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.

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.

Low expression of osmotically responsive genes 2 (LOS2) encodes an enolase (2-phospho-D-glycerate hydrolase, EC 4.2.1.11) that converts 2-phospho-D-glycerate (PGA) to phosphoenolpyruvate (PEP) in the glycolytic pathway in Arabidopsis. Meanwhile, it is a transcriptional activator of cold-responsive gene, negatively controlling the expression of STZ/ZAT10, a zinc finger transcriptional repressor of cold-responsive gene from Arabidopsis. A novel LOS2 gene, designated PtrLOS2 (GenBank accession number GQ144341), was isolated from trifoliate orange [Poncirus trifoliata (L.) Raf.]. The PtrLOS2 cDNA is 1 662 bp in length with a 1 338 bp open reading frame (ORF), encoding a deduced 445 amino acid residue protein with a predicted molecular mass of 47.79 kDa and an isoelectric point of 5.54. The deduced protein of the PtrLOS2 gene shares high identity (over 86 %) with other plant species enolase, which suggests that the PtrLOS2 probably encodes an enolase. Sequence alignment showed that PtrLOS2 protein has a conserved DNA-binding and a repression domain. Moreover, a conserved start site of alternative translation for the c-myc promoter binding protein (MBP-1) was also found in PtrLOS2 protein. PtrLOS2 was constitutively expressed in leaves, stems and roots. PtrLOS2 expression in roots and stems was much higher than that in leaves under normal conditions, however, the expression of PtrLOS2 was up-regulated in leaves, but down-regulated in roots after cold treatments. The PtrLOS2 expression in stems was firstly up-regulated and then down-regulated after cold treatments. Meanwhile, after ABA treatment, the expression of PtrLOS2 was up-regulated in leaves but in stems and roots firstly down-regulated followed with up-regulation.

Candidate Arabidopsis thaliana S-domain receptor-like kinase (SD-RLK) (At1g11330, At1g61430, and At1g61610) and leucine-rich repeat receptor-like kinase (LRR-RLK) (At1g51850, At2g19190, and At5g45840) genes were characterized utilizing PlantPAN, AGRIS, and AthaMap databases. Following determination of the main conserved domains, both classes of RLKs were found to be structurally similar with extracellular, transmembrane, and intracellular domains including a serine/threonine kinase domain, which might suggest a functional role in intracellular signal transduction. This established that the RLK genes had a superficially similar structure but distinct ligand binding domains. The expressions of these genes in response to a treatment with microbe-associated molecular pattern molecules (MAMPs), namely lipopolysaccharides, flg22 peptide from flagellin, peptidoglycan, chitosan, and ergosterol were compared. The candidate RLKs, potentially involved in surveillance, were found to be responsive to the elicitation treatments. Furthermore, differential regulation that was observed at the transcriptional level as well as the intensity of responses could possibly be correlated to the promoter architecture. With the use of in silico analyses, the architectures of 1 000 bp promoter regions upstream from the transcription start sites were determined. The analyses also revealed putative defense-related cis-regulatory elements that included W-boxes, MYB factor, AP2/ERF-, GT1- and ATHB-5 binding sites. The frequency at which these cis-elements occurred in each promoter differed, and the number or clusters within the core-regulatory region of individual promoters might be indicative of the responsiveness of each gene to the MAMP elicitation.

C-repeat binding factor (CBF), also called the dehydration-responsive element binding factor 1 (DREB1), can be induced by low-temperature (LT), and plays an important role in abiotic stress tolerance in higher plants. In present study, two new homologous genes of CBF from Prunus mume (PmCBFb and PmCBFc) have been identified and characterized. The complete coding sequences of PmCBFb and PmCBFc were 714 and 723 bp, respectively. They encoded putative proteins of 237 and 240 amino acids. Neither of them had introns. Genome PCR sequencing showed that PmCBFb was arranged in tandem with PmCBFa (another CBF/DREB1 homolog in P. mume) within a region of nearly 4 kb. Promoter prediction analyses indicated that multiple types of cis-elements related to abiotic stress and irradiance existed in the putative promoter region of PmCBFb. LT treatment of seedlings showed that the expression of PmCBF genes were induced by 2 °C within 30 min, and their expression reached a peak after 8-12 h. In addition, PmCBFa and PmCBFb appeared more sensitive to LT than PmCBFc. However, the exact roles of PmCBF genes in plant cold tolerance need to be further investigated.

