) grown in Hoagland nutrient solution with or without Fe. Two weeks after Fe deprivation, recovery was induced by addition of 250 μM sodium nitroprusside (SNP, a NO donor) and/or 50 μM Fe (Fe-EDTA) to the Fe deprived (-Fe) nutrient solution. Activities of antioxidant enzymes, leaf chlorophyll (Chl), and active Fe content decreased, whereas activities of H⁺-ATPase, ferric-chelate reductase (FCR), nitrate reductase, and nitric oxide synthase and NO production increased in Fe deficient plants, consequently an Fe chlorosis symptom appeared obviously. In contrast, these symptoms disappeared gradually after two weeks with NO and/or Fe supply, which caused an increases in leaf Chl and active Fe content, especially following by co-treatment with NO and Fe to values found in Fe sufficient plants. Increased activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and decreased accumulation of reactive oxygen species (H₂O₂, O₂^*- ) and malondialdehyde enhanced the ability of resistance to oxidative stress. Supplied NO alone had the obvious effect on increased NO production and on activity of H⁺-ATPase and FCR, whereas root length and root/shoot ratio were most effectively increased by Fe supplied alone. Co-treatment with NO and Fe did the best effects on recovery peanut chlorosis symptoms by significantly increased Chl and available Fe content and adjusted distribution of Fe and other mineral elements (Ca, Mg, and Zn) in both leaves and roots.

The plastidic thioredoxin F-type (TrxF) protein plays an important role in plant saccharide metabolism. In this study, a gene encoding the TrxF protein, named SlTrxF, was isolated from tomato. The coding region of SlTrxF was cloned into a binary vector under the control of 35S promoter and then transformed into Arabidopsis thaliana. The transgenic Arabidopsis plants exhibited increased starch accumulation compared to the wild-type (WT). Real-time quantitative PCR analysis showed that constitutive expression of SlTrxF up-regulated the expression of ADP-glucose pyrophosphorylase (AGPase) small subunit (AtAGPase-S1 and AtAGPase-S2), AGPase large subunit (AtAGPase-L1 and AtAGPase-L2) and soluble starch synthase (AtSSS I, AtSSS II, AtSSS III and AtSSS IV) genes involved in starch biosynthesis in the transgenic Arabidopsis plants. Meanwhile, enzymatic analyses showed that the major enzymes (AGPase and SSS) involved in the starch biosynthesis exhibited higher activities in the transgenic plants compared to WT. These results suggest that SlTrxF may improve starch content of Arabidopsis by regulating the expression of the related genes and increasing the activities of the major enzymes involved in starch biosynthesis.

We compared the defense against photoinhibitions and oxidative stress in transgenic rice expressing a modified Myxococcus xanthus protoporphyrinogen oxidase (MxProtox) gene and in wild-type (WT) rice. Although the MxProtox transgenic lines had higher content of protoporphyrin IX (Proto IX) than the untreated controls, they did not exhibit a drastic accumulation of Proto IX as in the WT after 2 d of 50 μM oxyfluorfen (OF) treatment. In the transgenic lines S4 and S11, the transcriptions of OsProtox and modified MxProtox genes were almost sustained in response to OF, although transcription of OsProtox was greatly down-regulated in the WT. The excess Proto IX in the WT plants treated with OF generated a severe stress mediated by singlet oxygen (¹O₂), leading to a prominent increases in electrolyte leakage and malondialdehyde production. This stress in the WT necessitated not only a substantial accumulation of zeaxanthin and antheraxanthin, but also strong increases in activities of superoxide dismutase, catalase, and peroxidase as well as transcriptions of CatalaseB, Ascorbate Peroxidase, and Heme Oxygenase2 genes. By contrast, the transgenic plants did not result in any noticeable increase in these parameters. Our results demonstrate that the transgenic rice expressing modified MxProtox efficiently prevented accumulation of photosensitizing Proto IX through sustaining higher transcriptions of porphyrin biosynthetic genes, thereby reducing the stress imposed by OF.

The tubular ray flower (turf) mutant of sunflower is characterized by a switch of ray flowers from zygomorphic to near-actinomorphic disc flowers. In sunflower, floral symmetry of ray and disc flowers is specified by the activity of members of a CYCLOIDEA (CYC) gene family. The turf mutant is generated by the insertion of a CACTA-like transposable element (TE), named Transposable element of turf1 (Tetu1), in the coding sequence of the HaCYC2c gene. The TEinsertion changes the reading frame of turf-HaCYC2c for the encoded protein and leads to a premature stop codon. Tetu1 is a non-autonomous version of a CACTA TEcarrying the minimum sequences necessary for transposition in the presence of autonomous elements in the sunflower genome. In the previous analysis, performed in more than 11 000 plants homozygous for the turf-HaCYC2c allele, the absence of chimerism and the segregation rate of derived-progenies from reverted phenotypes suggest that Tetu1 transpositions are restricted to a time shortly before and/or during meiosis. Here, we report the analysis of F₅ and F₆ progenies, derived from an F₄ progeny of the cross turf × Chrysanthemoides2, where plants with a chimeric inflorescence were detected. Tetu1 showed active excision in all progenies taken into consideration and named High Frequency of Tetu1 Transposition (HFTT). Within a total of 449 plants, Tetu1 excision generated a 13.81 % of non-chimeric revertants but also a 5.12 % of plants with somatic sectors of variable size in the outmost whorl of the inflorescence. These unexpected results suggest variations in tissue specificity and time of TEexcision. The excision of Tetu1 was confirmed by DNA molecular screening of non-chimeric and chimeric revertants and transcription analysis of the HaCYC2c gene. In HFTT progenies, sequence analyses excluded significant DNA changes with respect to the original Tetu1 transposon as well as to the adjacent 5'- and 3'-TE regions. Genetic and epigenetic regulatory mechanisms were proposed to explain the time and frequency of Tetu1 transposition in HFTT progenies.

