The halophyte Thellungiella salsuginea is a new model plants due to its small genome size, short life cycle, and copious seed production. Although T. salsuginea shares a high sequence identity with its close relative Arabidopsis thaliana, it shows a greater tolerance to salinity, drought, freezing, heat, and cold. To elucidate the mechanism of abiotic stress resistance in T. salsuginea, we characterized its cytosolic Apx1 gene (TsApx1) and established A. thaliana transgenic lines overexpressing TsApx1. Under 300 mM NaCl, the content of H₂O₂, malondialdehyde, and proline were lower and the activities of superoxide dismutase, catalase, glutathione peroxidase, and ascorbate peroxidase were all higher in the transgenic plants overexpressing TsApx1 (35S:TsApx1-GFP) than in the wild-type plants. The atapx1 mutant plants of A. thaliana had a NaCl/mannitol-sensitive phenotype. The ectopic expression of TsApx1 in the atapx1 mutant effectively remedied the phenotype. These results suggest that TsApx1 plays an important role in scavenging reactive oxygen species in the cytoplasm under salinity or drought. Although TsApx1 in T. salsuginea was constantly expressed at a high level, this gene was clearly inducible. In summary, the high constitutive expression and rapid induction of TsApx1 may contribute to the tolerance to abiotic stresses in T. salsuginea.

Gamma-aminobutyric acid (GABA) is a non-protein amino acid that accumulates in a number of plant species under various environmental stresses. In this paper, the ability of applied GABA for the alleviation of NaCl stress was investigated in view of growth parameters, gas exchange, photosynthetic pigments, chlorophyll fluorescence, activities of antioxidant enzymes, malondialdehyde (MDA) content, and electrolyte conductivity (REC) in wheat seedlings. Germination rate and shoot dry mass decreased with an increasing NaCl concentration and this decrease was less pronounced when 0.5 mM GABA was applied. In the NaCl-treated seedlings, exogenous GABA partially enhanced photosynthetic capacity and antioxidant enzyme activities and decreased MDA content and REC. Therefore, GABA reduced the impact of salinity on the wheat seedlings.

Soybean is stress-sensitive crop that exhibits markedly reduced growth under flooding and drought conditions. Three S-adenosylmethionine synthetases (SAMs) proteins were identified as flooding and drought responsive proteins in soybean using a proteomic technique. To better understand the role of these SAMs proteins in soybean under flooding and drought stresses, temporal, organ, and stress specificities were examined at mRNA and enzyme activity levels. The activity of SAMs decreased in response to the flooding, however, it was not significantly changed by NaCl, cold, gibberellic acid, and calcium in soybean roots. The activity of SAMs was induced in roots and hypocotyls under drought. The mRNA expression of the S-adenosylmethionine synthetase (SAMs) family was down-regulated in root tips and roots under the flooding and the drought, and SAMs 1 and SAMs 2 were down-regulated in roots under both stresses. A gene 1-aminocyclopropane-1-carboxylate synthase was up-regulated in root tips, roots, and hypocotyls under drought, however, it was not changed in root tips and roots under the flooding. In addition, 1-aminocyclopropane-1-carboxylate oxidase was induced in root tips under flooding and drought. These results suggest that SAMs was involved in the response to the flooding and drought and it might affect ethylene biosynthesis in soybean.

MicroRNAs (miRNAs) are small non-coding RNAs that play crucial regulatory roles in diverse developmental processes via cleavage or translational inhibition of their target mRNAs. Although a growing number of miRNAs and their targets have been predicted and discovered via experimentation in many plants, little is known about conserved miRNAs and their target genes in Pinus densata. In the present study, the conserved miRNAs, miR171 and miR482, from Pinus densata were characterized. Analysis of miR171 and miR482 reveal that these miRNAs were highly conserved in other plant species. In addition, the precursors of miR171 and miR482 were validated by real time-PCR and sequencing. Using real-time quantitative PCR, miR171 and miR482 as well as their corresponding targets were found to be differentially expressed in needles, stems, and roots of Pinus densata. Furthermore two target genes, one GRAS family transcription factor protein gene and one nucleotide-binding site leucine-rich repeat (NBS-LRR) resistance protein gene, were experimentally verified to be the targets of pde-miR171 and pde-miR482, respectively, using RNA ligase-mediated 5'-rapid amplification of cDNA ends (RLM-RACE).

