The ultrastructure of leaf mesophyll cells of in vitro cultured Hypericum perforatum L. plants regenerated after cryopreservation was studied. Electron microscopy analysis revealed that the chloroplasts in plants pretreated with abscisic acid and regenerated after cryopreservation were round, with increased amount of starch, rather small volume of the thylakoid system, and destroyed envelope. Plants pretreated with 0.3 M mannitol and cooled at rates of 0.1 or 0.3 °C min^-1 possessed chloroplasts with high starch content that resulted in a reduction of a membrane system. However, the pretreatment with 0.3 M mannitol and cooling at a rate of 0.2 °C min^-1 was the best as chloroplast ultrastructure resembled the controls regenerated without cryopreservation.

A glutathione S-transferase (GST) gene cloned from the lepidopteran spruce budworm, Choristoneura fumiferana Clem. was transformed into the model plant Arabidopsis thaliana. The CfGST-transgenic and wild-type A. thaliana were subjected to 4 and 10 °C for 48 h and their cold resistance was studied. The GST activity of the transgenic plants was 46.6 and 35.7 % higher than that of the wild-type plants after 48 h under 4 and 10 °C, respectively. Relative membrane permeability and malondialdehyde content in the transgenic plants were lower while contents of the chlorophyll and proline were higher than those in the wild-type plants under 4 and 10 °C. The survival rate of the transgenic plants was 43.7 % for 24 h under 0 °C, while survival rate of wild-type plants was 28.3 %. The results indicated that the insect GST could enhance cold resistance in the transgenic A. thaliana.

Excess radiation is one of frequent natural environmental stresses that plants have to cope with on a daily basis. Therefore, plants have evolved many short- and long-term mechanisms to acclimate to high irradiance and tolerate it. Ureides, generated from purine degradation, have been proposed as compounds involved in environmental stress responses, including altered irradiance. In the present study, high irradiance was used to investigate ureide content and gene expression in Arabidopsis thaliana. Arabidopsis plants shifted to high irradiance showed high content of a specific ureide compound, allantoin. The accumulation of allantoin was associated with increased expression of uricase, an enzyme involved in its production. When an Arabidopsis mutant (aln-3), which constitutively accumulates elevated amounts of allantoin, was exposed to high irradiance, mutant plants demonstrated enhanced tolerance to the stress conditions compared to the wild-type plants. Our results provide evidence that accumulation of the allantoin might contribute in plants response to increased growth irradiance.

Leek is an economically important vegetable. In model plants, the CONSTANS (CO) and CONSTANS-like (COL) genes play central roles in plant flowering modulation. However, none of leek CO homolog has been identified, because of limited gene resources obtained in this crop. Here, we reported the transcriptome analysis of leek, along with the identification of putative leek CONSTANS-like (COL) (ApCOL) genes. A total of 189 713 non-redundant transcripts were de novo assembled by using about 128.9 million clean sequence reads, of which, 48 621 were achieved for functional annotation. Thereafter, the search for putative ApCOL genes against the assembled transcripts was performed, and 17 genes were identified. The 17 putative ApCOL proteins, together with 16 function-known COL proteins published for other species, were subjected to phylogenetic analysis and divided into four groups. Some putative ApCOL members showed high sequence similarity with published COL proteins involved in flowering regulation. Expression analysis revealed that, among the 17 putative ApCOL genes, eight, two, and three genes showed higher expression in leaves, cauloids, and roots, respectively. The discovery of putative ApCOL genes and the characterization of their expression patterns will provide a basis for future clarification of their functions in leek growth and development.

The gene NCED1 encodes 9-cis-epoxycarotenoid dioxygenase, which catalyzes oxidative cleavage of 9-cis-epoxycarotenoids neoxanthin and violaxanthin to xanthoxin, a key step in the biosynthesis of abscisic acid in higher plants. In the present study, the complete NCED1 of 1 917 bp was cloned and characterized from rice (Oryza sativa L. cv. N22) as no earlier reports were available for its characterization from indica cultivar. The NCED1 had no intron and encoded a protein of 639 amino acids with a predicted molecular mass of 68.62 kD and pI of 6.07. The aliphatic index and grand average of hydropathicity were found to be 77.04 and -0.148, respectively. Multiple alignment analysis revealed that the sequence shared a high identity with the Oryza sativa japonica group (100 %) followed by Triticum aestivum (90 %), Hordeum vulgare (90 %), and Zea mays (89 %). The enzyme had a RPE65 domain of 476 amino acid residues. The RPE65 domain requires Fe(II) as a cofactor coordinated with 4 histidine residues and 3 glutamic acid residues. The phylogenic tree shows that NCED1 of japonica rice and NCED1 of indica rice were in the same group. They might have been evolved from a common ancestor. Analysis with a PSORT III tool shows that NCED is a chloroplastic protein. The real-time quantitative PCR and RNA-sequencing studies show that the expression of NCED1 was progressively reduced with increasing water stress, and a negative correlation between expression of OsNCED1 and severity of stress was established. Further, NCED1 expression negatively correlated with abscisic acid (ABA) accumulation under water stress whereas in some other species its expression increased along with ABA accumulation. This might be due to feedback inhibition of the ABA biosynthesis in rice.