Imidazolinone herbicides combined with imidazolinone resistant (IMI-R) crops provide a tool for solving the important problem of the occurrence of weeds during the early growth stages of sunflower. These herbicides inhibit the synthesis of branched chain amino acids by interrupting the key enzyme acetohydroxyacid synthase (AHAS). We studied the imazamox detoxification in an IMI-R sunflower hybrid together with plant growth and photosynthetic performance. Inhibition of photosynthesis and growth were observed as initial effects of imazamox application. A slight decrease in AHAS activity was also noticed. These effects disappeared within two weeks after application. A fast and well-functioning detoxification mechanism for the herbicide, of which the content decreased for about 90 % at 14 d after application, seems to be responsible for this. The activity of the xenobiotic detoxifying enzyme glutathione S-transferases (GSTs) significantly increased after imazamox application. Our results suggest that the metabolite glutathione serves as an auxiliary tool for imazamox detoxification through conjugation reactions realized by the GSTs, thereby taking part in the non-target mechanisms of resistance in IMI-R sunflower hybrids.

In a previous study, we have identified and characterized gene from wheat (Triticum aestivum L.) encoding F-box protein and named it TaFBA. In this paper, transgenic tobacco (Nicotiana tabacum L.) plants overexpressing TaFBA1 displayed accelerated growth early, but the rate slowed gradually at later stages of growth, and the mature transgenic plants were even shorter in stature and flowered later than did the wild type (WT). Treatment with gibberellin (GA) conferred an accelerated growth rate to the transgenic tobacco plants at later stages, similar to that of WT, whereas growth was inhibited more seriously in WT than in transgenic tobacco when plants were treated with a GA biosynthesis inhibitor. The content of GA in transgenic tobacco plants was higher at early developmental stages, but it was lower at later growth stages than in WT. Some GA biosynthesis genes were down regulated, which was accompanied with elevated expression of a GA catabolism gene. Thus, our results suggest that TaFBA1 is possibly involved in the regulation of plant growth and development, and that it may be related to the production, metabolism, and proper function of GA.

The utility of plant tissue culture for the mass propagation of trees is well known, but continuous in vitro multiplication of plant material may increase the possibility of somaclonal variation; therefore, it is essential to evaluate the genetic integrity of regenerants from species-specific in vitro protocols prior to mass production and implementation. The objectives of this study were: 1) to determine the effect of 2,4-dichlorophenoxyacetic acid (2,4-D) concentration over two cycles of secondary somatic embryogenesis in Magnolia dealbata; and 2) to verify the genetic stability of the regenerants obtained. The embryogenic response was not significantly affected by the concentration of 2,4-D but did vary across cycles of induction. The addition of 4.52 μM 2,4-D induced the highest total number of embryos (100.5), the mean number of somatic embryos (25.1) and somatic embryos per explant (80.6). In both 2,4-D concentration (2.26 or 4.52 μM), genetic integrity between the donor and the propagated clones was 0.90, and the low genetic instability (≤ 0.10 in both PGR treatments) might be due to effect of cyclic somatic embryogenesis or the different response of the explants at stress in in vitro culture conditions. However, it is necessary to examine more cell lines and somatic embryogenesis cycles.

The tonoplast and plasma membrane localized sodium (potassium)/proton antiporters have been shown to play an important role in plant resistance to salt stress. In this study, AtNHX1 and AtNHX3, two tonoplast Na⁺(K⁺)/H⁺ antiporter encoding genes from Arabidopsis thaliana, were expressed in poplar to investigate their biological functions in the resistance to abiotic stresses in woody plants. Transgenic poplar plants expressing either gene exhibited increased resistance to both salt and water-deficit stresses. Compared to the wild type (WT) plants, transgenic plants accumulated more sodium and potassium ions in the presence of 100 mM NaCl and showed reduced electrolyte leakage in the leaves under water stress. Furthermore, the proton-translocating and cation-dependent H⁺ (Na⁺/H⁺ or K⁺/H⁺) exchange activities in the tonoplast vesicles isolated from the leaves of transgenic plants were higher than in those isolated from WT plants. Therefore, constitutive expression of either AtNHX1 or AtNHX3 genetically modified the salt and water stress tolerance of transgenic poplar plants, providing a potential tool for engineering tree species with enhanced resistance to multiple abitotic stresses.

