Nitric oxide (NO) and 5-aminolevulinic acid (5ALA) play fundamental roles in plant responses to environmental stresses, but their cross-talk in antioxidant defense in cold-stressed Elymus nutans Griseb. have not been investigated. We herein report that 5ALA and NO donor, sodium nitroprusside (SNP), alleviated cold stress-induced plant growth inhibition and lipid peroxidation in roots of two E. nutans ecotypes (Damxung, DX and Zhengdao, ZD). However, application of an NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (PTIO) differentially blocked these protective effects indicating that an inhibition of NO accumulation reduced 5ALA-enhanced cold resistance. Application of exogenous 5ALA or NO markedly up-regulated activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase, enhanced reduced glutathione accumulation and reduced glutathione to oxidized glutathione ratio, activated plasma membrane (PM) H⁺-ATPase, and reduced Na⁺/K⁺ ratio in roots of the two E. nutans ecotypes. Moreover, in the presence of 5ALA, nitric oxide synthase (NOS) activity and NO release in cold-resistant DX were higher than those in cold-sensitive ZD. Conversely, both NO treatment and inhibition of endogenous NO accumulation by PTIO or NOS inhibitor N^ω-nitro-L-arginine did not induce 5ALA production. These results suggest that NO might be acting as a downstream signal to mediate 5ALA-induced cold resistance by activating antioxidant defense and PM H⁺-ATPase and maintaining Na⁺ and K⁺ homeostasis.

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.

Screening salt-sensitive mutants is a powerful method to identify genes associated with salt tolerance. We used forward genetic screening with sodium azide-mutated rice (Oryza sativa L. cv. Tainung 67) to identify mutants showing hypersensitivity to salt stress. A new mutant line, named salt hypersensitive 1 (shs1) and exhibiting a severe salt-sensitivity when grown under a high NaCl concentration, was identified; the salt hypersensitivity was caused by duplicate recessive epistasis with mutations likely in two different loci. The shs1 salt sensitive phenotypes included a decreased seed germination rate, reduced shoot height and root length, severe and quick wilting, and overaccumulation of sodium ions in shoots as compared with wild-type plants. In addition, shs1 showed a decreased photosynthetic efficiency and enhanced hydrogen peroxide (H₂O₂) production under the salt stress. An increased superoxide dismutase activity and decreased catalase activity were responsible for the hyperaccumulation of H₂O₂ in shs1. The hypersensitivity of shs1 to the salt stress might be caused by an impaired antioxidant machinery and cellular Na⁺ homeostasis.

The amount and composition of phytohormones, sugars, and some other leaf characteristics depending on a crop load were evaluated in apple (Malus domestica Borkh. cv. Ligol grafted on P 60 rootstock) trees in order to prevent biennial bearing. The crop load was adjusted to 12 (control, unthinned), 8, 4, and 0 (non-fruiting) inflorescences (or fruits) per cm² of trunk cross-sectional area (TCSA). Inflorescences were removed in May before flowering. Phytohormones were analyzed in axillary buds and leaves in September. Results show that, in contrast to the unthinned trees, thinning to 4 fruits cm^-2(TCSA) resulted in a significant decrease of yield per tree, but a significant increase of fruit mass, return bloom, and leaf area. The heavy crop load resulted in suppressed bloom in the following year. Composition and content of phytohormones was changed considerably. Moreover, thinning resulted in an increased hexose accumulation. Such data suggest that flowering inhibition depended on the phytohormones that were exported to buds and on sugar-hormone signalling cross-talk.