Plant glutathione peroxidases (GPX) catalyze the reduction of H₂O₂ or organic hydroperoxides to water, mitigating the toxicity of these compounds to cells. In rice plants, the GPX gene family is composed of five members that are distributed in a range of sub-cellular compartments including cytosol, mitochondria, chloroplasts, or endoplasmic reticulum. Of these, OsGPX1 and OsGPX4 are located in mitochondria and chloroplasts, respectively. To understand the role of these GPX in rice, the effect of knockdown of OsGPX1 and OsGPX4 in rice plants was evaluated. Our data show that OsGPX4 was essential for in vitro rice regeneration because no plants were obtained from calli carrying a hairpin construct against OsGPX4. Although the knockdown of OsGPX1 did not impair plant regeneration, the plants with silenced OsGPX1 (GPX1s plants) showed reduced shoot length and a reduced number of seeds compared to the non-transformed rice plants. These results indicate that OsGPX1 and OsGPX4 are essential for redox homeostasis which leads to normal growth and development of rice.

The issue of finding plants suitable for phytoremediation of inorganic contaminants can be addressed through the preparation of genetically modified plants with an increased metal accumulation potential. A HisCUP gene, which encodes for a yeast metallothionein fused with a polyhistidine tail (His), was chosen for preparation of two plant vectors. These two plant vectors were constructed and a HisCUP gene expression was subsequently investigated. We firstly prepared a vector pNOV2819/RbcS/HisCUP which enabled selection on a mannose medium and contained the HisCUP gene under an inducible Rubisco promoter. Secondly, we designed a vector pGreen0029/35S/HisCUP which enabled selection of plants on a medium with kanamycin and carried the HisCUP gene under a constitutive CaMV 35S promoter. The transient expression of the HisCUP gene in tobacco plants was confirmed at RNA and protein levels for both constructs. The relative expression of the HisCUP gene was determined by semi-quantitative real-time PCR; a higher expression was detected for the vector pNOV2819/RbcS/HisCUP.

Growth, photosynthetic characteristics, chlorophyll (Chl) fluorescence parameters, and peroxidation of membrane lipids of Cryptotaenia japonica were studied under differing irradiances (15, 35, 60, and 100 % of full irradiance). At full irradiance, C. japonica exhibited a typical decline in net photosynthetic rate (P_N) at midday, which was not observed in the other irradiance treatments. This indicates a possible photoinhibition for C. japonica at the high irradiance. Diurnal patterns of stomatal conductance (g_s) were remarkably similar to those of P_N in each irradiance treatment, and the intercellular CO₂ concentration (c_i) had the opposite trend. C. japonica growing under 60 % of the full irradiance exhibited the highest plant height, stem diameter, leaf area, and biomass. The initial fluorescence (F₀) value was lowest at 60 % of the full irradiance. Maximal fluorescence (F_m), potential activity of photosystem II (PS II) (F_v/F₀), and maximal photochemical efficiency of PS II (F_v/F_m) values were highest at 60 % of full irradiance and lowest at 15 % of the full irradiance. The malondialdehyde (MDA) content in 15 % and 100 % of the full irradiance were higher than under the other irradiances. During the treatment, catalase, peroxidase, and superoxide dismutase activities firstly increased and then declined under 15 % and 100 % of the full irradiance and were steadily low under 60 % of the full irradiance, indicating a low production of reactive oxygen species. Therefore, C. japonica thrived best under 60 % of the full irradiance.

