Two barley (Hordeum vulgare L.) cultivars, Czech spring cv. Amulet and Syrian landrace Tadmor, were subject to different salinity treatments: 1) the NaCl concentration was gradually increased from 0 (the control) to either 100 (a moderate salt stress) or 300 mM NaCl (a high salt stress), 2) the NaCl concentration was increased directly either from 0 to 300 mM NaCl or from 100 to 300 mM NaCl, and 3) a recovery when all variants were transferred back to control conditions and cultivated for seven additional days before sampling. The following parameters were determined: water saturation deficit (WSD), osmotic potential (ψ_s), leaf proline content, maximum quantum yield of photosystem (PS) II photochemistry (measured as variable to maximum chlorophyll a fluorescence ratio, F_v/F_m), and relative accumulation of dehydrins (DHN). Both quantitative and qualitative differences in dehydrins were found between NaCl-treated Amulet and Tadmor. A principal component analysis (PCA) of all experiment data revealed a differential ability of Amulet and Tadmor to recover after the 300 mM NaCl treatments indicating better salt tolerance in Tadmor. Correlation analyses have shown statistically significant correlations between WSD, ψ_s, proline, and DHN.

Lipase class 3 is part of the triacylglycerol lipase family involved in lipid degradation, esterification, and transesterification processes in plants. In this study, a lipase class 3 gene and promoter from oil palm (Elaeis guineensis Jacq.) were isolated and characterized by Northern blot, Southern blot, oil palm genome sequence, and transient expression GUS assay. The full-length lipase class 3 (FLL1) deduced polypeptide encoded 483 amino acids and was identical to that deduced from lipase (EgLip1) cDNA (GI: 409994625). It contained the lipase consensus sequence, GxSxG motif, and a putative catalytic triad and had a 3-dimensional protein model similar to that of a lipase from Giberella zeae with a 50 % identity. The Northern blot and reverse transcription polymerase chain reaction (RT-PCR) show that FLL1 was predominantly expressed in the mesocarp and the expression increased as fruits reached maturity. A lower expression was detected in germinated seedlings and especially in roots. The expression of FLL1 was also enhanced in the mesocarp of cold treated fruits. A high oil accumulation in the mesocarp during fruit development makes this tissue a suitable target for a genetic modification, hence the isolation of the FLL1 promoter. The transient expression of the β-glucuronidase (GUS) gene driven by the FLL1 promoter detected the GUS expression in mesocarp slices, especially in vascular bundles. This suggests the potential role of using the promoter as tool to direct the expression of a transgene to the mesocarp of transgenic oil palm.

The growth of the Cd-hyperaccumulator Solanum nigrum L. and its physiological responses to a short-term (7 d) Cd stress and to exogenous methyl jasmonate (MeJA) were investigated. Compared with the leaves of S. nigrum, the roots were more liable to Cd and showed a significantly decreased dry mass and increased malondialdehyde content. Cd accumulation in the shoots and roots of S. nigrum were proportional to the Cd concentration in the hydroponic solution. The application of a low concentration of MeJA (0.01 μM) significantly reduced the translocation/accumulation of Cd in both the shoots and roots compared with a 40 mg dm^-3 Cd treatment only. Moreover, 40 mg dm^-3 Cd significantly decreased the activity of leaf superoxide dismutase, but 0.01 μM MeJA restored it. MeJA also enhanced the activity of catalase in the leaves but showed no significant effect on peroxidase activity. The content of both endogenous jasmonic acid (JA) and MeJA in the leaves of S. nigrum increased with the increase of exogenous MeJA concentration.

The GhMYB9 encodes a R2R3 MYB transcription factor in the upland cotton (Gossypium hirsutum L.) genome. Our studies show that GhMYB9 predominantly expressed in flowers and fibers. To gain a better understanding of its regulatory mechanism, we isolated the 5'-flanking region of GhMYB9 which was 1 487 bp in length. The cis-acting element prediction shows that this region contained the basic structure of the core promoter elements (TATA-box, CAAT-box) and the transcription start site (TSS). Other motifs, such as defense and stress responsiveness (TC-rich repeats), anaerobic induction (ARE), and MYB binding sites involved in drought-inducibility (MBS), were also found. Histochemical assay shows that the GhMYB9 promoter governed β-glucuronidase (GUS) expression mainly in seeds, fibers, and flowers of transgenic cotton. Also, the activity of the promoter was induced by auxin in fibers of transgenic cotton. This is consistent with its transcript abundance in different tissues. A further deletion analysis confirms that a promoter region from -1 231 to -860 was required for auxin response. Our findings provide a useful reference for the understanding of the transcriptional regulation mechanism of the GhMYB9 gene.

