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BackgroundCuticular wax plays important role in protecting plants from drought stress. In ArabidopsisWRI4improves drought tolerance by regulating the biosynthesis of fatty acids and cuticular wax.Cyperus esculentus(yellow nutsedge) is a tough weed found in tropical and temperate zones as well as in cooler regions. In the current study, we report the molecular cloning of aWRI4-like gene fromCyperus esculentusand its functional characterization in Arabidopsis.ResultsUsing RACE PCR, full-lengthWRI-like gene was amplified from yellow nutsedge. Phylogenetic analyses and amino acid comparison suggested it to be aWRI4-like gene. According to the tissue-specific expression data, the highest expression ofWRI4-like gene was found in leaves, followed by roots and tuber. Transgenic Arabidopsis plants expressing nutsedgeWRI4-like gene manifested improved drought stress tolerance. Transgenic lines showed significantly reduced stomatal conductance, transpiration rate, chlorophyll leaching, water loss and improved water use efficiency (WUE). In the absence of drought stress, expression of key genes for fatty acid biosynthesis was not significantly different between transgenic lines and WT while that of cuticular wax biosynthesis genes was significantly higher in transgenic lines than WT. The PEG-simulated drought stress significantly increased expression of key genes for fatty acid as well as wax biosynthesis in transgenic Arabidopsis lines but not in WT plants. Consistent with the gene expression data, cuticular wax load and deposition was significantly higher in stem and leaves of transgenic lines compared with WT under control as well as drought stress conditions.ConclusionsWRI4-like gene fromCyperus esculentusimproves drought tolerance in Arabidopsis probably by promoting cuticular wax biosynthesis and deposition. This in turn lowers chlorophyll leaching, stomatal conductance, transpiration rate, water loss and improves water use efficiency under drought stress conditions. Therefore,CeWRI4-like gene could be a good candidate for improving drought tolerance in crops.

Background Eruca vesicaria subsp. sativa is one of the Cruciferae species most tolerant to drought stress. In our previous study some extremely drought-tolerant/sensitive Eruca lines were obtained. However little is known about the mechanism for drought tolerance in Eruca. Methods In this study two E. vesicaria subs. sativa lines with contrasting drought tolerance were treated with liquid MS/PEG solution. Total RNA was isolated from 7-day old whole seedlings and then applied to Illumina sequencing platform for high-throughput transcriptional sequencing. Results KEGG pathway analysis indicated that differentially expressed genes (DEGs) involved in alpha-Linolenic acid metabolism, Tyrosine metabolism, Phenylalanine, Tyrosine and tryptophan biosynthesis, Galactose metabolism, Isoquinoline alkaloid biosynthesis, Tropane, Piperidine and pyridine alkaloid biosynthesis, Mineral absorption, were all up-regulated specifically in drought-tolerant (DT) Eruca line under drought stress, while DEGs involved in ribosome, ribosome biogenesis, Pyrimidine metabolism, RNA degradation, Glyoxylate and dicarboxylate metabolism, Aminoacyl-tRNA biosynthesis, Citrate cycle, Methane metabolism, Carbon fixation in photosynthetic organisms, were all down-regulated. 51 DEGs were found to be most significantly up-regulated (log2 ratio ≥ 8) specifically in the DT line under PEG treatment, including those for ethylene-responsive transcription factors, WRKY and bHLH transcription factors, calmodulin-binding transcription activator, cysteine-rich receptor-like protein kinase, mitogen-activated protein kinase kinase, WD repeat-containing protein, OPDA reductase, allene oxide cyclase, aquaporin, O-acyltransferase WSD1, C-5 sterol desaturase, sugar transporter ERD6-like 12, trehalose-phosphate phosphatase and galactinol synthase 4. Eight of these 51 DEGs wre enriched in 8 COG and 17 KEGG pathways. Conclusions DEGs that were found to be most significantly up-regulated specifically in the DT line under PEG treatment, up-regulation of DEGs involved in Arginine and proline metabolism, alpha-linolenic acid metabolism and down-regulation of carbon fixation and protein synthesis might be critical for the drought tolerance in Eruca. These results will be valuable for revealing mechanism of drought tolerance in Eruca and also for genetic engineering to improve drought tolerance in crops.

