Cotton CBF Transcriptional Activator Cloning And Its Role In Cold Acclimation And Freezing Tolerance

Cold temperature induces great damage during the crop growth. Every year there are nearly two hundred billion US dollar lost in the world because of it. In north China cotton(Gossypium hirsutum L.) plant areas, especially in Xinjiang areas, cold temperature is one of the most important limiting factors in cotton growth. Spring low temperature will delay the seedtime and Autumn low temperature will influence the quality of the cotton fibre.Several difference genes control freezing tolerance in plants. Only transcription factor can activate several genes expression in the same time, then it can improve the ability of plant clod tolerance. A lot of work focus on transcription factors in recently. Transcription factors are proteins that direct and regulate the expression of specific genes or entire pathways of genes in eukaryotes. They are an essential and key controlling component of gene specific expression patterns in response to developmental, hormonal and environmental cues. Generally they perform this function by binding to a target site in the promoter of the regulated gene and then activating that gene's expression through recruitment of RNA polymerase and the other more general transcription factors to the target gene's promoter. The Arabidopsis thaliana C-repeat binding factors (CBFs) are one such family of proteins. These proteins play an integral role in the ability of plants to cold acclimate and increase in freezing tolerance. They perform this function by binding to the CRT/DRE, a cis-acting element present in the promoters of the Arabidopsis cold-regulated (COR) genes and then activating COR gene expression. The CBFs are not unique to Arabidopsis however as cDNAs encoding proteins highly identical have been identified in a number of species across the plant kingdom. There is no report about cotton CBF gene.China has become one of the largest cotton producers in the world. Low temperature causes the loss of cotton yield and quality. It is important work on the cotton cold tolerance. We are currently isolating the CBF loci from cotton. In this job, we clone a CBF gene from different cotton varieties (Zhongl2. Zhong36 and Hai7124) genomic DNA which is named pYX1, pYX2, pYX3, sequence those clones, find that they have the CBF signature sequences. DNA homologous analysis showed there was 97% identity between those three CBF from different cotton varieties, had 63% identity with Arabidopsis, 68% identity with tomato, 69% identity with medicago and 40% identity with barley. Cotton genomic DNA southern blot analysis indicated that CBF had 3-5 family members in cotton. The cotton CBF we cloned was found to be cold-inducible by Northern blot. After 4h of exposing cotton seedling to low temperature, CBF had expression signal. We also constructed CBF plant expression vector by using 35S promoter or NOS promoter, named pYX4 and pYX5, transfer this gene into cotton by pollen tube pathway, the further selection is in processing.