Preliminary Study On The Function Of MaRALF In Musa Acuminata

Plants are in a complex and changing ecological environment and often suffer from many adversity stresses.Plant polypeptide hormones are the major signaling molecules in plants and regulate plant growth and development.RALF(rapid alkalinization factor,RALF)is a plant polypeptide hormone commonly which was found in the plant kingdom.It can increase the pH of the culture medium and regulate the growth and development of plants.In this study,a yeast cDNA expression library was constructed and the MaRALF gene was selected from the recombinant plasmids of the library.Bioinformatics,gene expression analysis,yeast complementation experiments,and prokaryotic expression proteins were used to investigate the function of the MaRALF gene.The main results are as follows:(1)RALFs are derived from a large family of genes and belong to a class of small-molecule signal peptide proteins that are modified by the processing of precursor proteins.The N-terminal sequence of most precursor proteins is not conserved,while the C-terminal is more conserved and contains YIXY,YXRGC motifs,and two disulfide bonds are formed by four cysteine residues.(2)The results of gene expression showed that MaRALF can participate in the induction of hormones(GA,ABA),oxidative stress(methyl spermatozoa),osmotic stress(mannitol)and low temperature(4°C)that can be used as a stress response gene responsing to environmental stress.MaRALF gene expression levels under different stress treatments have different expressions,including ABA,heavy metal Cd stress and other induction which can make MaRALF gene expression in leaves upregulated,but its expression in the root is downregulated.In addition,expression of the gene responsing to the heavy metal,high salt stress is greater than the temperature expression.It shows that MaRALF may be involved in regulating the growth and development of bananas.It was shown that MaRALF may act as a defensive gene and participate in the response of bananas to stress in response to environmental stress.(3)In this experiment,the prokaryotic protein expression vector GST-MaRALF was constructed and transformed into E.coli BL21 and the recombinant protein was induced with a molecular weight of approximately 38 kDa.The recombinant GST-MaRALF protein was added to the roots of Arabidopsis thaliana seedlings grown for 7 days wihch detect the effect of GST-MaRALF recombinant protein on Arabidopsis root length.The results showed that the recombinant protein can significantly inhibit the root length of Arabidopsis seedlings,indicating that the obtained recombinant protein has the function of inhibiting the length of Arabidopsis roots and can participate in the regulation of plant growth and development.At the same time,the induction of GST-MaRALF recombinant protein in E.coli BL21 to cope with heavy metal Cd,high salt stress also showed a certain degree of tolerance.(4)The result of yeast functional complementation test showed that the MaRALF has certain antioxidation and resistance to heavy metal Cd which can increase antioxidant and cadmium sensitivity in oxidation-sensitive S.cerevisiae strain Δskn7 and Saccharomyces cerevisiae strain Δycf1 resistantcing to heavy metal Cd.