Iron deficiency chlorosis occurs frequently in calcareous soils. The transformation of plants with ferric chelate reductase genes (FROs) provides a potential strategy to alleviate plant chlorosis under iron deficiency. A CjFRO2 gene isolated from Citrus junos Sieb. ex Tanaka was introduced into Poncirus trifoliata (L.) Raf via Agrobacterium-mediated transformation. The transgene integration and expression were confirmed by PCR, Southern blot, and real-time PCR analyses. Hydroponic- and soil-grown transgenic plants were tested for their tolerance to iron deficiency. Compared with nontransgenic (NT) P. trifoliata plants, a rhizosphere acidification capacity in the transgenic lines increased, and a ferric chelate reductase activity in roots was up to 3.39- and 2.93-fold higher in a hydroponic solution and soil, respectively. A transgenic line TO-8, which reacted similarly in hydroponics and soil, appeared tolerant to the iron deficiency. Its leaf chlorophyll and ferrous ion content was significantly higher than in NT. These results indicate that tolerance to the iron deficiency in P. trifoliata could be improved through the genetic engineering.

In chloroplasts and mitochondria, antioxidant mechanisms include the ascorbate-glutathione cycle, and monodehydroascorbate reductase (MDHAR) is important for regeneration of ascorbate (AsA) from monodehydroascorbate (MDHA). To improve detoxification of reactive oxygen species (ROS), we established a construct of the MDHAR gene from Brassica rapa fused to the targeting signal peptides of Pisum sativum glutathione reductase (GR), which was controlled by a stress-inducible SWPA2 promoter, and introduced this expression system into Arabidopsis thaliana. Transgenic (TG) plants overexpressing BrMDHAR targeted to chloroplasts and mitochondria through signal peptides showed an elevated MDHAR activity and an increased ratio of AsA to dehydroascorbate (DHA) when compared to wild-type (WT) plants under a freezing stress. These led to increased photosynthetic parameters, redox homeostasis, and biomass in TG plants when compared to the WT plants. Our results suggest that the overexpression of the BrMDHAR gene targeted to chloroplasts and mitochondria conferred an enhanced tolerance against the freezing stress, and a stress adaptation of dual-targeted BrMDHAR was better than that of single BrMDHAR.

Low temperature is the main limiting factor for cultivation expansion, fast growth, and high yield of Eucalyptus species. To investigate the mechanism of their cold tolerance, a cDNA subtraction library representing the cold-induced genes of Eucalyptus dunnii was constructed using suppression subtractive hybridization (SSH) technique. A gene encoding a calmodulin-binding protein (CaMBP) was identified from the SSH library, and the expression pattern of CaMBP under cold stress was further evaluated through reverse transcription - quantitative polymerase chain reaction (RT-qPCR). The expressions of EguCBF1a and EdCaMBP increased already after 4 h of the cold stress, supporting the idea that the CaMBP gene may have a function in the survival of Eucalyptus during winter. A full-length mRNA sequence of 1 808 bp was obtained via a rapid amplification of cDNA ends method, and the sequence was subsequently deposited to GenBank (accession No. JX401571). The CaMBP cDNA of E. dunnii contained a single open reading frame of 1 362 bp, a 5t' untranslated region of 175 bp, and a 3t' untranslated region of 268 bp. Multiple sequence alignment and phylogenetic analysis indicated that CaMBP of E. dunnii shared 56 to 84 % identities with the CaMBPs of other plants and was similar to that of Ricinus communis, Medicago truncatula, and Gossypium hirsutum.

