Sulfur dioxide is a widespread air pollutant and it also acts as a signaling molecule in various processes in mammals. However, the role of SO₂ in programmed cell death (PCD) in plants is unclear. Here we studied the role of SO₂ in gibberellin (GA)-treated wheat aleurone layers. The results showed that 100 μM SO₂ donor (NaHSO₃/Na₂SO₃) could effectively delay PCD and inhibit the coalescence of small protein storage vacuoles (PSVs) in aleurone cells treated with GA. Also, SO₂ could reduce the accumulation of hydrogen peroxide and superoxide anion in GA-treated aleurone layers. In this process, SO₂ could sustain higher activities of catalase, guaiacol peroxidase, ascorbate peroxidase, and superoxide dismutase and lower activities of lipoxygenase and polyphenol oxidase by comparing with GA alone. In addition, an induction of endogenous H₂S and NO was observed in SO₂-treated aleurone layers. The application of NO scavenger cPTIO could accelerate PCD in SO₂ or H₂S treated aleurone cells, suggesting that NO alleviated PCD by acting downstream of SO₂ and H₂S. In conclusion, these results imply that SO₂ could delay PCD in GA-treated wheat aleurone layers by enhancing cellular antioxidative capacity and H₂S/NO signals act downstream of SO₂.

Tomato (Solanum lycopersicum) plants have four fructokinase genes, SlFRK1-4. The SlFRK4 is expressed only in pollen whereas the other three are expressed in all plant parts. While SlFRK2 and SlFRK3 are involved in vascular tissue development and affects the shape, size, and cell-wall width of xylem vessels and xylem fibers, the role of SlFRK1 has not been studied previously. The current work investigates the expression of SlFRK1 using transgenic tomato plants expressing the β-glucuronidase reporter gene under the SlFRK1 promoter, as well as the role of SlFRK1 using transgenic plants with antisense suppression of SlFRK1. The SlFRK1 promoter is expressed primarily in vascular tissues and specific suppression of SlFRK1 reduces water transport in stems, but has no other anatomical or phenotypic effects. Combined suppression of SlFRK1 and SlFRK2 severely inhibited plant growth and an anatomical analysis revealed a reduction in secondary xylem area and distorted phloem fibers characterized by thin cell walls and reduced lignification. The results suggest that SlFRK1 is involved in vascular tissue development and hydraulic conductivity in tomato plants and that SlFRK1 is important for normal phloem fiber development, together with SlFRK2.

DNA methylation is one of the epigenetic mechanisms regulating gene expression in plants in response to environmental conditions. In this study, analysis of methylation patterns was carried out in order to assess the effect of water stress in two contrasting wheat genotypes using methylation-sensitive amplified polymorphism (MSAP). The results revealed that demethylation was higher in drought-tolerant genotype (C306) as compared to drought-sensitive genotype (HUW468) after experiencing drought stress. Comparisons of different MSAP patterns showed a high percentage of polymorphic bands between tolerant and susceptible wheat genotypes (from 74.79 % at anthesis to 88.89 % at tillering). Furthermore, differential DNA methylation in roots and leaves also revealed tissue-specific methylation of genomic DNA. Interestingly, 54 developmental stage-specific bands and 23 bands that were found contrasting between these two wheat genotypes were detected. Furthermore, a few sites with stable DNA methylation differences were identified between drought-tolerant and drought-sensitive cultivars, thus providing genotype-specific epigenetic markers. These results not only provide data on differences in DNA methylation changes but also contribute to dissection of molecular mechanisms of drought response and tolerance in wheat.

Uridine diphosphate glucose dehydrogenase (UGDH) plays an important role in biosynthesis of hemicellulose by catalyzing oxidation of UDP-glucose (UDP-Glc) to UDP-glucuronate (UDP-GlcA), a key sugar nucleotide involved in biosynthesis of the plant cell wall. In this study, a UGDH ortholog referred to as LgUGDH was isolated from Larix gmelinii using PCR and rapid amplification of cDNA ends techniques. Real-time PCR shows that the LgUGDH gene was expressed primarily in larch stems in addition to its roots and leaves, and Southern blot analysis indicates that UGDH is encoded by two paralogous genes in L. gmelinii. Overexpression of LgUGDH increased the content of soluble sugars and hemicelluloses and enhanced vegetative growth and cold tolerance in transgenic Arabidopsis thaliana. These results reveal that L. gmelinii UGDH participates in sucrose/polysaccharide metabolism and cell wall biosynthesis and may be a good candidate gene for enhancing plant growth, cold tolerance, and hemicellulose content.