Water deficit is an environmental factor that constrains crops to express their ecophysiological potential and causes crop yield reduction. Eruca vesicaria has been reported to be one of the most drought-tolerant species in Cruciferae. In this study, polyethylene glycol-simulated drought tolerance was evaluated in one line of Brassica carinata, one line of Brassica napus and 249 Eruca lines based on the principal component analysis (PCA) and unweighted pair-group arithmetic average (UPGMA) cluster analysis. The PCA based on eight drought tolerance indices indicated that the first three components accounted for 85.46% of the total variation, with principal component (PC) 1 accounting for 43.89%, PC2 for 27.85% and PC3 for 13.73% of the total variation. The UPGMA cluster analysis indicated that B. napus cultivar Zhongshuang 9 and Eruca lines could be clustered into five major groups, with group 1 being, in general, drought sensitive, group 2 being slightly–medium drought tolerant, group 3 being drought tolerant, group 4 being highly drought sensitive and group 5 being highly drought tolerant. B. carinata cultivar XB1, as an outstander, showed high drought sensitivity. The UPGMA cluster dendrogram provides a good representation of the similarity matrix (r= 0.68). The drought-tolerant Eruca materials obtained in this study will be valuable for genetic improvement not only in Eruca itself, but also in Brassica crops since they are drought-tolerant lines from a drought-tolerant species.

ADP-glucose pyrophosphorylase (ADPGlcPPase) controls the first committed step of starch synthesis by catalyzing the biosynthesis of ADP-glucose from glucose-phosphate and ATP. It is a tetrameric protein consisting of two small and two large subunits. The small subunits have a catalytic function, while the large subunits regulate the enzyme activity. Cyperus esculentus (yellow nutsedge) is a perennial C4 plant grown from rhizomes and tubers. Previous studies on yellow nutsedge have mostly focused on the morphology and cultivation of tubers, their application in food, and biochemical analyses of the tubers. In this study, the gene encoding the ADPGlcPPase small subunit (CeAGPS) in yellow nutsedge was cloned and characterized. The full-length CeAGPS cDNA sequence contained an 81-bp 5'-untranslated region (UTR), a 188-bp 3'-UTR, and a 1539-bp open reading frame encoding 512-amino acid residues. The genomic sequence of CeAGPS comprises a nine exon-eight intron structure similar to the previously reported cotton and Arabidopsis thaliana AGPS genes. The deduced translation product of the CeAGPS gene contained a well-conserved catalytic domain and regulatory elements typical of plant AGPS. Reverse transcriptase polymerase chain reaction amplification of the target gene in various plant parts using gene-specific primers indicated that the expression of CeAGPS was most abundant in the tuber, and relatively lower in nutsedge roots.

The influence of essential (Cu, Ni and Zn) and non-essential heavy metals (Hg, Cr, Pb and Cd) on seed germination and early seedling growth in industrial oil crop Crambe abyssinica was evaluated under laboratory conditions. Our results indicated that among the 7 heavy metals tested only Cu and Hg significantly (P < 0.01) decreased Crambe seed germination in a dose-dependent manner at higher concentrations while certain Cr concentrations significantly increased the seed germination (P < 0.05). All the 7 heavy metals decreased significantly relative root length, shoot length and fresh seedling weight in a dose-dependent manner (P < 0.01). The heavy metals except Ni decreased relative root length first, then shoot length or fresh seedling weight, and finally seed germination. Ni seemed to influence the relative fresh seedling weight first, then shoot length, root length and finally seed germination at lower concentrations, but the decrease in relative root length became faster when the Ni concentrations were increased. Our results indicated that Crambe is tolerant or moderately tolerant to the heavy metals tested except Ni and can be improved for phytoremediation of soils contaminated by heavy metals.

In this paper, interspecific crosses among Crambe abyssinica, Crambe hispanica, and Crambe kralikii were reported. In the C. hispanica x C. abyssinica (H x A) cross, 118 F1 hybrids were produced without embryo rescue, while 5 F1 hybrids were obtained with embryo rescue, when C. hispanica was used as the female parent. In the reciprocal cross (A x H), 232 hybrids were obtained without embryo rescue. From more than 1000 C. kralikii flowers pollinated with pollen grains of C. abyssinica (K x A), only 2 F1 hybrids were obtained with embryo rescue, whereas the reciprocal cross produced no hybrids, even with embryo rescue. The hybrids were confirmed at the morphological, cytological, and molecular levels. In the combinations of A x H and H x A, many BC1 hybrids were obtained without embryo rescue. In contrast, in the K x A cross, only 7 BC1 plants were obtained with embryo rescue, while no seed set was achieved under self-pollination or in backcrosses without embryo rescue. In the H x A F1 hybrids, the pollen stainability was 65.4-86.0%, with an average of 76.9%. In comparison, the pollen viability of hybrids in the reciprocal cross (A x H) ranged from 66.2 to 81.1%, with an average of 75.4%. Fertile pollen grains were not found in the K x A F1 hybrids. All F1 hybrids of the 3 crosses (H x A, A x H, and K x A) had the expected 2n = 75 chromosomes. AFLP analyses indicated that all F1 hybrids and their progenies had typical bands of the parents. These hybrids and progenies are anticipated to be valuable for future C. abyssinica improvement in breeding programs.

