| Plant growth is greatly affected by environmental stresses. The expression of a number of genes is induced by both salt and low temperature, although these stresses are quite different. Plant tolerances to stresses, such as high-salt and low-temperature, comprise a number of challenging topics in the fields of plant molecular biology. Many genes involving in the response of plant to stress have been cloned and characterized in the past decade. In this paper, we isolated and characterized three stress-induced genes from cotton. The main results are as follews:1. Based on the conservation region sequences of known DREB genes from other plant species, two cDNA fragments were amplified from leaves of Gossypium hirsutum treated with 200mM NaCl for 6 h by PCR technique using degenerate primers. Their 5'- and 3'-end cDNAs were then obtained by RACE, respectively. The full-length cDNAs contain 1103 and 957 nucleotides and encode two polypeptides of 216 amino acids with a EREBP/AP2 domain. Based on their homology compared with other plant DREB cDNAs and each other, we named them as GhDREB1A and GhDREB1B {Gossypium hirsutum dehydration responsive element binding protein GhDREBl A and B, GenBank accession number: AY321150 and AY422828). No any intron was detected in the two cDNAs by PCR analysis using genomic DNA as template.By the analysis of informatics, the space-structure of protein encoded by GhDREB1s was predicted successfully. There are a a-helix which probably bound to the sequence of DNA.and three β-folds found in this struture. This structure is a typical model of transcriptional factor.2. Northern blot analysis demonstrated that the expression of GhDREB1 was induced by low temperature and salt stress in cotton seedling. mRNA accumulation of GhDREBl in cotton seedling reached a peak at 2hafter 4°C treatment. In order to determine whether GhDREBls expresses specially in different organs, the total RNA were extracted from root, tem and leaf respectively, and the subsequent result of Northern blot suggested that its expression in root was lower evidently than that in leaf, and its expression couldn't be detected in stem.3. To investigate the copy number of GhDREBls in cotton genome, a southern blot experiment was carried out. Our result suggested that GhDREBl might be a small gene family in cotton.4. To further understand the regulation of GhDREBl expression, we isolated a 768bp up-stream promotor sequence of GhDREBlB. Promoter sequence analysis indicted that except for the common promotor motifs, such as CAATBOX, GATABOX and TATABOX, many other kinds of promotor motifs existed in this sequence, for instance, Dof protein binding site, MYB/MYC-like protein binding site, low-responsive motif. These suggested that the cotton DREB1 protein maybe involve into some signal transduction pathway.5. In order to investigate the function of GhDREBlA/B, we constructed a transcriptional fusion between the CaMV35S promoter and the GhDREBl coding region in sense orientation. Seven transgenic tobacco plants were obtained. Northern blot result showed that GhDREBl mRNA accumulation increased compared with wild-type plants. Transgenic plants displayed dwarf phenotype and lower photosynthetic activity. More interestingly, higher tolerance to low-temperature and high-salt stress was observed in transgenic plants.6. Glycine betaine is one of the nontoxic and organic osmolytes which can accumulate rapidly in many plants under salt and other stresses. It plays an important role in maintaining osmotic balance and protecting some important enzymes in plant cells. A Gossypium hirsutum betaine-aldehyde dehydrogenase cDNA GhBADH (GenBank accession number:AY461804), was cloned in salt-treated cotton seedling. The full-lengh cDNA is 1834 bp,putatively encoding 503 amino acids, which share high similarity to AtBADH. Investigation about its biological role in cotton tolerance to stress is in progress.
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