Activities of phenylalanine (Phe) biosynthetic enzymes chorismate mutase (CM) and arogenate dehydratase (ADT) and of phenylalanine ammonia lyase [PAL, an enzyme that directs Phe towards capsaicinoid (CAP) synthesis] were analyzed during Capsicum chinense Jacq. (habanero pepper) fruit development. A maximum CM activity coincided with a maximum CAP accumulation. However, ADT exhibited two activity peaks, one during the early phase (10 - 17 days post-anthesis, DPA) and another during the late phase (35 - 37 DPA); only the latter coincided with CAP. Interestingly, PAL activity was inversely related to CAP accumulation; lower activities coincided with a maximum CAP content. These results suggest the operation of a control mechanism that coordinated Phe synthesis and its channeling towards CAP synthesis during the course of fruit development.

Development of transgenic plants by introducing defense genes is one of the strategies to engineer disease resistance. Transgenic ASD16 rice plants harbouring rice chitinase chi11 gene, belonging to a PR-3 group of defense gene conferring sheath blight (Rhizoctonia solani Kuhn) resistance, were used in this study. Three T₂ homozygous lines (ASD16-4-1-1, 5-1-1, and 6-1-1) were identified from seven putative (T₀) transgenic lines expressing chi11 using Western blotting analysis. The inheritance of sheath blight resistance in those lines was studied over generations. The stability of chi11 expression up to T₄ generation in all the three homozygous lines was proved by Western blot and the stability of sheath blight resistance in the homozygous lines was proved up to T₄ generation using detached leaf and intact leaf sheath assays. Among the three homozygous lines tested, ASD16-4-1-1 showed consistent results in all the generations and gave a better protection against the sheath blight pathogen than the other two lines.

We tested the capability of plants to utilize a mixture of amino acids and peptides as the exclusive source of nitrogen. The aim of this study was to find out how such a nutrition affected plantlet growth, photosynthetic performance, and N assimilation metabolism in tobacco (Nicotiana tabacum L., cv. Petit Havana SR1) grown in vitro. Plantlets grown in a casein hydrolysate-supplemented (CA) medium were compared to plantlets grown in a complete Murashige-Skoog (MS) medium, plantlets grown in an ammonium-deficient medium (N1), or plantlets grown in a nitrate-reduced medium (N2). In addition, the plantlets were grown in the presence or absence of 1.5 % (m/v) saccharose as an additional carbon source. Casein hydrolysate, similarly as inorganic N limitation, reduced generally plantlet growth, whereas no significant effects were observed on photosynthetic parameters evaluated by chlorophyll a fluorescence. Although addition of saccharose stimulated the plantlet growth particularly in the MS, it showed a rather negative influence both on the growth and on the photochemical efficiency of photosystem II in the plantlets grown in the CA and N1. The activities of enzymes involved in N assimilation, such as nitrate reductase (NR) and glutamine synthetase (GS), were lower in the plantlets grown in the CA, N1, and N2, both in leaves and in roots. On the other hand, glutamate synthase and glutamate dehydrogenase were employed by the plantlets grown in the CA. The presence of saccharose in the growth medium stimulated mainly NR and GS activities in the MS grown plantlets, whereas enzyme activities of the plantlets grown on the N1, N2, and CA were not significantly influenced. We proved that the tobacco plantlets can utilize casein hydrolysate as the sole source of N particularly during their photoautotrophic cultivation. Contrary to positive effects of photomixotrophic nutrition for the MS grown plantlets, exogenous sugar seemed to diminish the ability of the casein hydrolysate-supplemented plantlets to utilize efficiently the additional C source.

A photoperiod-sensitive soybean [Glycine max (L.) Merr] cv. ZhongDou 24 (ZD24) exhibiting delayed flowering when grown under long-days (LD, a 16-h photoperiod) was used to identify the genetic control of flowering delay. A differential expression profiling technique enabled identification of a gene fragment that was up-regulated under LD. This fragment was homologous to a gene encoding methionine synthase (MS) in soybean and was named GmMS. The RNA content confirmed that GmMS was expressed in roots, stems, and leaves of soybean grown under LD. The highest expression was in stems. Full length GmMS, encoding 763 amino acids, was transferred into tobacco plants. The ectopic expression of GmMS in tobacco resulted in delayed flowering. Other effects included stunting, an increased MS activity and methionine content, a higher content of alcohol-soluble proteins and of chlorophylls, and a lower content of anthocyanins.