We studied changes in physiological parameters of whole leaves and in antioxidant protection of chloroplasts during ageing and senescence of tobacco (Nicotiana tabacum L. cv. Samsun NN) leaves with enhanced cytokinin oxidase/dehydrogenase activity (CKX) or without it (WT). Old leaves of CKX plants maintained higher pigment content and photosystem 2 activity compared to WT leaves of the same age. Chloroplasts of old CKX plants showed better antioxidant capacity represented by higher superoxide dismutase, dehydroascorbate reductase and glutathione reductase activities.

In Arabidopsis, EXPORTIN1A (HIT2/XPO1A) and EXPORTIN1B (XPO1B) mediate the translocation of nuclear export sequence (NES)-bearing proteins from nucleus to cytoplasm. However, a mutation in HIT2/XPO1A but not in XPO1B induces sensitivity to high irradiance (HI). Arabidopsis thaliana heat stress elements A4a and A5 (AtHsfA4a and AtHsfA5) are involved in plant responses to HI and possess NESs; therefore, their nucleo-cytoplasmic partitioning was analyzed. In wild-type and xpo1b mutant cells, AtHsfA4a normally remained in the cytoplasm but became concentrated in the nucleus following exposure to HI, whereas AtHsfA5 was constitutively distributed in both cytoplasm and nucleus. However, in hit2/xpo1a mutant, AtHsfA4a and AtHsfA5 were always confined to the nucleus, regardless of the irradiance. Although AtHsfA4a can enhance the ability of plants to scavenge H₂O₂, and AtHsfA5 is a repressor of AtHsfA4a, athsfa5 but not athsfa4a mutant plants exhibited HI sensitivity. Additionally, athsfa4a plants expressing AtHsfA4aΔNES were sensitive to HI, but athsfa5 plants expressing AtHsfA5ΔNES were not. Meanwhile, hit2/athsfa4a double mutant was more tolerant to HI than hit2. These results indicate that both AtHsfA4a and AtHsfA5 were HIT2/XPO1A-specific substrates. Long-term accumulation of AtHsfA4a contributed to the hit2 HI-sensitive phenotype independent of the scavenging ability of H₂O₂, and the presence of AtHsfA5 could mitigate this adverse effect.

Phosphites (Phis), inorganic salts of phosphorous acid, have shown to be effective in protection of plants against biotic stress. Recently, we have described that potassium phosphite (KPhi) induces tolerance to UV-B radiation in potato. To counteract the harmful effect of UV radiation, plants accumulate UV-screening compounds, such as flavonoids, sinapate ester, and lignin. In previous work, we have shown an increase in guaiacol peroxidase (POD) activity in plants pretreated with KPhi and further exposed to UV-B radiation. In order to continue with this study, the expression of different enzymes and components involved in cell wall reinforcement were analyzed. An isoform of POD induced by KPhi was analyzed by isoelectric focusing and further identified as suberization-associated anionic peroxidase (POPA) by mass spectrometry. In addition, other enzymes participating in lignin biosynthesis, like caffeoyl-CoA O-methyltransferase (CCoAOMT), determined by accumulation of transcripts, and laccase activity, visualized in zymogrames, were increased by KPhi treatment previous to UV-B exposure. Further, the accumulations of extensin (EXT) transcripts and of conjugated polyamines (PAs) were increased by KPhi treatment previous to UV-B exposure. All these results suggest cell wall reinforcement in leaves due to KPhi pretreatment followed by UV-B exposure.

Root hairs play important roles in plant nutrient and water acquisition. To better understand the genetic mechanism controlling root hair development in rice (Oryza sativa L.), a rice mutant with root hair defects was isolated and characterized. Cryo-scanning electron microscope (SEM) showed that the density and length of root hairs in the mutant were significantly reduced compared to wild type (WT). Map-based cloning and complementation test revealed that the mutation occurred in a NADPH oxidase gene OsNOX3 (LOC_Os01g61880). The OsNOX3 displays high sequence similarity with the previously characterized NOX genes RTH5 in maize and RHD2 in Arabidopsis, which play critical roles in root hair development. Expression pattern analysis indicated that OsNOX3 is expressed in various tissues throughout the plant with high expression in roots and root hairs. Subcellular localization analysis confirmed that OsNOX3 is located on the plasma membrane. Staining assays showed that the content of superoxide and hydrogen peroxide are significantly reduced in root hair tips of Osnox3 when compared to WT. Our results showed critical roles of OsNOX3 in regulating both root hair initiation and elongation in rice, which is similar to RTH5 but different from RHD2, confirming the difference of genetic mechanisms regulating root hair morphogenesis in monocot and dicot plants.

