Cloning And Function Analysis Of MaMYB Drought Resistant

Banana is a perennial herbaceous plant, which likes high temperature and humidity. The leaves become thinner, the growth is delay and the product is reduced when be lacking of water. Since banana is often affected by various stress factors, the study of expression of plant gene under abiotic stress is helpful to understand the mechanism of varieties with resistance, and it provides the theoretical basis for the breeding of resistant varieties. The results of many studies showed that plant MYB transcription factor was involved in various responses to biotic or abiotic stress, and played an important role in plant growth and development and stress-resistance. For this purpose, we have obtained a new MYB gene from banana (Musa acuminate L.AAA group cv.Brazilian) root cDNA library, named MaMYB (accession number: EMK15073.1). In order to enrich the gene resources of banana MYB, this study preliminary forecasts the gene structure and functions. The main results are as follows:1. The MaMYB gene was cloned from banana root by using RT-PCR method. The opening reading frame (ORF) of MaMYB cDNA was951bp which encodes a putative protein of316amino acids and its molecule weight of35,08Kd. The alignment result of MaMYB with MYB transcription factor of other species suggested that the N-terminal of MaMYB was highly conserved and the similarity of full length was low.The analysis of phylogenic tree indicated that MaMYB was closely linked with TaRAX3and belonged to one branch, which suggested that they have a closesly genetic relationship.The analysis of MaMYB conserved domain suggested MaMYB has two SANTs and belonged to a typical R2R3-MYB transcription factor.2. The expression pattern of MaMYB under abiotic stresses of drought, high salt, low temperature and four different hormones of abscisic acid (ABA), salicy acid (SA) and jasmonic acid (JAMe) was investigated by real-time quantitative PCR. The results showed that MaMYB was greatly induced by PEG and NaCl, but had no response to cold stress, indicating that expression of MaMYB is induced by hormone and abiotic stress such as drought, salt.3. The plant expression vector of35S::MaMYB-GFP was constructed and transformed into onion epidermal cells. The result showed that MaMYB was located in the nucleus.4. The MaMYB was transformed into Arabidopsis and three transgenic lines (OE1, OE2, OE3) were obtained. We treat adult plants of three transgenic lines(OE1,OE2,OE3),35S::GFP plant expression vector (VC) and wild-type(WT) Arabidopsis with drought for22d. The result indicated the survival rates of three transgenic lines are higher than WT and VC.The roots of three transgenic lines are prevalent longer than WT and VC.The leaves is smaller and thicker than WT and VC. Compared with WT and VC, the leaves edges of transgenic lines were curled. Compared with WT and VC, the germination rate of transgenic seeds is higher after different D-mannitol concentrations treatment.5. A series of physiological indicators were measured. The result indicated that malondialdehyde (MDA) levels of WT and VC were higher than that of OE lines, which suggested that overexpression of MaMYB might result in reduced degree of oxidation of biofilm membranes and decreased accumulation of MDA.When drought for22d,the superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activity of transgenic lines are higher than that of WT and VC.These result indicated that the three enzyme activities worked together to improve the tolerance of transgenic Arabidopsis to drought stress.6. The expressions of several stess-related genes of RD22, RD29B, RAB18(dependent on ABA pathway) and RD29A, DREB2A (independent on ABA pathway) were investiaged by real-time quantitative PCR. The result indicated that the expression levels of these genes in transgenic lines were higher than that of WT and VC. These results suggested that MaMYB could improve the plants tolerance to drought stress through enhanced the expression stress expansive gene.In conclusion, MaMYB transcription factor was involved in plant tolerance to drought stress. Over-expression of MaMYB could enhance the tolerance to drought resistance by changing the plant morphology and regulating the expressions of ABA pathway-related genes.