Alternative respiration pathway (AP) is an important pathway which can be induced by environment stresses in plants. In the present study, we show a new mechanism involving the AP in nitrogen deprivation-induced tolerance of Poa annua callus to salt stress. The AP capacity markedly increased under a 600 mM NaCl treatment or nitrogen deprivation pretreatment and reached a maximum under the nitrogen deprivation pretreatment combined with the NaCl treatment (-N+NaCl). Malondialdehyde (MDA) and H₂O₂ content and Na⁺/K⁺ ratio significantly increased under the 600 mM NaCl treatment but less under the-N+NaCl treatment. Moreover, both the nitrogen deprivation and the NaCl stress stimulated the plasma membrane (PM) H⁺-ATPase activity and increased pyruvate content. The maximal stimulating effect was found under the-N+NaCl treatment. When the AP capacity was reduced by salicylhydroxamic acid (SHAM, an inhibitor of AP), content of MDA and H₂O₂ and Na⁺/K⁺ ratio dramatically increased, whereas PM H⁺-ATPase activity decreased. Moreover, exogenous application of pyruvate produced a similar effect as the nitrogen deprivation pretreatment. The effects of SHAM on the Poa annua callus were counteracted by catalase (a H₂O₂ scavenger) and diphenylene iodonium (a plasma membrane NADPH oxidase inhibitor). Taken together, our results suggest that the nitrogen deprivation enhanced the capacity of AP by increasing pyruvate content, which in turn prevented the Poa annua callus from salt-induced oxidative damages and Na⁺ over-uptake.

Jasmonate ZIM domain (JAZ) proteins are key regulators of the jasmonic acid (JA) signaling pathway. Repressors of JAZ remain bound to the myelocytomatosis 2 (MYC2) or MYC3/MYC4 transcription factors in the absence of JA and negatively regulate transcription of the JA responsive genes. In the presence of JA, JAZ proteins interact with coronative insensitive 1 (COI1), the recognition molecule of E3 ubiquitin ligase SCF^COI1 (COI1 stabilized by Skp, cullin, F-box containing complex), get ubiquitinated, and subsequently degraded by the 26S proteasome. However, there is a dearth of knowledge about this gene family in monocot cereals, specifically its role in finger millet is unknown till date. Here we present the isolation and characterization of a novel JAZ family repressor gene from nonsequenced Eleusine coracana (EcJAZ) utilizing available genome information of Oryza, Sorghum, and Setaria. The EcJAZ sequence showed the presence of a conserved ZIM domain, the Jas motif, and N-terminal motif 7 like other Group1 TIFY sequence containing proteins. We observed coronatine (an analog of JA-Ile) dependent and time dependent degradation of recombinant EcJAZ that thereby fulfilled the basic characteristic of the JAZ proteins. We found a proteasome inhibitor N-(phenylmethoxy) carbonyl-L-leucyl-N-[(1R)-1-formyl-3-methylbutyl]-L-leucinamide) (MG132) mediated degradation inhibition of EcJAZ that supported its 26S proteasome mediated degradation. Our study shows the nuclear localization of GFP-EcJAZ by Agrobacterium mediated transient transformation of onion scale epidermal cells. In Eleusine leaves, transcription of EcJAZ increased 4.2-fold by salt stress and 5.5-fold by coronatine application; thus ascertained its inducibility by the abiotic stress as well as by bioactive JA-Ile. Taken together, all these results contribute to our understanding of the JA signaling pathway in Eleusine coracana.

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.

Pogostemon cablin (Blanco) Benth is a medicinal plant rich in terpenoids and flavonoids. Currently, the molecular mechanism of flavonoid biosynthesis in P. cablin remains unclear. In this study, three copies of the phenylalanine ammonia lyase (PAL) gene designated as PcPAL1 - PcPAL3, one copy of the chalcone synthase (CHS) gene referred to as PcCHS, and four copies of the CHS-like gene referred to as PcCHSL1 - PcCHSL4 were isolated from P. cablin. PcPAL1, PcPAL2, and PcPAL3 comprised 2 136, 2 136, and 2 148 bp full-length open reading frames (ORFs) encoding 711, 711, and 715 amino acids, respectively. PcCHS, PcCHSL1, PcCHSL2, PcCHSL3, and PcCHSL4 contained 1 173, 1 176, 1 179, 1 173, and 1 170 bp ORFs encoding 390, 391, 392, 390, and 389 amino acids, respectively. A phylogenetic analysis indicates that PcPAL2 was closer to PcPAL3 than PcPAL1, and that PcCHS was clustered with other plant CHS genes but independently to the PcCHSLs subgroup. A sequence analysis shows that PcCHSLs diverged in functional residues when compared to plant CHSs including PcCHS, suggesting that PcCHSLs may be divergent in tertiary structures. A quantitative reverse-transcription polymerase chain reaction analysis indicates that the expression profiles of PcPALs, PcCHS, and PcCHSLs in leaves and stems differed among four cultivars. Our results suggest that divergence in sequence and expression profiles of the tested genes may contribute to the diversity in flavonoids among the four cultivars.