Aluminium toxicity in acid soils is the main limitation to crop production worldwide. In wheat (Triticum aestivum L.), the Al-activated malate transporter (TaALMT1) gene located on chromosome 4DL is associated with malate efflux and Al-tolerance. To introgress Al-tolerance from the breeding line CAR3911 into the high yielding Al-sensitive cultivar Kumpa-INIA, phenotypic and molecular characterizations of gene/QTL underlying Al-tolerance in CAR3911 followed by marker-assisted backcrossing (MAS-BC) were undertaken. Al-tolerant backcross (BC) lines were selected using the functional marker ALMT1-4 designed immediately upstream of the TaALMT1 coding region. Foreground and background selections using ALMT1-4 and microsatellite markers were conducted. Linkage and sequence analyses suggest that the TaALMT1 gene could underly the Al-tolerance in CAR3911, possessing the same promoter type (V) as the Al-tolerant genotypes Carazinho and ET8. The MAS-BC strategy allowed the selection of Al-tolerant lines with the smallest introgressed region (6 cM) on 4D and the highest recurrent parent genome (RPG) (98 %) covering 2 194 cM of the wheat genome. The homozygous BC3F2 line named Kumpa-INIA-TaALMT1 expressed a 3-fold higher Al-tolerance than its isogenic line Kumpa-INIA at 40 μM Al in the hydroponic solution, and similarly to CAR3911 and Carazinho. The MAS-BC strategy was successful for the introgression of the TaALMT1 gene into Kumpa-INIA in only three BC generations, shortening the breeding cycle to 24 months, which promises to increase wheat production and a greater yield stability in the acid soils of Southern Chile.

In many polar and alpine ecosystems, lichens of genus Umbilicaria represent dominant species forming community structure. Photosynthetic and spectral properties of the lichens may change rapidly according to an actual hydration status of their thalli. In this study, we investigated responses of photochemical reflectance index (PRI), normalized difference vegetation index (NDVI), effective quantum yield of photosynthetic efficiency of photosystem (PS) II (Φ_PSII), and several photosynthetic parameters derived from fast induction kinetics of chlorophyll fluorescence (OJIP) to controlled dehydration. We used U. arctica and U. hyperborea collected close to Nuuk, Greenland. In both the species, PRI showed a curvilinear increase with dehydration, i.e., a decreasing water potential (Ψ_w). The increase was apparent within Ψ_w range of 0 to -10 MPa. The PRI increase was less pronounced in U. arctica than in U. hyperborea. NDVI decreased with a progressive thallus dehydration in both the species, however, throughout Ψ_w range of 0 to -30 MPa, U. hyperborea had lower NDVI values than U. arctica. The relationship between Φ_PSII and Ψ_w resulted in a typical S curve. A critical Ψ_w at which photosynthetic processes were fully inhibited was -30 MPa in both the species, however, species-specific differences in the S curve shape were found. Analyses of photosynthetic parameters derived from OJIPs revealed that the absorption of radiation energy and a trapping rate increased with dehydration in active reaction centres of PS II, the number of which decreased with a more pronounced lichen thallus dehydration. It is concluded that U. arctica and U. hyperborea possess effective physiological mechanisms to maintain an effective photosynthesis when partly dehydrated (the Ψ_w range of 0 to -15 MPa). In spite of similar ecological niches that these two lichens occupy in nature, their spectral and photosynthetic properties differred.

Internal transcribed spacer (ITS) regions and maturase K (matK) sequence polymorphisms provide an efficient tool for discrimination and conservation of genetic resources of Anoectochilus species. The objectives of this study were to develop markers specifically distinguishing A. formosanus Hayata from closely related A. koshunensis Hayata, A. roxburghii (Wall.) Lindl., and Ludisia discolor (Ker Gawl.) A. Rich. and to identify a molecular phylogenetic relationship of a new intergeneric BC1F1 hybrid - Ludochilus Jin-Chai. Specific primers for nuclear ITS regions and chloroplast matK sequences were designed and converted into cleaved amplified polymorphic sequence (CAPS) markers. Results show that the matK sequences obtained corresponded to pseudogenes and that their digestion with enzyme HinfI revealed a polymorphic pattern in A. formosanus and A. koshunensis. The pedigree of Lud. Jin-Chai, which was derived from the cross between Lus. discolor and A. formosanus, was also confirmed based on ITS and matK CAPS markers.