Gibberellins (GAs) are a large family of tetracyclic diterpenoids, controlling important aspects of growth and development throughout the plant life cycle. To explore the possibility that gibberellin A₃ (GA₃) signalling induces epigenetic alteration(s), we carried out a field experiment study using Nicotiana tabacum as a model system. The GA₃ application on leaves resulted in increased plant-height, foliage density, leaf cell area, and trichome density. The plants exposed to GA₃ also exhibited: 1) increased chromatin de-condensation, 2) reduced global DNA methylation, 3) reduced DNA methyltransferases (NtDNMTs) activities accompanied by decreased amounts of NtMET1 and NtCMT3 transcripts, and 4) partial restoration of phenotype and expression of epigenetically silenced reporter transgene. Based on these observations, we propose that GA₃ application induces complex epigenetic re-programming, which may lead to distinct developmental phenotypes. These results could provide an important insight for future studies on epigenetic mechanism(s) in other important crops.

Heat causes stress in blueberry; therefore, the present study aimed to investigate whether exogenous ferulic acid (FA) might protect plants against heat stress and to analyze possible mechanisms underlying such protection. Blueberry (Vaccinium corymbosum) seedlings were pretreated with 0.6 mM FA for 1 d and then kept at normal (25/20 °C) or elevated (39/30 °C) temperatures for 3 d. One day of FA pretreatment increased transcriptions of genes encoding iron superoxide dismutase, cytoplasmic copper/zinc superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase and elevated content of proline and soluble sugars in leaves. When the FA-pretreated blueberries were exposed to heat, transcriptions of these genes and content of proline and soluble sugars were higher than after heat treatment alone. Under heat, FA pretreatment also enhanced transcriptions of genes encoding chloroplast copper/zinc superoxide dismutase, catalase, glutathione peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase. This corresponds with increased activities of superoxide dismutase and glutathione peroxidase and is consistent with elevated content of ascorbate and glutathione in the FA-pretreated and heat-stressed blueberries. Compared with heat treatment alone, the combination of FA pretreatment and heat enhanced content of endogenous FA, decreased production of superoxide anion, and content of hydrogen peroxide and malondialdehyde, and also increased relative water content and osmotic potential in the leaves. Thus, pretreatment with FA mitigated the heat stress in the blueberries by elevating endogenous FA content, reducing accumulation of reactive oxygen species, and increasing proline and soluble sugar content.

This review reports the physiological and metabolic changes in plants during development under elevated atmospheric carbon dioxide concentration and/or limited-nitrogen supply in order to establish their effects on leaf senescence induction. Elevated CO₂ concentration and nitrogen supply modify gene expression, protein content and composition, various aspects of photosynthesis, sugar metabolism, nitrogen metabolism, and redox state in plants. Elevated CO₂ usually causes sugar accumulation and decreased nitrogen content in plant leaves, leading to imbalanced C/N ratio in mature leaves, which is one of the main factors behind premature senescence in leaves. Elevated CO₂ and low nitrogen decrease activities of some antioxidant enzymes and thus increase H₂O₂ production. These changes lead to oxidative stress that results in the degradation of photosynthetic pigments and eventually induce senescence. However, this accelerated leaf senescence under conditions of elevated CO₂ and limited nitrogen can mobilize nutrients to growing organs and thus ensure their functionality.