We previously reported that LeMYB1 might be a crucial transcription factor in regulating shikonin formation in Lithospermum erythrorhizon. In this study, by overexpressing LeMYB1 under the control of CaMV35S promoter in L. erythrorhizon hairy roots, we further clarified the role of LeMYB1 in the shikonin formation and its regulation. The LeMYB1-overexpressing transgenic hairy roots were successfully induced by infecting seedling nodes with Agrobacterium rhizogenes strain ATCC15834 that carried the pBI121-LeMYB1 vector. The LeMYB1 transcripts were significantly up-regulated in the transgenic hairy root lines compared with the wild type lines, and the total content of shikonin and its derivatives was dramatically enhanced by the LeMYB1 overexpression. Real-time PCR results reveal that the enhanced shikonin biosynthesis in the overexpressing lines were mainly caused by a highly up-regulated expression of genes coding key enzymes (PAL, HMGR, and PGT) and key regulators (LeDI-2 and LePS-2) involved in the shikonin biosynthesis. Overall, our results suggest that LeMYB1 plays a positive role in regulating the shikonin biosynthesis in L. erythrorhizon.

Whereas microsatellite markers are well described, there are few studies investigating minisatellites. Therefore, this study aimed to identify, characterize, and validate minisatellite loci for papaya (Carica papaya L.). The entire papaya genome, which covers 330 Mb, was used to mine minisatellites with motifs ranging from 6 to 500 bp, and at least six replicates and 82 loci were validated in a set of 24 accessions. A total of 1 730 minisatellite loci were identified, located in 695 sequences, with an average of one minisatellite every 156 kb. Variation in GC content ranged from 0.00 to 83.84 % with an average of 28.84 % indicating that these papaya minisatellites are AT rich. Motifs of up to 20 bases represented 71.45 % of the markers. In addition, the observed variation in the number of motif repeats was from 6 to 186 with an average of 9.27 per minisatellite. Independent of the classification, the frequency of minisatellites decreased with an increase in the number of repeating units. Among the validated loci, 48.78 % were found to be polymorphic, and the number of alleles (N_A) ranged from two to seven with a mean of 3.10. The average polymorphic information content (PIC), expected heterozygosity (He), and observed heterozygosity (Ho) were 0.38, 0.43, and 0.11, respectively. According to genetic diversity parameters, such as NA, He, and PIC, no significant correlations were found among the size of motifs, the number of repeats, and the GC content of these minisatellites. This study clearly demonstrates the polymorphism of minisatellites and their potential use in detection of intraspecific genetic variations in C. papaya. The results will be useful when managing genetic resources and plant breeding.