Growth responses of the moderately salt-tolerant velvet ash (Fraxinus velutina) and salt-sensitive poplar (Populus × euramericana) were investigated under heterogeneous root zone salinity. The salinity treatments imposed on the two root zones (lower-higher) were 137-137 (uniform), 103-171, 68-205, 34-239, and 0-273 mM NaCl for velvet ash, and 51-51 (uniform), 34-68, 17-85, and 0-103 mM NaCl for poplar. The leaf gas exchange of the plants was measured one month after these treatments were implemented, and the plants were sampled 75 d after treatment to measure other physiological parameters. Net photosynthetic rate, transpiration rate, total biomass, and fine root compensatory growth increased as the difference in salinity between the two root zones (i.e., salinity heterogeneity) increased in velvet ash. These parameters showed no significant difference among the treatments in poplar. The leaf Na⁺ content was lower under heterogeneous salinity than under uniform salinity in both tested species. The leaf proline content in velvet ash decreased under heterogeneous salinity compared to that under uniform salinity, whereas that of poplar increased. The soluble sugar content of velvet ash leaves increased under heterogeneous salinity, whereas no changes were observed in poplar. The increased fine root biomass in the lower salinity zone promoted velvet ash growth by decreasing the leaf Na⁺ and Cl^- content under heterogeneous salinity. The poplar's undifferentiated root distribution and gas exchange in response to the heterogeneous salinity were attributed to its salt sensitivity.

We compared C₃ and CAM (crassulacean acid metabolism) states in Mesembryanthemum crystallinum, a facultative CAM species, with respect to the involvement of phosphoenolpyruvate carboxylase (PEPC) and nitrogen metabolismrelated enzymes in plant response to Botrytis cinerea infection. The enzyme activities were monitored both in pathogeninoculated 2^nd leaf pair and non-inoculated 3^rd leaf pair. The control activities of most studied enzymes were dependent on the mode of photosynthesis. Compared to C₃ plants, those performing CAM exhibited higher PEPC, nitrate reductase (NR), and deaminating glutamate dehydrogenase (NAD-GDH) activities but lower glutamine synthetase (GS) and alanine aminotransferase (ALT) activities. Regardless of the mode of photosynthetic carbon assimilation, the plants responded to infection with enhancement of PEPC and inhibition of NR activities in the inoculated leaves. Whereas the activity of GS remained unaffected, those of all glutamate-yielding enzymes, namely ferredoxin-dependent glutamate synthase (Fd-GOGAT), aspartate aminotransferase (AST), ALT, and aminating glutamate dehydrogenase (NADHGDH) were altered after infection. However, the time-course and extent of the observed changes differed in C₃ and CAM plants. In general, CAM plants responded to infection with an earlier increase in PEPC and Fd-GOGAT activities as well as later inhibition of NR activity. Contrary to C₃ plants, in those performing CAM the activities of PEPC, Fd-GOGAT, NADH-GDH, and AST in the non-inoculated 3^rd leaf pair were similarly influenced by infection as in leaves directly inoculated with the pathogen. This implies that the local infection induced an alteration of carbon/nitrogen status in healthy upper leaves. This reprogramming resulting from changes in PEPC and nitrogen metabolism-related enzymes was C₃- and CAM-specific.