Senescence is the last developmental stage in plants during which recycling of nutrients takes place from senescing organs to newly formed organs such as young leaves and developing seeds. In the present work, senescence induced alterations in mineral ions, chlorophylls, carotenoids, betacyanin, betaxanthin, proteins, amino acids, sugars, starch, and polyphenols were monitored in shoots of an extreme halophyte Salicornia brachiata. A sharp decline in the content of chlorophylls, carotenoids, and proteins in the shoot was noticed at middle and late stages of senescence in comparison with early stage. However, the content of betacyanin, betaxanthin, total soluble sugars, reducing sugars, and starch increased significantly in senescing shoots. The total free amino acid content decreased gradually with the progress of senescence. The content of major minerals did not change significantly with the progress of senescence, whereas marked changes in content of minor minerals were observed. From this study, it was concluded that the sugars and starch accumulating in senescing shoots might be transported into developing seeds to serve as storage nutrients. The accumulation of betacyanin and betaxanthin in senescing shoots suggests that these pigments may act as scavengers of reactive oxygen species during senescence. This study provides comprehensive information on the variations in the utilization of mineral nutrients and organic metabolites with progressing senescence in the halophyte S. brachiata.

Pathogenesis-related (PR) proteins play key roles in plant disease resistance. Here, we isolated and characterized pathogenesis-related PR2 gene encoding β-1,3-glucanase from Brassica juncea and named it BjPR2 (GenBank accession number DQ359125). The amino acid sequence of BjPR2 showed ~99 % similarity with β-1,3-glucanase of Brassica rapa, B. napus, and B. oleracea. BjPR2 transcription was rapidly increased after Alternaria brassicae infection, salicylic acid application, and wounding, but the induction was delayed in response to jasmonic acid. To investigate the transcriptional regulation of BjPR2 gene, its promoter was isolated. In silico analysis of BjPR2 promoter showed cis-regulatory elements upstream of TATA and CAAT boxes responsive to defense, hormones, wounding, and plant developmental stage. Homozygous Arabidopsis thaliana lines were developed with plasmid construct having β-glucuronidase (GUS) reporter gene driven by BjPR2 promoter. The analysis of GUS protein in Arabidopsis lines showed that BjPR2 promoter drived distinct pattern of pathogen inducible expression after fungal infection (Alternaria brassicae, Erysiphe orontii), phytohormones, and wounding. It also showed age dependent and organ specific expressions. BjPR2 promoter drove strong GUS activity in Arabidopsis seedlings and showed organ specific expression at the later growth stages (lateral organ junctions, leaf serrate, base of siliques, and receptacle). Due to stress-inducible and tissue specific nature, the BjPR2 promoter can serve as a potential candidate in genetic engineering.

Zinc is the most widespread deficient micronutrient in the tea growing soils of India which affects growth of the plants. In order to investigate the structural, physiological, and biochemical changes under Zn stress (i.e. both deficient and excess supply) of tea [Camellia sinensis (L.) O. Kuntze cv. T-78] plants, we treated young plants with ZnSO₄ at 0 (deficiency), 0.3, 3 (optimum), and 30 μM (toxic) concentrations for 8 weeks. Zn deficiency and excess resulted in considerable decrease in shoot and root fresh and dry masses, and transmission electron microscopy (TEM) revealed disorganization of some cellular organelles. Further, Zn-stress decreased net photosynthetic rate (P_N), transpiration rate (E), stomatal conductance (g_s), and content of chlorophylls a and b. On the other hand, content of superoxide anion, malondialdehyde, hydrogen peroxide, and phenols, and electrolyte leakage were elevated in stressed plants. The activities of ascorbate peroxidase, catalase, superoxide dismutase, and peroxidase as well as expression of respective genes were up-regulated under Zn-stress. Nevertheless, antioxidant system as a whole did not afford sufficient protection against oxidative damage.

Auxins are one of the main regulators of in vitro plant growth and development. However, the mechanisms, by which auxins, such as 1-naphthaleneacetic acid (NAA), affect in vitro root and leaf anatomy and photosystem function, remain unclear. Accordingly, the aim of the present study was to analyze the effect of different NAA concentrations on the anatomy and photosynthetic performance of in vitro-propagated Aechmea blanchetiana and to determine whether such a treatment affects micropropagated plants after acclimatization. In vitro-established A. blanchetiana plants were transferred to culture media that contained 0, 2, 4, or 6 μM NAA, and after 50 d, they were transplanted into plastic seedling trays with a commercial substrate and cultivated for 60 d in a greenhouse. The plants were evaluated after a 50-d in vitro NAA exposure (growth traits, chlorophyll α fluorescence, and root and leaf anatomy) and after 60 d of acclimatization in the greenhouse (root and leaf growth). Changes induced by NAA in root anatomy might improve uptake of minerals and sugars from the medium, thereby increasing the in vitro growth. In the leaves, the lowest chlorenchyma thickness and sclerenchyma area were observed in plants grown without NAA, and NAA exposure also improved photosystem II activity. The highest ex vitro growth rate was observed for plants that were propagated with 4 μM NAA. Therefore, the use of NAA during in vitro propagation can improve the anatomical and physiological quality of A. blanchetiana plants, as well as to improve ex vitro transfer.