Extracellular ATP (eATP) has been considered as signalling compound to mediate several physiological processes. Here we show that eATP played a role in alleviating the salicylic acid (SA)-induced inhibition of cell viability and respiration in tobacco (Nicotiana tabacum L. cv. Bright Yellow-2) suspension cells. Exogenous SA at higher concentrations (0.05, 0.1, 0.3, 0.5, or 0.7 mM) caused a significant reduction in respiratory O₂ uptake or cell viability. The addition of exogenous ATP alleviated the SA-induced reductions in cell viability and respiration, but the effect was dependent on the concentrations of either exogenous SA or ATP. Further study shows that the alleviative effects of exogenous ATP were abolished by the addition of GdCl₃ (an inhibitor of Ca²⁺ channels) or EGTA (a Ca²⁺ chelator). These results suggest that this role of extracellular ATP could be related to a Ca²⁺ signalling pathway.

In this study, proteome and activities of glutathione (GSH)-related enzymes were investigated in detached leaves of Arabidopsis thaliana treated with ochratoxin A (OTA) alone or supplemented with buthionine sulfoximine (BSO, a specific inhibitor of the first step in GSH biosynthesis). A comparative proteomic study using two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization-time of flight tandem mass spectrometry (MALDI-TOF/TOF MS/MS) identified 12 differentially expressed proteins mainly involved in GSH metabolism, energy metabolism, sugar metabolism, and photosynthesis. The treatment with OTA significantly enhanced the activities of glutathione-S-transferase (GST) and glutathione reductase (GR) through up-regulating the corresponding genes (GSTF7, GR1), an the diminishing effect of BSO on them counteracted the results. However, both OTA and BSO decreased the activity of ascorbate peroxidase (APX), and OTA also decreased the monodehydroascorbate reductase (MDHAR) and glutathione peroxidase (GPX) activities. Briefly, the OTA-induced phytotoxicity to the A. thaliana detached leaves was increased slightly by addition of BSO, and the fluctuation in GSH synthesis, GSH metabolism and disorder of cellular metabolism happened.

Coleus forskohlii (syn. Plectranthus barbatus) is a widely used medicinal plant and its main bioactive constituents are diterpenes forskolin and isoforskolin. The present study aimed to construct a cDNA library to identify expressed sequence tags related to terpene biosynthesis in C. forskohlii. We constructed a high quality normalized full-length cDNA library which reached the requirements (abundance, integrity, and library content) for isolating full-length genes. A total of 4 224 cDNA clones were sequenced and 2 394 unigenes were assembled with an average unigene size of 753 bp. A total of 2 100 (87.7 %) unigenes were functionally classified using gene ontologies, and 1 716 (71.7 %) unigenes were assigned to establish pathway associations in KEGG mapings. Notably, 64 unigenes putatively participated in the biosynthesis of secondary metabolites, in which 17 unigenes were identified that might be involved in the biosynthesis of the terpenoid backbone and monoterpenes, diterpenes, and triterpenes.

The effects of copper oxide nanoparticles (CuONPs) on germinating seedlings of green pea (Pisum sativum L.) were studied. The seedlings were grown in a half-strength Murashige and Skoog semisolid medium containing 0, 50, 100, 200, 400, and 500 mg dm^-3 CuONPs for 14 d under controlled growth chamber conditions. Exposures to 100, 200, 400, and 500 mg dm^-3 CuONPs significantly reduced plant growth (shoot and root lengths) and increased reactive oxygen species (ROS) generation and lipid peroxidation. Gene expression study using real-time polymerase chain reaction showed no significant change in the expression of genes coding CuZn-superoxide dismutase (CuZnSOD), catalase (CAT), and ascorbate peroxidase (APX) in shoots. However in roots, a significant increase in the expression of the CuZnSOD gene was observed under the exposures to 100, 200, 400, and 500 mg dm^-3 CuONPs, in the expression of the CAT gene under 100 and 200 mg dm^-3 CuONPs, and in the expression of APX under 200 and 400 mg dm^-3 CuONPs.