Dramatic accumulation of proline is a common physiological response in plants exposed to various abiotic stresses. Accumulation of proline could be due to de novo synthesis, decreased degradation, lower utilization, or hydrolysis of proteins. Extensive intercellular proline transport occurs between the cytosol, chloroplasts, and mitochondria due to its compartmentalized metabolism. Although all functions of proline in stress tolerance are still a matter of debate, it is suggested that proline contributes to stabilization of sub-cellular structures, scavenging free radicals, and buffering cellular redox potential. It also chelates heavy metals, modulates cellular functions, and even triggers gene expression. Apparently, proline acts as stress-related signal exhibiting cross tolerance to a range of different stresses. Besides these significant roles, its metabolism is found to be coupled to several key pathways such as pentose phosphate, tricarboxylic acid, or urea cycles and contributes to, i.e., purine synthesis and the phenylpropanoid pathway. Although the molecular basis of regulation of proline metabolism is still largely obscure, the genetic engineering of proline content could lead to new opportunities to achieve plant stress tolerance.

The protective roles of glutathione (GSH) applied on salt stress-affected mung bean (Vigna radiata L.) seedlings were studied. The salt stress (200 mM NaCl) significantly increased the malondialdehyde (MDA), methylglyoxal (MG), H₂O₂, and proline (Pro) content, O₂ ^.- generation rate, and lipoxygenase (LOX) activity and reduced the leaf relative water content (RWC) and chlorophyll (Chl) content. The salt stress also significantly reduced the ascorbate (AsA) content, increased the endogenous GSH and glutathione disulfide (GSSG) content, and reduced the GSH/GSSG ratio. The activities of mono-dehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and catalase (CAT) decreased; and the activities of ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione peroxidase (GPX) increased under the salt stress. The activities of glyoxalase I (Gly I) and glyoxalase II (Gly II) decreased under the salt stress (except the Gly II activity at 48 h). Mung bean seedlings which were treated with NaCl together with GSH showed an improved AsA and GSH content, GSH/GSSG ratio, higher activities of APX (only at 24 h), MDHAR, DHAR, GR, SOD (only at 24 h), CAT, GPX (only at 48 h), GST (only at 24 h), Gly I and Gly II under the salt stress compared with those treated with NaCl alone. The improved antioxidant and glyoxalase systems by GSH application decreased the MDA, H₂O₂, and MG content, O₂ ^.- generation rate, as well as increased the leaf RWC and Chl content. Thus, exogenous GSH improved the response of the mung bean seedlings to the salt stress.

A pot experiment was conducted in a greenhouse to assess the tolerance of Agropyron cristatum plants to cadmium contaminated soils (0, 5, 10, 25, 50, 100, 150, and 200 mg kg^-1) for 100 d. Results indicate that Cd in concentrations of 5-50 mg kg^-1 had no significant impact on growth, relative membrane permeability (RMP), lipid peroxidation measured as malondialdehyde (MDA) content, and chlorophyll (Chl) content relative to the control. Exposure of these plants to high concentrations of Cd (100-200 mg kg^-1) caused a small reduction in growth and Chl content and a slight enhancement of RMP and MDA content compared with the control. In addition, superoxide dismutase (SOD) and peroxidase (POD) activities show an increasing trend with the increase of Cd content in soil. The Cd content in the roots was 4.7-6.1 times higher than that in the shoots under all Cd treatments suggesting that the plant can be classified as a Cd excluder. The translocation factor was low and similar at 25-200 mg kg^-1 Cd treatments. In summary, A. cristatum plants tolerated Cd stress and might have potential for the phytoremediation of Cd contaminated soils.