Ion transporters play an important role in ion homeostasis and control ion flow from its intrusion to exclusion in the entire plant system. Abiotic stress tolerance in plants depends immensely on the activity of these transporters. The transporter proteins are transcriptionally regulated by cis-elements present in their upstream region for specific activity. The presence of different cis-elements facilitates cross-talk between different signal transduction pathways. Depending on the cis-elements, a specific stress signalling pathway is activated, eliciting a physiological change towards maintaining ion homeostasis to alleviate stress. Beta-glucuronidase localization studies using various promoter regions indicated their expression specificity in organs/tissues. This review gives an overview about promoter activity of different transporters and its involvement under salinity stress.

This work studied the six β-galactosidases (BGALs) of the subfamily a1 of Arabidopsis, that have been proposed to play important roles in the cell wall remodelling during plant development, although their precise functions are still unknown. Knockout mutants bgal1, bgal2, bgal3, bgal4, bgal5, and bgal12 of Arabidopsis and their wild type (WT) plants were analysed to determine their morphology and composition of their cell walls. The gas chromatography and the Fourier transform infrared spectroscopy revealed differences between the mutants and their WT such as in the proportions of glucose, galactose, or xylose in bgal2 and bgal4 and in cell walls polysaccharides in bgal1, bgal3, and bgal5. However, these slight changes did not result in morphological variations during plant development. None of the mutant seedlings displayed a clear reduction in β(1,4)-galactan content, analysed by immunolocalization. The absence of significant phenotypic changes in the β-galactosidase subfamily a1 mutants could indicate possible β-galactosidases functional redundancy. Future studies will focus on the construction of multiple mutants that help to establish the precise function of each member of the β-galactosidase subfamily a1.

Root cortical aerenchyma (RCA) is suggested to reduce metabolic cost for root growth, but it might lower water uptake by plants. The objective of this work was to evaluate the effects of drought and phosphorus on the RCA development along the root axis and to elucidate its role in water stress tolerance of two maize genotypes. Plants of drought-tolerant DKB390 and drought-sensitive BRS1010 genotypes were grown in Vermiculite at field capacity of 100, 75, 50, and 25 % and supplied with 0.1, 0.4, and 0.8 mM phosphorus. Growth parameters, RCA, and plant P content were evaluated for all plants. Higher RCA development was observed in DKB390 than in BRS1010. Drought reduced the percentage of RCA in the root-hair zone of both genotypes but increased its development in the root maturation zone. Phosphorus limitation enhanced RCA development only in the DKB390. Under drought stress, DKB390 showed resilient growth whereas growth was inhibited in BRS1010. Higher root P content was related to its higher supply. Therefore, RCA formation was induced either by drought or by phosphorus limitation, while no interaction was evident. The RCA development varied along the root axis in order to balance water and phosphorus uptake and the drought response was genotype dependent.

Salinity is one of the major abiotic constraints to agriculture. The physiological and molecular mechanisms of salt tolerance have been studied in plants for many years. The regulation of osmosis and ion homeostasis is crucial. A lot of important components involved in plant responses to salt stress have been identified. Among them, ion transporters and channels take an essential role in ion homeostasis, mainly for Na⁺, Cl^-, and K⁺. Until now, many cation antiporters important for salt tolerance in plants have been characterized. Among them, the monovalent cation/proton antiporters (CPA) family is one of the most important families, including sodium proton exchangers (NHXs), K⁺-efflux antiporters (KEAs), and cation/H⁺ exchangers (CHXs). Here, the current knowledge of the plant CPA family in responses to salt stress was reviewed. The regulation mechanisms were also included and discussed.

Mapping of quantitative trait genes (QTGs) associated with drought related traits is essential for improving drought tolerance in crop species. In silico identification of candidate genes relies on annotation of critical QTGs to a variety of web resource-based datasets. The barley reference sequence was employed to map QTGs significantly associated with the proline accumulation and osmotic potential. Annotation of the critical QTGs contigs to the NCBI protein database identified 72 gene orthologs located on chromosomes 1H, 2H, and 7H, from which seven genes were identified as candidates. Expression analysis of all seven candidate genes revealed differential expression pattern between plants grown under well-watered conditions and drought-stress. The results represent a successful and highly powerful implementation of genome-wide scanning approach based on in silico mapping of QTGs to identify gene clusters having a common transcript pattern with similar function.