Natural accessions of Arabidopsis thaliana exhibit a clinal variation in freezing tolerance following temperature changes across the natural habitat. Here we performed molecular evolution and population genetic analyses of homologous INDUCER OF CBF EXPRESSION1 (ICE1) and ICE2 genes, the master regulators of plant cold response. A study of ICE genes polymorphism was performed using 60 A. thaliana ecotypes grouped according to their geographic origin. The genetic diversity of ICE2 was characterized by a high number of haplotypes and an overall high diversity. The levels of nonsynonymous nucleotide polymorphism increased from a northern group southward. On the contrary, the ICE1 gene sequence was less diverse and there was no clinal variation in the sequence polymorphism. Thus, different selection forces acting on the ICE2 gene might be one of the reasons of clinal variation in freezing tolerance. This clinal variation also indicates that ICE2 is more important for a cold response than ICE1. The study of the ratio of numbers of nonsynonymous to synonymous substitutions (K_a/K_s) between A. thaliana paralogs shows that the sequence diversification and emergence of two new ICE2-specific motifs could contribute to the functional diversification of the duplicates. The K_a/K_s for ICE2 of A. thaliana and A. lyrata orthologs was an order of magnitude greater than that for the ICE1 orthologs, which suggests that the protein sequence of ICE2, an early duplicate, evolved under a weaker selective constraint. A relaxed selection on ICE2 in southern populations and more stringent in northern populations also confirmed its role in a cold resistance. The selection pressure on ICE1 might be caused by its role in the control of more essential than cold response functions.

Understanding the basis of the genetic variations responsible for the complex traits found in Eucalyptus cladocalyx under arid environmental conditions is crucial for designing genetic architecture studies. Forty-five half-sib families from Australia were used to identify inter-simple sequence repeat (ISSR) markers that are associated with growth (height, diameter at breast height, and stem straightness), flowering traits (flowering intensity, flowering precocity, reproductive capacity, and late flowering) and tree survival under arid conditions in southern Atacama Desert, Chile. Each DNA pellet consisted of a pool of five trees from each family. ISSR markers were associated with all the traits studied and accounted for 9.8 to 23.4 % of the phenotypic variation. Several loci were associated with more than one trait. For example, UBC_{810(450-500 bp)}, ISO_{1(600-610 bp)}, and TGT_{9(780-800 bp)} were associated with three of the traits studied. These identified genomic regions may contribute to the increase of the efficiency of the conventional tree breeding program for E. cladocalyx.

The present work examined seven Hypericum species (H. perforatum, H. humifusum, H. kalmianum, H. annulatum, H. tomentosum, H. pulchrum, and H. rumeliacum) produced in vitro and regenerated after cryopreservation. The aim of the study was to assess, by means of light microscopy (LM) and transmission electron microscopy (TEM), the effect of freezing temperature on leaf histological organization and mesophyll chloroplast ultrastructure. Histological analysis showed a negative effect of ultralow temperatures on leaf tissue structure in H. pulchrum and a positive effect in H. perforatum. The TEM analysis showed that chloroplasts from ultralow temperature treated H. annulatum, H. tomentosum, and H. rumeliacum had a typically structured internal membrane system without destruction of thylakoid membranes, however, those of H. humifusum had very high grana, and in H. perforatum, chloroplast thylakoid destruction occurred. The chloroplast internal membrane system of in vitro cultured control plants and in vitro cultured cryopreserved plants of H. kalmianum and H. pulchrum had a specific spatial orientation without any destruction of the membranes. The results show a specific response of each species to these experimental conditions.

To study the effects of application of salicylic acid (SA) on the antioxidant system and photosystem II (PS II) in wheat seedlings we used two different experiments. The first method was carried out by immersing roots in Hoagland's nutrient solution containing 0, 0.25, or 2.5 mM SA, and the second method was performed by spraying two-week-old seedlings with the same SA concentrations. After 24 h, chlorophyll fluorescence, thylakoid membrane proteins, antioxidant enzyme activities, and reactive oxygen species were measured. The low concentration of SA caused a significant increase in the antioxidant enzyme activities. However, the treatment with 2.5 mM SA resulted in an increase in the non-photochemical quenching coefficient and a decrease in the antioxidant enzyme activities, the quantum yield of PS II photochemistry, and the photochemical quenching, especially in the first method of application. All these results indicate that the effects of SA on PS II and the antioxidative defense system were dependent on the concentration used and the method of application.