Tospoviruses are devastating plant viruses causing severe economic losses in a diverse range of crops worldwide. Here, we describe the development and evaluation of an RNA interference (RNAi) broad-spectrum virus resistance strategy based on a unique and short hairpin-RNA-generating construct (pNhpRNA). This construct was designed from a region of the nucleocapsid gene (N) of Tomato spotted wilt virus (TSWV) that showed a high sequence identity to the corresponding region in the related species Groundnut ringspot virus (GRSV) and Tomato chlorotic spot virus (TCSV). To test the effectiveness of the pNhpRNA construct, we developed a silencing reporter assay based on three fusion proteins in which the complete viral N gene sequence from each of the three tospoviruses was fused in frame to the green fluorescent protein (GFP) sequence. Co-agroinoculation of these constructs with pNhpRNA into leaves of Nicotiana benthamiana resulted in a strong silencing phenotype determined by GFP decay and suppression of the three N genes at the RNA and protein levels. To test the potential of the pNhpRNA construct to generate virus-resistant plants, we infiltrated the whole shoots of N. benthamiana with pNhpRNA. When these infiltrated plants were mechanically inoculated with the mentioned viruses 100, 70, and 60 % resistance phenotypes to TSWV, GRSV, and TCSV, respectively, were observed. The induction of a broad tospovirus resistance with a simple construct and a minimized off-target effect are the main contributions of pNhpRNA.

In shaded wheat (Triticum aestivum L.) leaves, the suppression of blue radiation (BR) triggers senescence. This phenomenon is correlated to an increase in oxidative stress symptoms and a decrease of catalase (CAT) activity, among other traits. Previous data suggest that the radiation signal transduction pathway may involve changes in Ca²⁺ and H₂O₂ homeostasis. For better a understanding of the interaction among the spectral composition of radiation, Ca²⁺ availability, and the antioxidant metabolism in the regulation of shade-induced senescence, detached wheat leaves were placed in a growth chamber and exposed to either blue (B, high BR transmittance) and/or green (G, very low BR transmittance) Lee® filters in the absence or presence of 0.8 mM verapamil (a Ca²⁺ channels blocker), 4.0 mM EGTA (a Ca²⁺chelator), or 8.0 mM 3-amino-1,2,4-triazole (a CAT inhibitor). At defined time points, the leaf samples were analyzed for changes in chlorophyll content, specific activities of CAT, ascorbate peroxidase (APX), and guaiacol peroxidase (POX), CAT isozymes, and gene expression of CAT1, CAT2, and two senescence markers (TaSAG1 and TaSAG3). BR transmittance decreased the chlorophyll degradation rate and SAG genes expression either in leaves continuously exposed under the B filter, as well as in leaves previously exposed under the G filter. The effect of BR was associated with the maintenance of a high CAT (but not APX and POX) activity, and it was suppressed either in the presence of 3-AT or when Ca²⁺ availability was decreased. BR altered the CAT activity both at the transcriptional and at the posttranscriptional level. Nevertheless, different responses of CAT isozymes and CAT genes expression profiles to specific treatment combinations indicate that they differed in their regulatory pathways.

A segregating F4 population from the cross between drought sensitive (Yecora Rojo) and drought tolerant (Pavon 76) genotypes was made to identify molecular markers linked to a wheat (Triticum aestivum L.) abscisic acid (ABA) content at two water regimes. The parents and 150 F₄ lines were evaluated phenotypically for drought tolerance using two irrigation treatments [0.25 and 0.75 m³(H₂O) m^-2(soil)]. Forty different target region amplification polymorphism (TRAP) primer combinations, 98 different sequence-related amplified polymorphism (SRAP) primer combinations, and 400 simple sequence repeat (SSR) primers were tested for polymorphism among the parental genotypes and the F₄ lines. Seven loci in the F₄ lines treated with the drought stress were identified. Single quantitative trait loci (QTLs) were located on chromosomes 1B, 2A, 3A, 5D, and 7B and each of them explained from 15 to 31 % of phenotypic variance with a LOD value of 7.2 to 15.7. Five QTLs were located on chromosome 4A and six QTLs on chromosome 5A. In control (well-watered) F₄ lines, two QTLs were mapped on chromosome 3B and one QTL on each chromosome 5B and 5D. Statistically the most significant groups of QTLs for the ABA content were identified in the regions of chromosomes 3B, 4A, and 5A mostly near to Barc164, Wmc96, and Trap9 markers. Therefore, these markers linked to QTLs for the drought-induced ABA content can be further used in breeding for drought tolerance in wheat.