Elucidation of mechanisms underlying plant tolerance to cadmium, a widespread toxic soil pollutant, and accumulation of Cd in plants are urgent tasks. For this purposes, the pea (Pisum sativum L.) mutant SGECd^t (obtained by treatment of the laboratory pea line SGE with ethylmethane sulfonate) was reciprocally grafted with the parental line SGE, and four scion/rootstock combinations were obtained: SGE/SGE, SGECd^t/SGECd^t, SGE/SGECd^t, and SGECd^t/SGE. They were grown in hydroponics in the presence of 1 μM CdCl₂ for 30 d. The SGE and SGECd^t scions on the SGECd^t rootstock had a higher root and shoot biomass and an elevated root and shoot Cd content compared with the grafts having SGE rootstock. Only the grafts with the SGE rootstock showed chlorosis and roots demonstrating symptoms of Cd toxicity. The content of nutrient elements in roots (Fe, K, Mg, Mn, Na, P, and Zn) was higher in the grafts having the SGECd^t rootstock, and three elements, namely Ca, Fe, and Mn, were efficiently transported by the SGECd^t root to the shoot of these grafts. The content of other measured elements (K, Mg, Na, P, and Zn) was similar in the root and shoot in all the grafts. Then, the non-grafted plants were grown in the presence of Cd and subjected to deficit or excess concentrations of Ca, Fe, or Mn. Exclusion of these elements from the nutrient solution retained or increased differences between SGE and SGECd^t in growth response to Cd toxicity, whereas excess of Ca, Fe, or Mn decreased or eliminated such differences. The obtained results assign a principal role of roots to realizing the increased Cd-tolerance and Cdaccumulation in the SGECd^t mutant. Efficient translocation of Ca, Fe, and Mn from roots to shoots appeared to counteract Cd toxicity, although Cd was actively taken up by roots and accumulated in shoots.

There is evidence that the plasma membrane (PM) permeability alterations might be involved in plant salt tolerance. This review presents several lines of evidence demonstrating that PM permeability is correlated with salt tolerance in plants. PM injury and hence changes in permeability in salt sensitive plants is brought about by ionic effects as well as oxidative stress induced by salt imposition. It is documented that salinity enhances lipid peroxidation as well as protein oxidative damage, which in turn induces permeability impairment. PM protection, and thus retained permeability, in tolerant plants under salt imposition could be achieved through increasing antioxidative systems and thereby reducing lipid peroxidation and protein oxidative damage of PM. It appears that specific membrane proteins and/or lipids are constitutive or induced under salinity, which may contribute to maintenance of membrane structure and function in salt tolerant plant species. Furthermore, protecting agents (e.g., glycinebetaine, proline, polyamines, trehalose, sorbitol, mannitol) accumulated in salt tolerant species/cultivars may also contribute to PM stabilization and protection under salinity. Based on the presented evidence that PM permeability correlates with plant salt tolerance, we suggest that PM permeability is an easy and useful parameter for selection of genotypes of agriculture crops adapted to salt stress.

Structural alterations of chromosomes are often found in wheat-rye hybrids. In the majority of cases modifications are observed for rye chromosomes, yet chromosome aberration cases are described for wheat, including the progeny of Triticum aestivum disomic and monosomic addition lines. Since wheat-rye substitution and translocation lines are the source of rye chromatin in wheat breeding programs, the information on possible chromosome changes in the genomes of introgressive forms is important. Chromosome behavior in F₁ meiosis and chromosomal composition of F₂ karyotypes for double monosomics 1Rv-1A were studied by applying C-banding, genomic in situ hybridisation (GISH) using rye genomic DNA, and sequential in situ hybridization using repetitive sequences pAs1, pSc119.2 and centromere specific pAet-06 as probes. The double monosomics 1Rv-1A were obtained by crossing of disomic substitution line with chromosome 1A replaced by Secale cereale 1Rv in the bread wheat Saratovskaya 29 (S29) background with S29. The results indicated a high frequency of bipolar chromosome 1Rv orientation, as compared to 1A, at metaphase I (MI) (58.6 and 34.7 % of meiocytes, respectively), and, at anaphase I (AI), chromatid segregation of 1Rv compared to 1A (70.53 and 32.14 % of meiocytes, respectively). In few cases desynapsis of wheat homologues was observed, at AI, the chromosomes randomly distributed between the poles or underwent chromatid segregation. At AI, the two wheat homologues separated onto sister chromatids in 10.89 % of cells.The plants F2 karyotypes were marked with aneuploidy not only of chromosomes 1A and 1Rv, but also of 1D, 2D, 3D, 3B, 3A, 4A, 6D, 6B, 6A, and 7D. Structural changes were observed for the chromosomes of the first homoeologous group (1Rv, 1A, 1D, 1B), as well as for 2B, 5D, 6B, and 7B. The chromosomes 1Rv and 6B often demonstrated aberrations. The types of aberrations were centromeric break, deletions of various sizes, and a changed repeat pSc119.2 localization pattern.