Eukaryotic elongation factor Tu has been implicated in responses to heat stress and viral infection. In this study, the turnip mosaic virus (TuMV)-response gene BcLRK01, which encodes a leucine-rich repeat receptor-like kinase, was probed using the cDNA library of TuMV-infected leaves of non-heading Chinese cabbage (Brassica campestris ssp. chinensis). The BcEF-Tu gene, which encodes chloroplast elongation factor Tu, was obtained and verified by a yeast two-hybrid system to interact with the BcLRK01 gene. TuMV infection depressed the expression of this gene, whereas a heat stress induced its expression. Overexpression of BcEF-Tu enhanced the viability of Escherichia coli transformants under the heat stress. These results demonstrate that elongation factor BcEF-Tu responded to the TuMV infection and heat stress. This is the first report on chloroplast EF-Tu in non-heading Chinese cabbage which provides a theoretical basis for the functional research of EF-Tu.

Hydroponic experiments were conducted to investigate the effects of nitrogen forms on nitric oxide accumulation and glycinebetaine (GB) metabolism under osmotic stress (OS) simulated by the addition of polyethylene glycol (PEG-6000) to two maize (Zea mays L.) cultivars Zhengdan 958 (ZD958; drought-tolerant) and Jundan 20 (JD20; drought-sensitive). OS led to the accumulation of NO, GB, and choline, as well as to an increase of betaine aldehyde dehydrogenase (BADH) activity in both the cultivars. The responses of both the maize cultivars to OS were significantly higher under nitrate nutrition than under the mixed supply of ammonium and NO₃ ^- or sole NH₄ ⁺. Cultivar ZD958 was superior to JD20 under the osmotic stress. Furthermore, compared with sole NH₄ ⁺, sole NO₃ ^- and the mixed supply of NH₄ ⁺ and NO₃ ^- increased all the parameters in cv. ZD958 but only the GB and choline content in JD20. Therefore, it is concluded that ZD958 showed a higher accumulation of NO and enhanced GB metabolism under OS than JD20 regardless of N form.

The present study investigated differences in cadmium resistance of two wheat (Triticum aestivum L.) cultivars. The cvs. RAJ 4161 (Cd resistant) and PBW 343 (Cd sensitive) were treated with 200 mg(Cd) kg^-1(soil) for 3, 5, 7, and 10 d. The effect of the Cd stress was estimated by measuring growth parameters, accumulation of cadmium, sulphur, and glutathione (GSH), and by expression of some defence genes [phytochelatin synthase (PCS), glutathione reductase (GR), and ascorbate peroxidase (APX)]. The Cd treatment resulted in a significant reduction in plant growth and in an increase in the accumulation of S and GSH. Further, the expressions of PCS, GR, and APX were also mostly enhanced. The PCS was upregulated significantly in roots of RAJ 4161 (0.6-fold) and downregulated (0.9-fold) in PBW 343 on day 3 of the Cd treatment. In RAJ 4161, the expressions of APX and GR recorded a maximum increase of 2.1- and 2.4-fold in roots and leaves, respectively, after 10 d of the stress. The results show that a different ability of RAJ 4161 and PBW 343 to modulate mRNA expression after the Cd treatment was related to their Cd tolerance.

Plant growth regulators (PRG)-assisted phytoremediation is a technique that could enhance the yield of heavy metal accumulation in plant tissues. So far, a small number of experiments have helped identify three groups of plant hormones that may be useful for this purpose: auxins, cytokinins, and gibberellins. Studies have shown that these hormones positively affect the degree of accumulation of metallic impurities and improve the growth and stress resistance of plants. This review summarizes the present knowledge about PGRs' impact on phytoextraction yield.

The effects of abiotic stresses on the expression of Lhcb1 gene (coding light-harvesting chlorophyll-protein complex II), and on photosynthetic rate were studied in one Oenanthe javanica (cv. Baguazhou Shuiqin) and three Apium graveolens cultivars (Liuhe Huangxinqin, Jinnan Shiqin, and Ventura). The Lhcb1 genes were cloned and we predicted that Lhcb1 proteins were most probably able to form homo-trimers. Each monomer contained five helical segments, of which three were likely transmembrane helices, and 15 putative chlorophyll-binding sites. The abiotic stresses affected the A. graveolens similarly in all the cultivars, however, the O. javanica photosynthesis was not significantly affected. The expression of the Lhcb1 gene was up-regulated under the cold, heat, salt, and drought stresses in the cvs Liuhe Huangxinqin and Jinnan Shiqin. The Lhcb1 was up-regulated under the heat, salt, and drought stresses in the cv. Ventura, whereas had no significant changes under the cold stress. No significant changes of the Lhcb1 expression were found under the cold and salt stresses and even little down-regulation following the heat and drought stresses in Oenanthe javanica. The expression of Lhcb1 may be a useful indicator of photosynthetic activity.