Osmotic stress causes a series of morphological, physiological, biochemical, and molecular changes that alters plant growth, development, and productivity around the globe. Phytohormones, nutrients, and transcription factors may induce adaptive responses to osmotic stress in plants. We evaluated the effect of osmotic stress induced by 18.5 % polyethylene glycol (PEG) or 100 mM NaCl on growth, content of abscisic acid (ABA), chlorophyll (Chl), sodium, and potassium, and the expression of multifunctional NAC transcription factors in rice cultivars (the salt-tolerant Cotaxtla and salt-sensitive Tres Ríos). The PEG and NaCl decreased shoot height and increased ABA content in both cultivars, and reduced root length in cv. Tres Ríos. The PEG increased Chl content in cv. Cotaxtla leaves. NaCl reduced shoot K⁺ content in cv. Tres Ríos and increased shoot and root Na⁺ content in both cultivars, thus resulting in a decreased K⁺/Na⁺ ratio. Of the 57 NAC genes evaluated, two of them were repressed (Os10g42130 and Os07g04560) and two other induced (Os02g34970 and OsNAC10) in cv. Cotaxtla in response to PEG, whereas three of them were repressed (Os10g42130, Os07g04560 and Os08g10080), and six induced (Os02g56600, Os02g34970, Os11g08210, Os05g34830, OsNAC6, and OsNAC10) in response to NaCl. In the cv. Tres Ríos, we found two genes repressed (Os10g42130 and Os07g04560), and five induced (Os08g33910, Os03g60080, Os06g51070, OsNAC6, and OsNAC10) in response to PEG, while only two genes were repressed (Os10g42130 and Os07g04560) but 13 induced (Os03g21060, Os08g39110, Os03g60080, Os01g15640, Os06g51070, Os09g33490, Os04g40130, Os12g29330, Os02g36880, Os11g08210, Os05g34830, OsNAC6, and OsNAC10) by NaCl. Osmotic stress affected more severely cv. Tres Ríos than cv. Cotaxtla plants. These different responses might be regulated by ABA and NAC transcription factors.

Brassinosteroids (Brs) have drawn wide attention due to their protective role against toxicity of heavy metals in plants. To better understand the role of Br in arsenic (As) and cadmium (Cd) uptake by rice plants, a hydroponic experiment was conducted to investigate the combined effect of 24-epibrassinolide (Br24) or 28-homobrassinolide (Br28) and iron plaque (IP) on As and Cd uptake and accumulation in rice seedlings. Six-week-old seedlings were sprayed with 0.2 or 0.02 μM Br24 or Br28 and grown in nutrient solution for 3 d, and then 20 or 60 mg Fe²⁺ dm^-3 (Fe20 and Fe60) was used to induce root IP formation for 3 d. These seedlings with or without Br and with or without IP were exposed to solution containing 0.5 mg dm^-3 As^III or Cd for 9 d. The results showed that rice growth decreased when Br24 were applied, but it increased when combination of Br24 and IP was applied. Fe concentrations in dithionite-citratebicarbonate (DCB) extracts were increased after 0.2 or 0.02 μM Br24 application in the absence of IP, but decreased by Br24 in the presence of IP. In the absence of IP, As and Cd content in leaves was significantly reduced by 0.02 μM Br24 and 0.2 μM Br28, respectively. The As content in leaves was also reduced by the combination of 0.02 and 0.2 μM Br28 and IP, and the Cd content in leaves was reduced by the combined effect of 0.2 μM Br24 and IP. These results indicate that Br24 and Br28 could impede As and Cd accumulation, and the interactions between Br and IP may have a potential in restricting the transport of As and Cd into rice shoots.

Gibberellic acid (GA) promotes cotton fiber cell elongation under in vitro culture conditions and GA signal transduction is mediated by DELLA proteins. Our laboratory has cloned several DELLA genes from cotton and generated transgenic lines in Arabidopsis over-expressing the DELLA gene (GhRGL) and the DELLA-domain deletion mutant gene (Ghrgl). Comparative transcriptome profiling was performed on Arabidopsis transgenic lines over-expressing both GhRGL and Ghrgl. KEGG pathway analysis indicated that the differential genes participated in many important pathways, such as response to gibberellic acid, fatty acid metabolism, etc., and the expression patterns of 93 genes were validated by RT PCR in all transgenic lines and the wild-type plants. Gene ontology annotation identified that these genes were involved in sucrose synthesis, actin nucleation, root hair development, and various hormone signal responses.