In this paper the salt tolerance in Brassicas and some related species was compared. When seedlings germinated on sand cultures with liquid MS medium were considered, the relative germination rate, root length, shoot length and fresh seedling weight were significantly correlated with each other (P < 0.01), and only the relative shoot lengths were significantly different among the tested genotypes (P < 0.05); When both seedlings germinated on MS and MS plus 0.4% NaCl were considered, only the relative shoot length of seedlings germinated on MS was significantly different from that germinated on MS + 0.4% NaCl (P < 0.05), and also only the relative shoot lengths were significantly different among the tested genotypes (P < 0.01). Raphanus sativa cv. Changfeng, B. juncea cv. JC and Brassica napus cv. ZS 10 showed low salt tolerance in terms of relative germination rate, root length, shoot length and fresh seedling weight; B. oleracea cv. JF-1, Sinapis alba cv. HN-2 showed high salt tolerance in terms of relative germination rate, root length, shoot length and fresh seedling weight. Based on our result we suggest that relative shoot length might be convenient to rank the salt tolerance but cluster analysis based on multiple parameters of relative germination rate, root length, shoot length and fresh seedling weight might be more accurate in screening for salt tolerance in Brassicas and related species.

Eruca vesicaria subsp sativa is one of the most tolerant Cruciferae species to drought, and dehydration-responsive element-binding protein 2A (DREB2A) is involved in responses to salinity, heat, and particularly drought. In this study, a gene encoding EvDREB2A was cloned and characterized in E. vesicaria subsp sativa. The full-length EvDREB2A cDNA sequence contained a 388-bp 5'-untranslated region (UTR), a 348-bp 3'-UTR, and a 1002-bp open reading frame that encoded 334 amino acid residues. The theoretical isoelectric point of the EvDREB2A protein was 4.80 and the molecular weight was 37.64 kDa. The genomic sequence of EvDREB2A contained no introns. Analysis using SMART indicated that EvDREB2A contains a conserved AP2 domain, similar to other plant DREBs. Phylogenetic analysis revealed that EvDREB2A and DREB2As from Brassica rapa, Eutrema salsugineum, Arabidopsis thaliana, Arabidopsis lyrata, and Arachis hypogaea formed a small subgroup, which clustered with DREB2Bs from A. lyrata, A. thaliana, Camelina sativa, and B. rapa to form a larger subgroup. EvDREB2A is most closely related to B. rapa DREB2A, followed by DREB2As from E. salsugineum, A. thaliana, A. hypogaea, and A. lyrata. A quantitative real-time polymerase chain reaction indicated that EvDREB2A expression was highest in the leaves, followed by the roots and hypocotyls, and was lowest in the flower buds. EvDREB2A could be used to improve drought tolerance in crops.

Nicotianamine (NA) is a ubiquitous metabolite in plants that bind heavy metals, is crucial for metal homeostasis, and is also an important metal chelator that facilitates long-distance metal transport and sequestration. NA synthesis is catalyzed by the enzyme nicotianamine synthase (NAS). Eruca vesicaria subsp sativa is highly tolerant to Ni, Pb, and Zn. In this study, a gene encoding EvNAS was cloned and characterized in E. vesicaria subsp sativa. The full-length EvNAS cDNA sequence contained a 111-bp 5'-untranslated region (UTR), a 155-bp 3'-UTR, and a 966-bp open reading frame encoding 322-amino acid residues. The EvNAS genomic sequence contained no introns, which is similar to previously reported NAS genes. The deduced translation of EvNAS contained a well-conserved NAS domain (1-279 amino acids) and an LIKI-CGEAEG box identical to some Brassica NAS and to the LIRL-box in most plant NAS, which is essential for DNA binding. Phylogenetic analysis indicated that EvNAS was most closely related to Brassica rapa NAS3 within the Cruciferae, followed by Thlaspi NAS1, Camelina NAS3, and Arabidopsis NAS3. A reverse transcription-polymerase chain reaction indicated that EvNAS expression was greatest in the leaves, followed by the flower buds and hypocotyls. EvNAS was moderately expressed in the roots.