Drought stress presents a considerable threat to the global crop production. As a dominant source of vegetarian diet, cereals and grain-legumes remain crucial to meeting the growing dietary demands worldwide. Therefore, breeding cultivars of these staple crops with enhanced drought tolerance stands to be one of the most sustainable solutions to enhance food production in changing climate. Given the context, a more focused survey of environment-defined germplasm sets is imperative to comprehend such adaptive traits. In parallel, uncovering the genetic architecture and the molecular networks that collectively contribute towards drought tolerance is urgently required through rationally combining large-scale genomics, proteomics, and metabolomics data. Also, attention needs to be directed to reasonably quantify the epistatic as well as environmental influences, thereby warranting deployment of analyses like metaquantitative trait loci (QTL) that encompass multiple environments and diverse genetic backgrounds. Further, innovative techniques like genomic selection (GS) and genome wide association study (GWAS) would help to capture the quantitative variation underlying drought tolerance. Equally importantly, integration of physiological traits-based techniques with ever-evolving 'omics' technologies and the new-generation phenotyping platforms will be of immense importance in advancing our existing knowledge about the genetically-complex and poorly-understood phenomena, such as plant drought response, and a deeper understanding would likely to provide a great impetus to the progress of crop breeding for drought tolerance.

The effects of proline and/or glycine betaine (GB) application on growth, photosynthetic pigments, H₂O₂ content, and activities of antioxidant enzymes in rice (Oryza sativa L. cv. KDML105) under salt stress were investigated. The H₂O₂ content and the activities of superoxide dismutase (SOD), glutathione reductase (GR), and ascorbate peroxidase (APX) but not catalase (CAT) increased under salinity. Under 160 mM NaCl, the CAT activity was maintained on the pre-stress level in the presence of proline, whereas in the presence of GB, the GR activity increased more than without GB application. A co-application of 30 mM proline and 1 mM GB did not reduce the increase in H₂O₂ caused by the NaCl stress more than applying each of the osmoprotectants and no synergistic effect on the antioxidant enzymes was observed. However, the application of both the osmoprotectants was the most effective in alleviating degradation of photosynthetic pigments.

Strawberry (Fragaria × ananassa) contains anthocyanins which are important secondary metabolites and key contributors to the antioxidant capacity and nutritional value of the fruit. Anthocyanin biosynthetic genes have been identified. However, the detailed mechanism responsible for anthocyanin accumulation and regulation of biosynthetic genes during strawberry fruit ripening remain unclear. In the present study, we examined the effect of a Fragaria × ananassa myeloblastosis 1 homolog, FaMYB1, on anthocyanin accumulation in the strawberry fruit receptacle. Expression analysis shows that FaMYB1 transcripts increased in response to irradiance but not to abscisic acid treatments. Down-regulation of FaMYB1 was achieved in planta using Agrobacterium-mediated RNA interference (RNAi). As a result, FaMYB1-RNAi fruits exhibited a significant increase in anthocyanin content. Conversely, overexpression of FaMYB1 resulted in a decrease in anthocyanin content. Overexpression of FaMYB1 also significantly reduced expression of genes encoding anthocyanidin synthase and flavonoid glycosyltransferase, whereas down-regulation of FaMYB1 resulted in a significant decrease in the amount of transcripts of leucoanthocyanidin reductase. These data suggest that FaMYB1 might negatively control anthocyanin biosynthesis in the strawberry fruit at the branching-point of anthocyanin/proanthocyanidin biosynthesis.

Litchi (Litchi chinensis Sonn.) is an important tropical and subtropical evergreen woody fruit tree, and it has been shown that nitric oxide (NO) could promote litchi flowering. NO responsive genes of litchi (cv. Nuomici) primordia were identified through a suppression subtractive hybridization (SSH) library screen. We obtained 1 563 expressed sequences tags (ESTs) that were enriched in the NO treated inflorescence primordia. We then used a reverse Northern analysis to identify 728 true NO responsive ESTs, the sequences of which have been further analyzed. They represent 70 litchi unique genes that could be classified into 9 categories: 14 % of them were involved in transport facilitation, 7 % in transcription regulation, 9 % in stress response, 7 % in sugar metabolism, 9 % in secondary metabolism, 10 % in intracellular signalling, and 44 % in other metabolism, whereas 11 % were genes with unknown functions, and 7 % were genes with no hit found. Next, we performed a real-time quantitative polymerase chain reaction (RT-qPCR) to determine the expression of selected candidate genes during a time-course of NO treatment and of normal floral tissue development.

