Functional Analysis Of SbSTAR1 And SbSTAR2 In Sweet Sorghum (Sorghum Bicolor L.) Under Aluminum Stress

Acidic soil accounts for about 30%of the world's land area,and accounts for about 40-50%of the world's potential arable land.About 22.7%of the national lands are acidic soils.Al toxicity is a major limiting factor for crop yield on acidic soils.Under acidic conditions,the concentration of Al³⁺ions in the rhizosphere soil solution gradually increased.Micromolar Al³⁺ions can inhibit root elongation and limit root absorption of mineral nutrients and moisture.During long-time growth and evolution,plants have formed many Al-tolerance mechanisms.And they are mainly summarized in two major categories,namely external exclusion mechanisms and internal tolerance mechanisms.A variety of Al-tolerant genes are involved in Al tolerance in plants,including organic acid transporters,ABC transporters,metal ion transporters,aquaporins and transcription factors.Under Al stress,OsSTAR1 and OsSTAR2 can interact with each other,forming an ABC transporter.It is responsible for transporting UDP-Glc from the cytosol into the vesicles.UDP-Glc then is released from the vesicles to the apoplast by exocytosis and used to modify the cell walls to modify the sites for aluminum binding,resulting in aluminum tolerance in rice.The study of Al resistance is relatively poor in sweet sorghum.And the homologous proteins of STAR1 and STAR2 in Sweet sorghum has not been reported.In this study,the sensitive cultivar POT?POTCHETSTRM?and the tolerant cultivar ROMA were used as materials.I analyze the functions of SbSTAR1 and SbSTAR2 through bioinformatics analysis,subcellular localization,protein interaction analysis,transcriptional regulation analysis,expression pattern analysis,and phenotype analysis.The results are as follows:1.I blasted in Sweet sorghum database with the amino acid sequence of OsSTAR1 and OsSTAR2.There were 1 homologous protein of OsSTAR1 and 2homologous proteins of OsSTAR2 in sweet sorghum.Sequence alignment and phylogenic tree analysis showed that the homology between SbSTAR1 and OsSTAR1,SbSTAR2a,SbSTAR2b and OsSTAR2 was extremely high.The results of subcellular localization showed that the three protein SbSTAR1,SbSTAR2a and SbSTAR2b were expressed in the whole cell.2.Yeast Two-hybrid?-galactosidase activity assay and Yeast Two-hybrid validation showed that SbSTAR1 can not interact with SbSTAR2a or SbSTAR2b.The transcriptional regulation analysis showed that the expression of SbSTAR1,SbSTAR2a and SbSTAR2b can all be regulared by SbSTOP1.3.Expression pattern analysis showed that the transcriptional expression of SbSTAR1,SbSTAR2a and SbSTAR2b were induced by not only aluminum but also cadmium.Under aluminum stress,The expression of SbSTAR1,SbSTAR2a and SbSTAR2b was the highest in 1-3cm of roots.But the degree of induction by aluminum was greatest in 0-1cm of root tips.4.Phenotypic assay with SbSTAR1,SbSTAR2a,and SbSTAR2b heterologously expressed in Arabidopsis wild type indicated that overexpressed SbSTAR1,SbSTAR2a,and SbSTAR2b in Arabidopsis wild type could increase Al tolerance.