Late embryogenesis-abundant (LEA) proteins are a large and highly diverse family believed to function in normal plant growth and development, and in protecting cells from abiotic stress. This study presents a characterisation of 74 Solanum tuberosum LEA (StLEA) proteins belonging to nine groups. StLEA genes have few introns (≤2) and are distributed on all chromosomes, occurring as gene clusters on chromosomes 1, 2, and 10. All four StASR (StLEA7 group) genes were concentrated on chromosome 4, suggesting their evolutionary conservation on one chromosome. Expression profiles of StLEA genes, in different tissues and in response to hormone and stress treatments, indicated that 71 StLEA genes had differential expression levels, of which 68 StLEA genes were differentially expressed in response to hormones and stress exposure in the potato. Continuous high expression of StASR-2, StLEA3-3, StDHN-3, StLEA2-29, and StLEA2-14 in different tissues indicated their contribution to plant development processes. StLEA2-14, StLEA2-31, StLEA3-3, StASR-1, and StDHN-1 were upregulated by six abiotic stresses, showing their tolerance to a wide spectrum of environmental stresses. Expression analysis of 17 selected StLEA genes in response to drought, salt, heavy metal, heat, and cold treatments by quantitative real-time polymerase chain reaction indicated that StLEA proteins may be involved in distinct signalling pathways. Taken together, StLEA3, StDHN, and StASR subgroup genes may be excellent resources for potato defence against environmental stresses. These results provide valuable information and robust candidate genes for future functional analysis aimed at improving the stress tolerance of the potato.

Jatropha curcas L., also called the Physic nut, is an oil-rich shrub with multiple uses, including biodiesel production, and is currently exploited as a renewable energy resource in many countries. Nevertheless, because of its origin from the tropical MidAmerican zone, J. curcas confers an inherent but undesirable characteristic (low cold resistance) that may seriously restrict its large-scale popularization. This adaptive flaw can be genetically improved by elucidating the mechanisms underlying plant tolerance to cold temperatures. The newly developed Illumina Hiseq™ 2000 RNA-seq and Digital Gene Expression (DGE) are deep high-throughput approaches for gene expression analysis at the transcriptome level, using which we carefully investigated the gene expression profiles in response to cold stress to gain insight into the molecular mechanisms of cold response in J. curcas. In total, 45,251 unigenes were obtained by assembly of clean data generated by RNA-seq analysis of the J. curcas transcriptome. A total of 33,363 and 912 complete or partial coding sequences (CDSs) were determined by protein database alignments and ESTScan prediction, respectively. Among these unigenes, more than 41.52% were involved in approximately 128 known metabolic or signaling pathways, and 4,185 were possibly associated with cold resistance. DGE analysis was used to assess the changes in gene expression when exposed to cold condition (12°C) for 12, 24, and 48 h. The results showed that 3,178 genes were significantly upregulated and 1,244 were downregulated under cold stress. These genes were then functionally annotated based on the transcriptome data from RNA-seq analysis. This study provides a global view of transcriptome response and gene expression profiling of J. curcas in response to cold stress. The results can help improve our current understanding of the mechanisms underlying plant cold resistance and favor the screening of crucial genes for genetically enhancing cold resistance in J. curcas.

Potato is an important food crop and its production is susceptible to drought. Drought stress in crop growth is usually multiple- or long-term. In this study, the drought tolerant potato landrace Jancko Sisu Yari was treated with drought stress, rehydration and re-dehydration, and RNA-seq was applied to analyze the characteristics of gene regulation during these treatments. The results showed that drought-responsive genes mainly involved photosynthesis, signal transduction, lipid metabolism, sugar metabolism, wax synthesis, cell wall regulation, osmotic adjustment. Potato also can be recovered well in the re-emergence of water through gene regulation. The recovery of rehydration mainly related to patatin, lipid metabolism, sugar metabolism, flavonoids metabolism and detoxification besides the reverse expression of the most of drought-responsive genes. The previous drought stress can produce a positive responsive ability to the subsequent drought by drought hardening. Drought hardening was not only reflected in the drought-responsive genes related to the modified structure and cell components, but also in the hardening of gene expression or the “memory” of drought-responsive genes. Abundant genes involved photosynthesis, signal transduction, sugar metabolism, protease and protease inhibitors, flavonoids metabolism, transporters and transcription factors were subject to drought hardening or memorized drought in potato.

Temperature remarkably affects the growth and metabolism of plants. Tobacco is an important cash crop, and the long-term effects of different growth temperatures (18.5, 23.5 and 28.5 °C, daily average) on growth, development and plastid pigments metabolism of tobacco plants were investigated in this study. Compared with tobacco plants grown under 23.5 °C, treatments with 18.5 and 28.5 °C inhibited the expansion of leaves. The contents of superoxide anion (O 2 ·− ), hydrogen peroxide (H2O2) and malonaldehyde (MDA) in the leaves were significantly increased under 28.5 °C from 0 to 60 days, which in turn accelerated the flowering and senescence of tobacco plants. By contrast, the treatment with 18.5 °C remarkably decreased O 2 .− , H2O2 and MDA, and delayed the flowering and senescence. Furthermore, treatment with 18.5 °C significantly up-regulated the expression of glutamyl-tRNA reductase (Glu-TR) and magnesium chelatase (MgCH), and down-regulated the ferri chelatase (FeCH), protochlorophyllide oxidoreductase, chlorophyllase (CHLase), phaeophorbide a monooxygenase (PaO) and phytoene synthase (PSY), which further promoted the accumulation of chlorophyll (Chls) and reduced the carotenoids (Cars) in leaves. On the contrary, exposing to 28.5 °C remarkably down-regulated the Glu-TR and MgCH, and up-regulated the FeCH, CHLase, PaO and PSY, which in turn decreased the Chls and increased the Cars in tobacco leaves. As compared with the plants grown under 23.5 °C, lower (18.5 °C) and higher (28.5 °C) growth temperature inhibited the growth of tobacco plants. In general, treatment with 28.5 °C accelerated the flowering and senescence of tobacco plants by enhancing the accumulation of O 2 .− and H2O2 in leaves, while exposing to 18.5 °C had the opposite effects. Treatment with 18.5 °C increased the content of Chls and reduced the Cars in leaves. In contrast, Treatment with 28.5 °C decreased the Chls and increased the Cars. Moreover, both O 2 .− and H2O2 took part in the breakdown of Chls in tobacco leaves to some extent. The results suggest that growth temperature could regulate growth, development, and plastid pigments metabolism, and 23.5 °C could be an optimal temperature for growth, development and metabolism of plastid pigments of tobacco plants under the experimental conditions.

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.