Actinidia kolomikta (Rupr. & Maxim.) Maxim. leaves showed dramatic colour changes during plant growth phases, and we studied structure and optical properties of variegated leaves. Leaf surface cells were smooth, and there were no surface appendages (wax or trichomes) observed in variegated leaves. Palisade tissue cells in white and pink leaves were looser and contained relatively fewer chloroplasts. White leaves contained many intercellular spaces between the epidermal and mesophyll cells or within the palisade cell layer. Variegated leaves had three distinct radiation reflection patterns: a bright white area, a spotted pattern, and a polygonal pattern. Reflectance at 450-1100 nm from the adaxial surface of white leaves was greater than that of green leaves, but anthocyanin accumulation in pink leaves decreased the reflectance at 500-600 nm. When variegated leaves turned green, the reflectance at 500-600 nm increased. On abaxial surfaces, the reflectance of variegated leaves was similar to green leaves at 450-700 nm. In conclusion, reflection patterns and the formation of variegated leaves of A. kolomikta were significantly correlated with the leaf anatomy. The white and pink colours of leaves were a result of an internal reflection between air spaces and cells in the leaves, chlorophyll deficiency in palisade tissue, and anthocyanin accumulation. Variegated leaves turned green when the chlorophyll content in palisade tissue increased.

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.

The objective of the current study was to develop an efficient and reproducible protocol for plant regeneration using nodal (1.0-1.5 cm) explants excised from a field grown mature plant of Cassia occidentalis L. The highest shoot regeneration frequency (80 %) with a maximum number of shoots (11.66) and shoot length (3.83 cm) after eight weeks of culture were observed on a Murashige and Skoog (MS) medium amended with 5.0 μM 6-benzyladenine, 100 μM citric acid, and 1.0 μM α-naphthalene acetic acid. A half-strength MS medium supplemented with 1.5 μM indole-3-butyric acid proved best for the induction of maximum roots (8.33) per shoot. Plantlets with well-developed shoots and roots were successfully acclimatized in plastic pots containing sterile Soilrite under two irradiances of 50 and 300 μmol m^-2 s^-1 (LI and HI, respectively) in a culture room, and after transfer to the field, the survival rate was 70 %. A significant increase in chlorophyll, carotenoid, and malondialdehyde content was found during acclimatization under both the irradiances but higher under HI. Similarly, the activities of superoxide dismutase, catalase, glutathione reductase, and ascorbate peroxidase increased more under HI. Plantlets acclimatized under HI exhibited a better growth than those under LI.

Hydroponics experiments were conducted to study the effects of sodium nitroprusside (SNP, a donor of NO) on lead toxicity in ryegrass (Lolium perenne L.) seedlings. When the ryegrass seedlings were grown in a nutrient solution containing 500 μM Pb²⁺ for two weeks, the plant biomass as well as net photosynthetic rate, transpiration rate, chlorophyll and carotenoid content of leaves decreased. The Pb stress also induced the production of superoxide anion (O₂ ^.-) and hydrogen peroxide (H₂O₂), leading to malondialdehyde (MDA) accumulation. Furthermore, the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) decreased in the Pb-treated seedlings, but the catalase (CAT) activity increased. Additionally, the content of Cu in shoots and the content of K, Mg, Fe, and Zn in both shoots and roots decreased, but the content of Ca in shoots and roots increased under the Pb stress. Moreover, Pb accumulated mostly in roots, whereas a small quantity was translocated to shoots. However, the addition of 50, 100, and 200 μM SNP into the solution containing Pb increased the chlorophyll content and net photosynthetic rate, reduced Pb-induced oxidative damages, improved antioxidant enzyme activities, and inhibited translocation of Pb from roots to shoots. In particular, 100 μM SNP had the best effect on promoting growth of the ryegrass seedlings under the Pb toxicity. However, the application of 400 μM SNP had no obvious alleviating effect on Pb toxicity in the ryegrass seedlings.