The presence of solar radiation is one of the most important environmental factors, which is required for the optimal growth and development of plants. The absence of it (e.g. in the night period or artificially prolonged darkness) can alter the light-dependent signalling and regulation pathways and may induce new defence responses. Antioxidant enzymes as components of the plant defence system play a crucial role in the detoxification of reactive oxygen species (ROS) induced by several stressors; however, their regulation can be different in the light or in the dark. In this review we summarize the current knowledge about the physiological and molecular aspects of dark-modulated key antioxidant enzymes (superoxide dismutase, catalase, and ascorbate peroxidase) in different plant species and discuss their roles in different developmental processes (seedling growth and development or senescence) and in responses to environmental stresses (cold, chilling, heat, and biotic stress). Moreover, the hormonal regulation of respective gene transcription and the changes in activity of various isoenzymes at subcellular level are also summarized. Based on this knowledge, modification of these antioxidant enzymes may be used to increase the yield and stress tolerance of cultivated plants in the changing environment.

Candidate gene association studies implicate the detection of contributing single nucleotide polymorphism (SNP) for the target traits and have been recommended as a promising technique to anatomize the complex characters in plants. ERECTA gene in plants controls different physiological functions. In this study, we identified SNPs in 1.1 kb partial sequences of TaER-1 and TaER-2 of wheat (Triticum aestivum L.). Thirty-nine SNPs were identified in the coding regions of TaER-1 gene in 33 wheat genotypes, of which 20 SNPs caused non-synonymous mutations while 19 SNPs produced synonymous mutations; while 31 SNPs were located in the coding regions of TaER-2 gene in 26 genotypes, of which 18 SNPs caused non-synonymous mutations and 13 SNPs caused synonymous mutations. In addition, 32 SNPs in TaER-1 and 9 SNPs in TaER-2 were also identified in the non-coding regions. Moreover, the significant genetic associations of SNPs of TaER-1 and TaER-2 genes with carbon isotope discrimination, stomatal conductance, photosynthetic rate, transpiration rate, intrinsic water use efficiency (iWUE), leaf length, leaf width, stomatal density, epidermal cell density, and stomatal index were noted in wheat genotypes. This study confirms the importance of TaER-1 and TaER-2 genes which could improve iWUE of wheat by regulating leaf gas exchange and leaf structural traits. These identified SNPs may play a critical role in molecular breeding by means of marker-assisted selection.

Boron (B) is an essential plant micronutrient. Two major B-transport proteins have been recently identified and partially characterized: BOR1, a high-affinity B efflux transporter involved in xylem loading, and NIP5;1, a plasma-membrane boric-acid channel involved in B uptake. To date, studies of these B transporters have investigated their expression individually (mainly as mRNA), and only in response to variation in B availability (mostly B deficiency); the influence of other factors, such as plant resource status, has not been studied. To address this, we grew geranium (Pelargonium × hortorum cv. Maverick White) plants under ambient or elevated CO₂ concentration, different sub-saturating irradiances, and different B availability. For comparison we also grew three other species (Arabidopsis thaliana, Azolla caroliniana, and Hordeum vulgare) under broad range of B supply. Relative accumulation of BOR1 and NIP5;1 proteins were measured using protein-specific antibodies and Western blotting or ELISA. Elevated CO₂ significantly increased content of NIP5;1, while increases in irradiance increased BOR1 content, but decreased NIP5;1 content. Across species, content of both transporters often decreased with increasing B availability, but sometimes remained unchanged or even increased, depending on CO₂, irradiance, species, or transporter. Content of BOR1 and NIP5;1 was correlated with root proteins, B content, and sugar content (for high CO₂ only), as well as B uptake, but CO₂ and irradiance often affected these relationships. Thus, relative accumulation of BOR1 and NIP5;1 is influenced not only by B content, as expected, but by other environmental factors as well.