Agricultural production worldwide has been severely impacted by cold and freezing stresses. Plant capacity to acclimate to environmental conditions in their immediate vicinity largely control their survival, growth, and productivity. Molecular as well as biochemical mechanisms underpinning plant cold acclimation are very complex and interwoven. The cold-impacted plants try to modulate expression of variety genes controlling cell membrane lipid composition, mitogen-activated protein kinase cascade, total soluble proteins, polyamines, glycinebetaine, proline, reactive oxygen species (ROS) scavengers, cryoprotectants, and a large number of cold responsive factors. To this end, this paper dissects the array of transcriptional factors/genes down- or up-regulated, their identification in different plant species, recognition of cold tolerant/resistant transgenic plants, complexity of the mitogen-activated protein kinase cascade, as well as their cross talk under different stresses and molecular mechanisms. Furthermore, it also comprehensively elucidates physio-biochemical interferences in cold acclimation with a particular emphasis on endogenous content as well as exogenously supplied different types of polyamines, ROS, and osmoprotectants. Overall, low temperature stress tolerance or cold acclimation varies greatly among species depending on the stress intensity and duration and type of plant species.

A new member of the APETALA2/ethylene responsive element binding protein (AP2/EREBP) transcription factor family, HhDREB2, was isolated from Halimodendron halodendron. Based on the similarity of the AP2/ERF domain, HhDREB2 was classified into A-5 group of the DREB subfamily. The expression of HhDREB2 gene was induced by drought, high salinity, and low temperature, but not by exogenous plant hormones. Trans-activity assay demonstrated that HhDREB2 gene encodes a transcription activator. Furthermore, over-expression of HhDREB2 gene under the stress-inducible rd29A promotor in Arabidopsis resulted in enhanced tolerance to salt and drought stresses. The overall results reveal that HhDREB2 functioned as important transcription factor in regulation of stress-responsive signaling in plants and may be used for improving plant tolerance to abiotic stresses.

The effects of AT3-gene silencing on the expression of genes involved in capsaicinoid biosynthesis was investigated in chili pepper (Capsicum annuum L.) cv. Tampiqueño 74 fruits. Seeds were germinated and seedlings were grown in a greenhouse until they produced fruits. Capsaicinoids (capsaicin and dihydrocapsaicin) content and AT3 gene expression were determined in placenta tissue from fruits at 10, 20, 30, 40, 50, and 60 days post-anthesis (DPA). Capsaicin was more abundant than dihydrocapsaicin and both exhibited a similar accumulation pattern at different developmental stages starting at 20 DPA, reaching maximum values at 30-40 DPA before decreasing. The AT3 gene expression, as measured by quantitative RT-PCR, was positively correlated with capsaicinoid accumulation; AT3 transcripts were detected at 20 DPA, achieved a maximum at 30-40 DPA and then decreased. The Tampiqueño 74 seedlings were infected with Agrobacterium tumefaciens bearing a pTRV2-AT3 construct to induce virus-mediated silencing. Fruits were harvested at 40 DPA, and capsaicinoid content and AT3 gene expression were carried out in placenta tissue. A reduction of 81.1 % in AT3 expression and also in capsaicin (89.6 %) and dihydrocapsaicin (87.7 %) content was recorded in the AT3-gene silenced chili pepper plants. Furthermore, fruits from the AT3-silenced plants compared to the non-infected control plants showed a statistically significant reduction in the expression of genes involved in capsaicinoid biosynthesis [pAmt (89.4 %), BCAT (68.8 %), Kas (90.4 %) and Acl (58.6 %)]. These data indicate that AT3 silencing had a negative effect on the transcription of genes involved mainly in the branched-chain fatty acid pathway of capsaicinoid biosynthesis.

An excess of aluminum (Al) is a major factor limiting crop production in acidic soils. Secretion of organic acids (OAs) from the root apex of diverse plant species or genotypes via activation of anion channels has been recognized as the most important mechanism of Al exclusion. Citric, oxalic, and malic acids are the most effective OAs in detoxifying Al. In this review, we summarize biochemical properties of OAs secreted by plants. We also highlight the molecular mechanisms of Al signal perception, Al transport, signal regulators associated with OAs secretion, as well as interactions between Al and hormone signaling pathways. Based on a comprehensive understanding of the relationship between signal modulators and regulation of expression of relevant genes, a signal transduction model for Al-induced OAs secretion is proposed.