Feverfew (Tanacetum parthenium) is a medicinal plant belonging to the Asteraceae family. To improve understanding terpene metabolism in feverfew, the relative gene expression of four key genes coding 3-hydroxy-3-methylglutarylcoenzyme A reductase (HMGR) and germacrene A synthase (GAS) from the mevalonic acid pathway (MVA), as well as 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) and hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (HDR) from the methyl erythritol phosphate pathway (MEP), were examined. Target organs and tissues included young leaves (not fully expanded), mature leaves (fully expanded), flowers, stems, roots, and glandular trichomes. HMGR, DXR, and HDR were isolated and sequenced for the first time in feverfew. Real-time quantitative PCR analysis revealed differential expression of these genes in feverfew tissues and developmental stages.

Salinity is one of the most severe problems in worldwide agricultural production. The effect of salt on dry mass, total glutathione content, its regulatory enzymes, and extent of DNA damage in growing mungbean (Vigna radiata L. Wilczek) seedlings was investigated. The salt stress decreased a dry mass accumulation in the seedlings. A total glutathione (GSH) content and the activities of the enzymes of GSH metabolism were adversely affected by the salt stress. The enhanced accumulation of reactive oxygen species under the NaCl stress caused an increase in DNA damage, measured using a comet assay, in both roots and leaves of the mungbean seedlings. The pretreatment of mungbean seeds with a sublethal dose of NaCl was able to overcome the adverse effects of the salt stress to variable extents by exhibiting significant alterations of all tested parameters, imparting better growth and metabolism of the mungbean seedlings.

Male sterile line is a useful material for hybridization, but its sterility mechanism, especially proteomic profile, is still not entirely clear. In wheat (Triticum aestivum L.), a male sterile Bainong (BNS) genotype whose sterility could be manipulated by temperature was recently selected. We focused on the proteomic profile change of anthers from the male sterile line (SL) and its conversional line (CL). Two-dimensional gel electrophoresis and MALDI-TOF-MS technologies were utilized for proteomic profiles analysis. Differently abundant protein spots (over 2-fold, P < 0.05) were selected for identification analysis. Compared to CL, 24 up-regulated and 23 down-regulated proteins were identified in SL. Protein metabolism-related proteins, which included a ubiquitin-conjugating enzyme E2 (23 kDa) and an ATP-dependent Clp protease proteolytic subunit, were over-accumulated in SL anthers. Alcohol dehydrogenase ADH1A, fructose-bisphosphate aldolase, chloroplast fructose-bisphosphate aldolase, and NADP-dependent malic enzyme were notably down-regulated in SL anthers. Up-regulated prohibitin protein Wph and a translationallycontrolled tumor protein homolog, and down-regulated histone acetyltransferases HAT1 and HAT2, and DNA directed RNA polymerase subunit α were identified in SL anthers. These dramatically changed proteins may play a crucial role in abnormal anther development and pollen abortion in BNS.