Sugars are important molecules that function not only as primary metabolites, but also as nutrients and signal molecules in plants. The sugar transport protein genes family SWEET has been recently identified. The availability of the Dendrobium officinale and Phalaenopsis equestris genome sequences offered the opportunity to study the SWEET gene family in this two orchid species. We identified 22 and 16 putative SWEET genes, respectively, in the genomes of D. officinale and P. equestris using comprehensive bioinformatics analysis. Based on phylogenetic comparisons with SWEET proteins from Arabidopsis and rice, the DoSWEET and PeSWEET proteins could be divided into four clades; among these, clade II specifically lacked PeSWEETs and clade IV specifically lacked DoSWEETs, and there were orthologs present between D. officinale and P. equestris. Protein sequence alignments suggest that there is a predicted serine phosphorylation site in each of the highly conserved MtN3/saliva domain regions. Gene expression analysis in four tissues showed that three PeSWEET genes were most highly expressed in the flower, leaf, stem, and root, suggesting that these genes might play important roles in growth and development in P. equestris. Analysis of gene expression in different floral organs showed that five PeSWEET genes were highly expressed in the column (gynostemium), implying their possible involvement in reproductive development in this species. The expression patterns of seven PeSWEETs in response to different abiotic stresses showed that three genes were upregulated significantly in response to high temperature and two genes were differently expressed at low temperature. The results of this study lay the foundation for further functional analysis of SWEET genes in orchids.

Heterotrimeric guanine-nucleotide-binding proteins (G-proteins) play important roles in signal transduction and regulate responses to various stresses. Although G-protein signaling pathways have been extensively identified and characterized in model plants, there is little knowledge in non-model and especially in woody plants. Mulberry is an economically and ecologically important perennial tree, which is adaptable to many environmental stresses. In this study, we identified and cloned six G-protein genes including one Gα, one Gβ, two Gγ, one RGS (regulator of G-protein signaling protein) and one RACK1 (receptor for activated C kinase 1) involved in G-protein signaling. Sequence and phylogenetic analysis revealed that Morus G-proteins are evolutionarily conserved compared with those of other plants. A real-time quantitative reverse transcription polymerase chain reaction analysis showed that Morus G-protein signaling genes were ubiquitously but differentially expressed in various tissues. The expression of all of these genes was affected by abiotic stresses and signal molecules, which indicated that Morus G-protein signaling may be involved in environmental stress and defense responses.

Elymus nutans is an important alpine perennial forage of the Pooideae subfamily, that can survive subzero temperatures. To understand the molecular mechanisms underlying cold tolerance in E. nutans, we performed the transcriptional analysis by RNA-Seq in two genotypes, the tolerant Damxung (DX) and the sensitive Gannan (GN), under cold stress. The new E. nutans transcriptomes comprised 200 520/200 836 and 181 331/211 973 transcripts in leaves/crowns of DX and GN, respectively. More cold-stress-related genes were identified in leaves than in crowns of both genotypes throughout the whole cold stress. The most prominent functional category in leaves of both genotypes at 3 h of stress was transcriptional regulation. Brassinosteroid and jasmonic acid mediated signalling pathways play central roles in regulating downstream protective responses in DX after 24 h of cold stress. Prolonged cold stress caused more severe transcriptome responses in crowns and leaves of DX compared to GN. The most significant transcriptomic changes in both genotypes were associated with the response to abiotic stresses and the oxidation-reduction processes, implying reprogramming of the cellular metabolism as an adaptation to cold stress. This study reveals mechanisms of genotype- and organ-specific cold stress response in E. nutans and thus provides a basis for future breeding strategies aimed at improving the tolerance of cold-sensitive plants.

WRKY transcription factors (TF) family is involved in a huge variety of plant processes, including seed germination, plant development, phytohormone signalling, and defence against both biotic or abiotic stresses. In this work, WRKY TF family has been characterized in citrus. In a first experiment, the relative expression of CsWRKYs was analyzed in shoots and roots of plants treated with abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA) under in vitro conditions. Expression of CsWRKYs was also determined in roots of commercial citrus rootstocks subjected to osmotic and salt stresses. A total amount of 50 CsWRKYs has been found and devided into different groups of WRKY family according to the WRKY domain sequences. In response to the applications of phytohormones, the highest differences were observed in roots, and it was found that ABA and SA generally repressed CsWRKYs expressions, but MeJA induced their overexpression. Osmotic stress repressed the expression of most of the CsWRKYs, whereas salt stress induced their expression. Moreover, salt stress induced higher increase in CsWRKY expressions in the tolerant rootstock Citrus macrophylla than in the sensitive rootstock Carrizo citrange, suggesting that these TFs may play an important role in response to this stress.

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.