The interactive effects of salicylic acid (SA) and nitric oxide (NO) on alleviating cadmium (Cd) toxicity in peanut (Arachis hypogaea L.) were studied. Seedlings of two cultivars (Huayu 22 - a big seed type, and Xiaobaisha - a small seed type) were treated with 200 μM CdCl₂ without or with 0.1 mM SA or 0.25 mM sodium nitroprusside (SNP, an NO donor). Results show that the Cd exposure depressed the plant growth of both the cultivars but more of Huayu 22 than of Xiaobaisha. Exogenous SA and NO alleviated Cd toxicity in both the peanut cultivars: they improved growth, chlorophyll content, photosynthesis, and mineral nutrition. Furthermore, exogenous SA or NO decreased oxidative stress by increasing activities of antioxidant enzymes and content of non-enzymatic antioxidants. Besides, in roots and leaves of both the cultivars, exogenous SA and NO increased Cd accumulation in the cell wall and decreased Cd distribution to organelles. In particular, the effect of SA+SNP was most obvious.

Previously, the ascorbate peroxidase (APX1) activity and gene expression in Chinese cabbage (Brassica campestris, Bc) heat-tolerant cv. ASVEG2 were found to be significantly higher than in heat-sensitive cv. RN720 under a heat stress. Furthermore, BcAPX2 and BcAPX3, isoforms of BcAPX1, were cloned in this study. Our objective was to transfer BcAPX cDNA under the control of the ubiquitin promoter to Arabidopsis via Agrobacterium tumefaciens strain GV3101. We found that BcAPX genes were overexpressed in transgenic Arabidopsis, and the expression of APX, and the APX activity in transgenic lines were higher than in non-transgenic (NT) plants under high temperatures. The chlorophyll content and the germination rate were significantly higher, and the malondialdehyde content was lower in BcAPX1-3, 2-1, and 3-5 lines subjected to the heat-stress treatment than those in the NT plants. Compared to the NT plants, a lower heat-induced H₂O₂ accumulation was detected by diaminobenzidine staining in leaves of the transgenic lines with a high APX activity indicating that the overexpression of BcAPX in Arabidopsis could enhance heat tolerance by eliminating H₂O₂.

Little is known about Ni storage in seeds of hyperaccumulating plants and its possible role in the first stages of plant development. The aim of this study was to determine Ni distribution in seeds and seedlings during germination and to test its role during germination with and without an external Ni supply. Field-harvested seeds from the South African Ni-hyperaccumulator Berkheya coddii Roessler were germinated either in Ni-free deionised water or in ultramafic soil. Sections of seeds and seedlings were analyzed using micro-proton induced X-ray emission (micro-PIXE) in order to localise Ni and other elements. Results show that high amounts of Ni were stored within the seeds. In germinating seeds, Ni was located in different parts: the lower epidermis, margins of cotyledons, and the pericarp in the micropylar area. The Ni and Ca were not mobilised during germination sensu stricto. Emergence of the first leaf seemed to trigger the translocation of Ni and Ca within the seedling. Besides, no effect of Ni supply from soil on its redistribution could be established for the germination stage.

In order to reveal the character of ammonia emission in senescent tobacco (Nicotiana tabacum), the content of NH₄ ⁺, total nitrogen, and soluble protein, and the activities of nitrogen metabolism-related enzymes were measured in leaves of a quick-leaf-senescence phenotype ZY90 and a slow-leaf-senescence phenotype NC89. Compared with NC89, ZY90 had a higher NH₄ ⁺ accumulation, a lower glutamine synthetase activity, and a significantly higher stomatal ammonia compensation point, and ammonia emission during 40 to 60 d after leaf emergence. During senescence, the quick-leafsenescence phenotype was characterized by nitrogen re-transfer by ammonia emmission, whereas the slow-leafsenescence phenotype by nitrogen re-assimilation. The ammonia emission was primarily regulated by glutamine synthetase activity, apoplastic pH, and NH₄ ⁺ content.