Apple (Malus × domestica Borkh.) is a perennial woody plant that undergoes a period of dormancy (in cv. Jonathan between late September and mid-December) to survive freezing temperatures of winter. DORMANCY-ASSOCIATED MADS-BOX (DAM) genes play important roles in the regulation of growth cessation and terminal bud formation in peach. To understand the role of DAM orthologs in apple, we isolated and characterized four DAM-like genes (designated as MdDAMa, MdDAMb, MdDAMc, and MdDAMd) and monitored their expression in apical buds throughout the season by real-time quantitative polymerase chain reaction analyses. The transcription of MdDAMa peaked in October and that of MdDAMc was elevated from August to October, whereas MdDAMb and MdDAMd were practically undetectable. The tandemly arranged genes MdDAMa/MdDAMb and MdDAMc/MdDAMd were localized to chromosomes 16 and 8, respectively. Based on these observations, we infer that MdDAMa and MdDAMc acted in a dominant fashion on each locus and were correlated with the period of endodormancy.

The effects of acclimation to cold (4 °C) and heat (36/38/40 °C) on corresponding freezing and heat tolerances of one-year-old Trigonobalanus doichangensis seedlings were studied. In addition, the effects of abscisic acid (ABA) and salicylic acid (SA) pretreatments on the tolerance of this species to temperature extremes were tested. The results show that the content of soluble sugars increased with the duration of acclimation to cold (4 °C), and the relative electrical conductivity and malondialdehyde content increased significantly after 7 d; however, the content of proline did not vary significantly. After acclimation to cold for 3 and 7 d, the semilethal low temperature (LLT₅₀) was 0.8 and 1.1 °C lower, respectively, compared with that of the control. The maximum quantum yield of photosystem II (measured as variable to maximum fluorescence ratio, F_v/F_m) decreased significantly after freezing treatments (-4 to -8 °C), however, less when the plants were pretreated with 1-100 mg dm^-3 ABA. Acclimation to heat did not increase the semilethal high temperature (LHT₅₀). A low concentration (1 mg dm^-3) of SA increased LHT₅₀, but medium and high concentrations (10 and 100 mg dm^-3) decreased it. F_v/F_m decreased significantly after a heat shock (45-54 °C). The pretreatment with 1-50 mg dm^-3 SA ameliorated a subsequent heat (48 °C) stress.

Pepper (Capsicum annum L.) fruit colours vary from green, ivory, or yellow at the juvenile stage to red, orange, and yellow at the mature stage. Carotenoid accumulation causes fruit colour formation in ripe Capsicum fruits, and capsanthin is a main carotenoid in ripe red pepper fruits. In this study, pepper cultivars with red, yellow, and orange fruits were employed and four key genes named phytoene synthase (Psy), lycopene-β-cyclase (Lcyb), β-carotene hydroxylase (Crtz), and capsanthin/capsorubin synthase (Ccs) in the capsanthin biosynthetic pathway were analyzed. Results show that a clear expression of the Ccs gene in cv. CK7 (yellow) was detected, but the expressions of the Psy and Lcyb genes were low comparing with the other tested cultivars. In addition, the expression of the Ccs gene was not observed in cv. R37-1 (orange). Furthermore, though the four key genes (Psy, Lcyb, Crtz, and Ccs) were detected in red cultivar R15, the expressions of them were low. Sequence analysis further indicated that the Ccs genes in cv. CK7 and cv. R37-1 had a high sequence identity (97.36 %). Interestingly, amino acid sequences coded by the Ccs genes from cv. CK7, cv. R37-1, and cv. R15 were the same. The above results suggest that the genes Psy, Lcyb, Crtz, and Ccs were required for capsanthin synthesis in pepper, and their varied expression patterns resulted in the variety of pepper fruit colours.

The JNK motif is repeated 4 000 times in an additional heterochromatin band. Flanking sequences of a JNK region, which form extra heterochromatin in 2R rye (Secale vavilovii Grossh.) chromosomes, were studied using a genome walking technique. The results clearly indicate that there were blocks of JNK sequences adjacent to the R173 family of repeated sequences. Moreover, it appears that the R173 are sequences flanking in both directions, i.e., upstream and downstream. Downstream, the R173 is adjacent to the JNKs in an anti-parallel orientation, whereas upstream it is adjacent in a parallel orientation. In order to confirm the presence of the R173 sequence, fluorescence in situ hybridization was carried out. Using both JNK and R173 molecular probes, overlapping hybridization signals in the 2RL pair of chromosomes were observed, indicating an identical location of the two sequence elements.