Virus-induced gene silencing (VIGS) is a post-transcriptional gene silencing method used for unraveling gene functions. As an attractive alternative to mutant collections or stable transgenic plants, it has been widely used in reverse-genetics studies owing to its ease use and quick turnaround time. Turnip yellow mosaic virus (TYMV) has the ability to induce VIGS in Arabidopsis thaliana. However, the conventional vector construction is difficult and the efficiencies of the infection methods are low. Here, we improved the vector construction and viral infection methods, inserted an inverted-repeat fragment of the phytoene desaturase gene into a TYMV-derived vector by homologous recombination and transformed Brassica rapa with plasmid DNA harboring a cDNA copy of the TYMV genome through particle bombardment. An apparent photobleaching phenotype was detected and efficient VIGS was induced. An 80-bp fragment was sufficient to produce VIGS in leaves, stems, roots, flowers, siliques, and stalks of B. rapa. Because TYMV has a wide host range in Brassica, the VIGS system described here will contribute to the improvement of high-throughput technology and efficient functional research in B. rapa and other Brassicaceae crops.

In transgenic plants, for many applications it is important that the inserted genes are expressed in a tissue-specific manner. This in turn could help better understanding their roles in plant development. Germin-like proteins (GLPs) play diverse roles in plant development and defense responses. In order to understand the functions and regulation of the GLP13 gene, its promoter (762 bp) was cloned and fused with a β-glucuronidase (GUS) reporter gene for transient expression in Arabidopsis thaliana and tobacco (Nicotiana tabacum cv. K326). Histochemical analysis of the transgenic plants showed that GUS was specifically expressed in vascular bundles predominantly in phloem tissue of all organs in Arabidopsis. Further analyses in transgenic tobacco also identified similar GUS expression in the vascular bundles.

Viral resistance can be effectively induced in transgenic plants through their silencing machinery. Thus, we designed nine short hairpin RNAs (shRNA) constructs to target nuclear inclusion protein b (NIb), helper component proteinase (HC-Pro), cylindrical inclusion protein (CI) and viral protein genome linked (VPg) genes of Potato virus Y (PVY^N) and Tobacco etch virus (TEV-SD1). The shRNAs were completely complementary to the genes of PVY^N, and contained 1-3 nt mismatches to the genes of TEV-SD1. To study the specificity of gene silencing in shRNA-mediated viral resistance, the constructs were introduced into tobacco plants. The results of viral resistance assay revealed that these nine kinds of transgenic tobacco plants can effectively induce viral resistance against both PVY^N and TEV-SD1, and the shRNA construct targeting the NIb gene showed higher silencing efficiency. Northern blot and short interfering RNA (siRNA) analyses demonstrated that the viral resistance can be attributed to the degradation of the target RNA through the RNA silencing system. Correlation analysis of siRNA sequence characteristics with its activity suggested that the secondary structure stability of the antisense strand did not influence siRNA activity; 1 to 3 nt 5' end of the sense strand caused a significant effect on siRNA activity where the first base such as U was favourable for silencing; the base mismatch between the siRNA and the target gene may be more tolerated in the 5' end.

In this work, we report the ectopic expression of the Osmyb4 rice gene, encoding the Myb4 transcription factor, in Nicotiana tabacum and Salvia sclarea. Transcriptional analysis of T₂ homozygous tobacco plants overexpressing Osmyb4 revealed that Myb4 activated the transcription of several genes of the phenylpropanoid pathway such as PAL, C4H, 4CL1, 4CL2 (encoding phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4-coumarate: Co A ligase1, 4-coumarate: Co A ligase2). Moreover, the Myb4 increased expression of HQT encoding hydroxycinnamoyl-CoA: quinate transferase, which specifically triggers the accumulation of chlorogenic acid (CGA). In addition, increased acccumulation of rosmarinic acid (RA) was found in transgenic plants of both species. These results open the possibility of using the Osmyb4 gene to increase the production of specific bioactive hydroxycinnamates.