The effects of a long-term simulated spring-summer UV-B daily course on some anatomical, physiological, and biochemical features were studied in new and old leaves of blueberry (Vaccinium corymbosum L.) cultivars Legacy, Brigitta, and Bluegold. The results show that under UV-B exposure, leaf thickness increased in Bluegold due to an increased intercellular cavities. By contrast, Brigitta maintained its leaf thickness. The net photosynthetic rate was not significantly affected by the UV-B radiation in any of the cultivars; however, Brigitta presented a better photosystem II performance, since this cultivar had more efficient photochemistry under the UV-B radiation. In addition, Brigitta also maintained enhanced total phenol and total anthocyanin content compared to the other cultivars. In conclusion, Brigitta was more resistant to the UV-B radiation than the other two cultivars.

Ascorbate (AsA) is an important antioxidant that can scavenge reactive oxygen species to protect plant cells against oxidative stress. Guanosine 5'-diphosphate (GDP)-L-galactose phosphorylase (GGP) is a key enzyme in the AsA biosynthetic pathway. To investigate the functions of GGP in AsA synthesis and oxidative stress tolerance in tomato, antisense lines with a reduced expression of SlGGP were obtained. Photobleaching after treatment of leaf disks with methyl viologen was more severe in transgenic lines compared to wild type (WT) plants. Moreover, compared with the WT plants, the transgenic plants showed a higher content of hydrogen peroxide, superoxide anion, malondialdehyde, as well as ion leakage, but a lower content of AsA and chlorophylls, ascorbate peroxidase activity, net photosynthetic rate, and maximal photochemical efficiency of photosystem II. Results of real-time quantitative polymerase chain reaction show that suppression of the SlGGP gene in the transgenic plants reduced their oxidative stress tolerance.

To elucidate a physiological mechanism of heat stress mitigation by exogenous glucose, seedlings of Cucumis sativus cv. Jinchun No. 4 were pretreated with glucose and then exposed to normal (25/18 °C) and elevated (42/38 °C) temperatures. We investigated whether glucose can protect cucumber plantlets and chloroplast ultrastructure from heat and whether this protection is associated with antioxidant enzymes, proline, and soluble sugars. Heat inhibited plant growth, disorganized membranes of 86.33 % of chloroplasts, and elevated the content of malondialdehyde (MDA), superoxide radical (O₂ ^.-), and hydrogen peroxide (H₂O₂). An optimum concentration of glucose was 30 mM as it significantly alleviated plant growth inhibition and obviously reduced the content of MDA, O₂ ^.-, and H₂O₂ under the heat stress. The pretreatment with 30 mM glucose mitigated heat-induced damage of chloroplast ultrastructure and changes in leaf morphology more than 30 mM mannitol suggesting that glucose did not act only as osmolyte. Moreover, the glucose pretreatment increased activities of some antioxidant enzymes and enhanced the content of proline and soluble sugars under the heat stress, as well as the transcriptions of Cu/Zn-superoxide dismutase, Mn-superoxide dismutase, catalase, and glutathione reductase genes. We conclude that the pretreatment with 30 mM glucose protected chloroplast ultrastructure and enhanced heat tolerance of the seedlings by the increased activites of antioxidants and the content of proline and soluble sugars, and repressed accumulation of reactive oxygen species.

The dehydration responsive element binding (DREB) transcription factor (TF) family comprises unique and important proteins involved in abiotic stress responses and tolerance in plants. Although DREB TFs have been well identified and characterized in a few model plants, there is no detailed information available for mulberry. In this study, 110 AP2/ERF family genes were identified based on a genome-wide analysis of the Morus genome database. Among them, 30 Morus notabilis DREB family genes (MnDREBs) were identified. A comparative analysis with DREB gene families from other plants suggests that MnDREBs could be divided into six subgroups (A-1 to A-6) and could have similar functions in response to abiotic stresses since they have similar conserved domains/motifs within each subgroup. The expression patterns of MnDREBs were analyzed using transcriptome data of different organs from M. notabilis and the quantitative real-time polymerase chain reaction. The expression of most MnDREBs was detected in different organs and induced by various abiotic stresses, which suggest their vital roles in abiotic stress tolerance.