Jatropha curcas L. is a perennial, drought-resistant, and non-food oilseed crop. The fatty acid composition of seed oil, especially the ratio of 16- to 18-carbon fatty acids, has a direct impact on the biodiesel quality. In plants, fatty acid chain lengths are mainly determined by the plastidial fatty acid synthase complex which includes three β-ketoacyl-acyl carrier protein synthases (KASs), KASI, KASII, and KASIII. The KASIII is thought to play a rate-limiting role in fatty acid synthesis. Here, we report the functional characterization of a putative JcKASIII gene from Jatropha curcas using Arabidopsis thaliana L. as model system. The transcripts of JcKASIII were detected in all tissues examined and increased in seeds. Overexpression of JcKASIII in Arabidopsis led to an increased content of palmitic acid and a higher ratio of 16- to 18-carbon fatty acids. Moreover, functional analysis of JcAKSIII in kasI or kasII knock down Arabidopsis mutants revealed that the composition of seed oil changed. Taken together, these results suggest that heterologous JcKASIII could function as one of the major regulators of fatty acid composition.

In plant cells, anion channels and transporters are essential for key functions. Members of the chloride channel (CLC) family located in intracellular organelles are required for anion accumulation, pH adjustment, and salt tolerance. Here, we cloned a maize (Zea mays L.) CLC gene, named ZmCLC-d, and found that its transcription was up-regulated under cold, drought, salt, and heat stresses, and after hydrogen peroxide (H₂O₂) and abscisic acid (ABA) treatments. The overexpression of ZmCLC-d in Arabidopsis conferred tolerance to cold, drought, and salt stresses; this tolerance was primarily displayed by an increased germination rate, root length, plant survival rate, antioxidant enzyme (catalase, peroxidase, and superoxide dismutase) activities, and a reduced accumulation of Cl^- in transgenic plants as compared with wild type (WT) plants. The accumulation of H₂O₂ and superoxide anion in leaves of the ZmCLC-d-overexpressing plants is much less than that of the WT plants. The expressions of some stress related genes, such as CBF1, CBF2, CBF3, DREB2A, and RCI2A, increased to a greater extent in the ZmCLC-d-overexpressing plants than in the WT. Our results strongly suggest that ZmCLC-d played an important role in stress tolerance.

We compared photosynthetic performance between cucumber (Cucumis sativus L.) leaves acclimated to saturating irradiances with high red: far red (R:FR = 10) and normal R:FR (= 1.4) ratios. The net photosynthetic rate (P_N) and stomatal conductance (g_s) of the leaves acclimated to high R:FR were greater than those of the leaves acclimated to normal R:FR; the greater g_s partly explains the greater P_N. The greater g_s of the high-R:FR-leaves probably resulted from a higher stomatal density and/or a greater size. P_N of the high R:FR leaves was still greater than that of the normal R:FR leaves at the same intercellular CO₂ concentration (c_i). This indicates that non-stomatal factors also increased the photosynthetic capacity of the high R:FR leaves. The maximum Rubisco carboxylase activity estimated from a P_N-c_i curve analysis was also greater in the high R:FR leaves, however, the intrinsic water-use efficiency (WUE_i = P_N/g_s) of the high R:FR leaves was lower than that of the normal R:FR leaves.

Roles of an altered porphyrin biosynthesis and antioxidants in protection against chilling and heat stresses were evaluated in rice (Oryza sativa L.). When exposed to the same exposure time (6 or 30 h), heat-stressed (45 °C) plants exhibited a less oxidative stress as indicated by a lower dehydration, ion leakage, and H₂O₂ production compared to chilling-stressed (4 °C) plants. Malondialdehyde production also increased after a mild chilling stress, whereas it increased only after a long-term heat stress. The content of protoporphyrin IX, Mg-protoporphyrin IX and its methyl ester, and protochlorophyllide drastically declined under both the stresses, particularly under the long-term heat stress. Greater increases in catalase and peroxidase activities in heat-stressed plants indicate more cofactors supplied for hemoproteins compared to those of chilling-stressed and untreated control plants. Intermediates of carotenoid biosynthesis, zeaxanthin and antheraxanthin, also increased under the chilling and heat stresses. In comparison to chilling-stressed plants, heat-stressed plants were more efficient in porphyrin scavenging and antioxidant enzyme responses, which may play crucial roles in plant protection under temperature stress, thereby suffering less from oxidative stress.