Jatropha curcas L. is a plant with various commercial uses, and drought is an important limiting factor for its distribution and production. In this study, we investigated the role of drought hardening in an increased drought tolerance in J. curcas, and the involvement of osmoregulation and biochemical pathways in this enhanced tolerance. Results show that a drought hardening treatment with 10 % (m/v) polyethylene glycol 6000 for two days significantly increased a survival rate, decreased the content of malondialdehyde, and alleviated electrolyte leakage in the J. curcas seedlings under the drought stress. Measurements of leaf water potential, osmotic potential, and pressure potential show that this drought hardening treatment can improve the water status of J. curcas seedlings during the early phase of drought stress. In addition, the drought hardening treatment gradually increased the concentrations of compatible solutes proline, glycinebetaine, and soluble sugars during drought hardening and subsequent drought stress. It also clearly raised the activity of betaine aldehyde dehydrogenase, a key enzyme for the glycinebataine biosynhthesis as well as the activity of enzymes Δ₁-pyrroline-5-carboxylate synthetase (P5CS), glutamate dehydrogenase, arginase, and ornithine aminotransferase, all key enzymes in the proline biosynthesis. The expression of P5CS gene in the J. curcas seedlings also increased during drought hardening and subsequent drought stress, but the activity of proline dehydrogenase decreased. These results show that the drought hardening treatment can enhance drought tolerance in J. curcas, and osmoregulation is a key factor in this increased drought tolerance.

In the present study, we found that the expression patterns of the vegetative profilins and actin depolymerizing factors (ADFs) were specifically altered under low temperature (17 °C) stress using a real-time PCR. Our results show that also reorganization of the actin cytoskeleton was triggered by a low temperature. Facilitation of microfilament (MF) assembly by phalloidin treatment resulted in an enhanced low temperature stress tolerance, whereas blocking MF assembly with latrunculin B resulted in enhanced low temperature stress sensitivity. Our results show that the specific members of the vegetative profilins and ADFs might participate in regulating the response of plants to a low temperature stress, and the actin cytoskeleton is vital for the tolerance of Arabidopsis seedlings to low temperature stress.

Cassava (Manihot esculenta Crantz) is an important crop and it is significantly affected by water stress. The computational analysis of cis-regulatory elements in promoter regions of 21 drought-responsive miRNA gene families and 35 miRNA-target genes in cassava indicated some elements relevant to drought stress responses. To investigate the role of miRNAs and target genes in responses to a water deficit in cassava in more detail, in vitro plantlets were subjected to an imitated water deficit by 40 % polyethylene glycol. Using RT-qPCR, the differential expression of the cassava miR164/MesNAC and miR167/MesARF6/8 were observed to be associated with changes in the leaf shape, stomatal closure, and relative water content. The modified 5'-RNA ligase-mediated rapid amplification of cDNA-end (5'RLM-RACE) experiment confirmed MesNAC and MesARF8 as the in vivo-target genes of miR164 and miR167, respectively, in cassava leaf. The possible functions of miR164 and miR167-target genes in response to water deficit are discussed.

To investigate whether brassinosteroids (BR) affects cytokinin (CK)-induced anthocyanin biosynthesis, seedlings of the Arabidopsis dwarf4 (dwf4) mutants including partially suppressing coi1 (psc1) and dwf4-102, which are defective in the BR biosynthesis, and the brassinosteroid-insensitive 1-4 (bri1-4) mutant defective in BR signalling were used for the analysis of CK-induced anthocyanin accumulation and the expression of anthocyanin biosynthetic genes and WD-repeat/Myb/bHLH transcription factors. The results show that the CK-induced anthocyanin accumulation was remarkably reduced in dwf4 and bri1-4 mutants, but distinctly increased in the wild type (WT) treated with BR. Moreover, the CK-induced expressions of the late anthocyanin biosynthetic genes including dihydroflavonol reductase, leucoanthocyanidin dioxygenase, and UDP-glucose: flavonoid-3-O-glucosyl transferase were significantly reduced in bri1-4 and dwf4-102 mutants compared to WT. In addition, the expressions of transcription factors production of anthocyanin pigment 1 (PAP1), glabra 3 (GL3), and enhancer of glabra 3 (EGL3) were induced by CK in WT but not in the bri1-4 and dwf4-102 mutants. These results indicate that BR enhanced the CK-induced anthocyanin biosynthesis by up-regulating the late anthocyanin biosynthetic genes and this regulation might be mediated by the transcription factors PAP1, GL3, and EGL3.