Alternative oxidase (AOX) transfers electrons from ubiquinone to oxygen in the respiratory chain of plant mitochondria. It is widely accepted that AOX functions as a mechanism decreasing the formation of reactive oxygen species (ROS) produced during respiratory electron transport. However, there are no experimental data to provide unambiguous proof of this hypothesis. We have studied growth characteristics, ROS content, and stress sensitivity in Arabidopsis transgenic lines with reduced or increased levels of AOX. We demonstrated that AOX-deficient plants grown in soil had an extended reproductive phase. Changes in AOX activity did not affect ROS content or stress sensitivity in the whole plants. However in the suspension culture, cells overexpressing AOX had significantly lower ROS content, whereas the AOX-deficient cells had higher ROS contents compared to the wild-type (WT) cells. Prooxidant treatment led to the increase in ROS content and to the reduction of viability more in the cells overexpressing AOX than in WT and AOX-deficient cells. Thus, we demonstrated that differences in the metabolism of whole plants and cultured cells might affect AOX functioning.

Plant cell lines represent useful models in plant cell biology. They allow simple analysis of the effects of various factors including modulated gene expression at cellular and subcellular levels. The tobacco BY-2 cell line is a favoured model due to its high proliferation rate, capability of effective synchronization, and accessibility to transformation. A relatively high uniformity of BY-2 cultures allows morphological phenotyping and assessment of growth parameters like mitotic index, viability, or cell density. Here we review already published and newly introduced optimized guidelines to carry out reliable, reproducible and efficient characterization of BY-2 cultures from suggestions of appropriate methods to acquire primary data, proper statistical treatment, and biological interpretation. The presented experimental data demonstrate the extent of natural variability and the effect of initial cell density on various cell culture features. Supportive equations allow to estimate some derived phenotypic parameters like cell cycle duration or fresh biomass of the culture and to determine the size of data sets for reliable documentation of a certain phenotypic change. The optimized protocols and accompanying discussion of weak points of different approaches should serve as practical guide for both beginners and experienced researchers working on BY-2 cells.

The root specificity and phosphate (Pi) deficiency responsiveness of high-affinity phosphate transporter (PHT1) genes point to their promoters as a sustainable system to drive Pi acquisition-related transgenes in plants. In this study, a 3-kb promoter of the AtPHT1;4 gene from Arabidopsis thaliana fused to the β-glucuronidase (GUS) reporter gene was biolistically introduced into wheat (Triticum aestivum L.) and functionally characterized in transgenic plants grown in hydroponics and in pots with soil under various Pi supply rates. From among 27 T₁ progeny derived from 250 T₀, four transgenic lines reached T₃, with two of them showing detectable GUS activity in the roots of T₄ plants. An unusually high number of transgene insertions characterized these transgenic lines, along with an irregular pattern of histochemical GUS staining and weak GUS activity. GUS expression driven by AtPHT1;4 was consistently higher under most assay conditions, as it was unaffected by 0 to 0.5 mM Pi in hydroponically grown plants, as well as by 16 to 20 mg(P) kg^-1(soil) in potted plants. Raising the soil P up to or above 40 mg kg^-1 significantly down-regulated the quantity of GUS transcripts. These results show that the responsiveness of the AtPHT1;4 promoter to Pi availability in transgenic wheat was restricted to soil-grown plants, which highlighted the relevance of the substrate and Pi supply rates in assessing molecular responses to Pi deficiency.

Dehydration responsive element binding factor (DREB) is believed to be a stress-tolerance enhancer in plants. In the present study, a cold-binding factor (CBF)/DREB homologous gene NnDREB1 (XP_010242642.1) was isolated from lotus roots using rapid amplification of cDNA ends (RACE) and reverse transcription (RT)-PCR methods. Analysis of the deduced amino acid sequence and phylogeny classified NnDREB1 into the A-1 group of the DREB1 subfamily. Expression profiling using a quantitative PCR method revealed that NnRDEB1 was significantly induced by NaCl, mannitol, and polyethylene glycol, but not by low temperature and abscisic acid. To evaluate function of NnRDEB1, Arabidopsis thaliana was transformed with the NnDREB1 gene in a binary vector construct. The transgenic plants exhibited higher resistance to drought compared with the wild-type plants in terms of survival rates, dry and fresh masses, and chlorophyll content. In addition, overexpression of NnDREB1 resulted in higher germination rates compared with the wild type plants on MS medium containing mannitol. The expressions of downstream target stressrelated genes, including cold-regulated15B (COR15B), rare cold inducible 2B (RCI2B) and repeat domain 26 (RD26), were activated in the transgenic plants. Taken together, the results suggest that NnDREB1 might be an important protein in lotus root drought tolerance.