The secretory (Sec) pathway is one of the most important systems for transporting proteins across the thylakoid membrane into the lumen. Two Arabidopsis genes encoding SecY translocon proteins, designated SCY1 and SCY2, were characterized in this study. Semi-quantitative RT-PCR and histochemical staining β-glucuronidase (GUS) activity reveal that both SCY1 and SCY2 promoters were active in germinating seeds, etiolated cotyledons, and flowers, but not in roots. In particular, the expression of GUS gene driven by the SCY1 promoter was almost undetectable in green leaves, whereas GUS staining controlled by the SCY2 promoter was clearly detected. Moreover, homozygous scy1-1 plants could grow heterotrophically but appeared sensitive to radiation. Further studies show that chloroplasts of scy1-1 were arrested in early developmental stages with fewer thylakoid membranes. Real-time quantitative RT-PCR reveals that a number of nuclear-encoded genes involved in chlorophyll biosynthesis and photosynthesis were substantially down-regulated in the scy1-1 mutant. All these results indicate that the SCY1/2 genes were regulated developmentally and spatially, and a loss-of-function mutation in SCY1 triggered chloroplast-to-nucleus retrograde signaling in Arabidopsis thaliana.

The aim of this study was to investigate the effects of salinity on germination, seedling growth, free polyamines (putrescine, spermidine, and spermine), and ethylene metabolism of two species (Atriplex prostrata Bouchér and Plantago coronopus L.) with different salt sensitivities. Seeds collected from Barranco Hondo (salt marshes, Jaén, southern Spain) were germinated at 0, 50, 100, and 200 mM NaCl in a growth chamber. The germination of P. coronopus seeds decreased considerably with an increasing NaCl concentration, however, seeds of A. prostrata showed high germination percentages (84, 87, and 80 %) at 0 (control), 50, and 100 mM NaCl, respectively, and only at 200 mM NaCl, the germination was reduced to 25 %. In the early phase of vegetative growth (8-d-old seedlings), the fresh mass increased in A. prostrata at 50 and 100 mM NaCl but the fresh mass of P. coronopus showed no significant differences. With respect to polyamines, there was a decrease of the putrescine and spermidine content at all the NaCl treatments, however, the spermine content increased and was much higher in P. coronopus than in A. prostrata. The ethylene, 1-aminocyclopropane-1-carboxylic acid content, and the 1-amino-cyclopropane-1-carboxylic acid synthase activity increased with the increasing NaCl concentration in A. prostrata, and only the ethylene content in P. coronopus. These results indicate that P. coronopus increased the free spermine content, whereas A. prostrata increased the ethylene biosynthetic pathway in order to survive in the saline conditions.

The role of chilling in bud dormancy release and biochemical changes in different organs were evaluated in stem cuttings of pear (Pyrus pyrifolia) cv. Cuiguan selected at the leaf fall. The cuttings were exposed to 5 °C for 0, 100, 200, 300, 400, 500, 600, and 700 chilling hours (named positive chill units; PCU). A 50 % bud break was observed in floral and vegetative bud cuttings at 300 and 600 PCU, respectively. A mean time to bud break was inversely proportional to the chilling treatment. The low-temperature stimulated starch hydrolysis accompanied with sucrose accumulation in all organs. Sucrose and sorbitol content increased substantially peaking at 100, 400, and 100 PCU in floral buds, vegetative buds, and bark, respectively, thereafter decreased when buds approached chilling satisfaction (300 and 600 PCU for the floral and vegetative buds, respectively), and then increased again up to 700 PCU. Hexoses (glucose and fructose) accumulated constantly in the buds from 0 to 700 PCU. In bark, glucose and fructose content increased up to 400 PCU, and then gradually decreased. Total amylolytic and α-amylase activities increased in all organs, especially in the floral and vegetative buds up to 100 PCU and then decreased in the floral and vegetative buds before increasing again after endo-dormancy release. Invertase activity remained high in the buds during chilling satisfaction possibly because of translocation of sucrose to the buds which functioned as a strong sink. The results suggest that a low availability of hexoses may be the cause of limited bud breaks due to lack of chilling. Chilling satisfaction of the buds may increase the content of soluble sugars and acid invertase activity, and decrease the starch content, which may correlate with improved bud breaks.