We investigated the effect of sulfur (S) supply on growth, oxidative stress, and iron uptake and transport in rice (Oryza sativa L.) seedlings using a hydroponic culture with four S concentrations (0, 1.75, 3.5, and 7.0 mM). The length and fresh mass of seedlings were enhanced with the increased S concentration. In addition, the content of thiobarbituric acid reactive substances (TBARS) in rice leaves was the highest when no S was added to the nutrition solution and gradually declined with the increasing S supply. The higher S nutrition reduced the amount of Fe plaque on rice roots and increased Fe content in roots and leaves. The content of nicotianamine was significantly higher in rice roots under the S deficiency, whereas the reverse trend was observed in rice shoots. Taken together, the sufficient S nutrition promoted growth of rice, reduced oxidative stress, and ensured normal Fe uptake and distribution.

The effects of chilling (CT, day/night temperatures of 12/10 °C, an irradiance of 250 μmol m^-2 s^-1), chilling combined with a low irradiance (CL, 12/10 °C, 80 μmol m^-2 s^-1), and a high temperature (HT, 42/40 °C, 250 μmol m^-2 s^-1) on chlorophyll content, chlorophyll fluorescence, and gas exchange were studied in two watermelon cultivars, ZJ8424 and YS01, differing in their resistance. The chlorophyll content, net photosynthetic rate (P_N), stomatal conductance (g_s), and transpiration rate (E) decreased substantially, whereas the intercellular CO₂ concentration (c_i) increased when the two watermelon cultivars were grown under these stresses. The photosynthetic parameters showed greater changes at chilling than at the high temperature, and the CL caused a more pronounced inhibition in PN compared with the CT. After 2 d exposure to the CT, YS01 had higher P_N, g_s, and E, but a lower ci compared with ZJ8424. The maximum efficiency of photosystem (PS) II photochemistry (F_v/F_m), effective quantum yield of PS II photochemistry (Φ_PSII), photochemical quenching (qP), and electron transport rate (ETR) decreased under the CT and CL but showed only a slight drop under the HT. All these stresses significantly increased non-photochemical quenching (NPQ). The CT brought more damage to the photosynthetic apparatus of leaves compared with the CL. In addition, after returning to normal conditions (25/15 °C, 250 μmol m^-2 s^-1) for 3 d, the photosynthetic parameters recovered to pre-stress levels in HT treated seedlings but not in CT treated seedlings. In conclusion, the low irradiance could help to alleviate the extent of photoinhibition of PS II photochemistry caused by chilling and cv. ZJ8424 was more sensitive to the extreme temperatures than cv. YS01.

Phenylalanine ammonia lyase (PAL) is the first enzyme in the phenylpropanoid pathway. In this study, we describe the molecular characteristics of four PAL genes (MaPAL1, MaPAL2, MaPAL3, and MaPAL4) cloned from banana (Musa acuminata L. AAA group, cv. Cavendish) using a rapid amplification of cDNA ends and real time quantitative PCR. The predicted molecular masses of corresponding PALs ranged from 70.2 to 77.3 kDa and their isoelectric points were acidic. At the amino acid level, they shared a high sequence similarity with PALs in the banana DH-Pahang (AA group) genome. Phylogenetic analysis shows that the deduced amino acid sequences of MaPALs had also a high similarity with PALs of other plant species. Expression analysis by semi-quantitative reverse transcriptase PCR reveals that these genes were differentially expressed in various tissues. Enzyme activity of PAL and expression of MaPALs in bananas were induced after infection with Fusarium oxysporum f. sp cubense Tropical Race 4. Our findings suggest that MaPALs play important roles in banana resistance to F. oxysporum.