The Function Analysis Of Cotton BI-1(Bax Inhibitor-1) Under Biotic And Abiotic Stress

PCD is an essential biological process for organisms not only in normal developmentand ageing but also in maintenance of homeostasis and in response to stresses andpathogen insults. BI-1(Bax inhibitor-1) encoded a protein inhibitor of the PCDtranscription factor, BAX. BI-1gene functions to inhibit apoptosis caused by drought,high salt and pathogen stress in many plants. Based on the previous studies of BI-1gene, we supposed that GhBI-1should be function in stress tolerance and disease ofresistance. The previous work in our lab has proved that GhBI-1could respond tobiotic and abiotic stress signals. To further investigate the biological functions ofGhBI-1in response to biotic and abiotic stress, we undertook the followingresearches:1. Based on the precious work, CaMV35S promoter drived GhBI-1A and GhBI-1Btransgenic Arabidopsis were screened and propagated to T3generation respectively.The transgenic lines were treated by different biotic and abiotic stresses. Controlledby the wild type, the transgenic Arabidopsis were treated with series concentration ofsalt in different developmental stages. The results show that salt tolerance of alltransgenic plants has been improved. The germination stage of GhBI-1A transgenicplants showed obvious advantages in salt tolerance compared with GhBI-1Atransgenic plants. There were no obvious difference in mature stage of transgenicplants and wild type under the salt tolerance. The roots of transgenic plants werestronger than wild type when treated by5mg/L tunicamycin. It indicates thatoverexpression of GhBI-1A and GhBI-1B can improve the tolerance of thetunicamycin stress in transgenic Arabidopsis. GhBI-1A transgenic plants were foundto be better than GhBI-1B transgenic plants in recovery experiments after tunicamycintreatment. Leaves of transgenic plants were treated by crude toxin of Verticilliumdahliae to evaluate the fungal tolerance. There was no difference between wild typeand transgenic plants.2. Based on the cDNA sequence of GhBI-1A and GhBI-1B gene, promoter sequencesof the two genes were isolated by genomewalker with1650bp and2001bp respectively. Through the forecast of two promoter sequences of cis-acting element,inducible elements are existed in both the sequence structures, indicating that the twopromoters are both inducible promoters. It is noted that considerable differences of theinducible cis-acting elements are existed between the two promoters, supposing thatthe genes might respond to different biotic and/or abiotic stress signals.3. Biqnary vectors were constrcted by using the two promoters driving GUS gene.Transient expression in tobaccoindicated that the two sequences have promoteractivity. Functions of GhBI-1A and GhBI-1B promoters were further researchedthrough stable expression in transgenic tobacco. The transgenic tobacco was stainedby x-gluc after treated separately with200mM NaCl and5mg/ml TM. The resultsshowed that the activities of the two promoters were both improved after treatments.And the activity of GhBI-1A promoter was increased more than that of GhBI-1Bpromoter under TM treatment.GhBI-1A and GhBI-1B genes were primarily proved to enhance abiotic and bioticstress tolerance by ectopic expression in the model plant, which is consistented withthe research of the gene in other plants. The activities of the two promoters were bothup-regulated under the stress of salt and tunicamycin in the promoter drived gustransgenic tabacco And theGhBI-1A promoter might play the major role in response totunicamycin stress.