Cloning Apd Expression Analysis Of ABCG Transporter Family Genes In Zygophyllum Xanthoxylum Under Abiotic Stresses

Abiotic stresses such as salt,drought and heat,are important factors limiting crop and forage production.Exploring the genetic resources to improve the resistance of crop and forage is one of the effective biological ways to solve the problems.Zygophyllum xanthoxylum is a dominant xerophytic shrub species and widely distributed in northwest China and Inner Mongolia desert region.It has developed various mechanisms to adapt to stressful environments in the process of long-term evolution.Previous studies have found that it was able to absorb a great quantity of Na+ for osmotic adjustment even in low salt soils.The developed cuticle in plant surface is another important barrier of the stress resistance.As a succulent xerophyte,Z.xanthoxylum has thick cuticle.In addition,plant hormones such as abscisic acid and cytokinins,also play important roles in adaption to abiotic stresses.But the molecular mechanism of cuticle and plant hormones has not been reported in Z.xanthoxylum.In this study,taking the succulent xerophyte Z.xanthoxylum as materials,the transcriptome and expression profile of ABCG transporter genes under osmotic stress(-0.5 MPa)and 50 mM NaCl treatment were analyzed.The full length cDNA of cuticle lipid transporter gene ZxABCGll was cloned and the function of bioinformatics was analyzed.Based on real-time fluorescent quantitative PCR,the expression patterns of ZxABCG11,abscisic acid transporter gene ZxABCG25 and cytokinin transporter gene ZxABCG14 under salt treatment,osmotic and heat stress was analyzed.The main results are as follows:1.There were 31 genes of ABCG transporter family in transcriptome data of Z.xanthoxylum,including in cuticle lipid transporter genes ZxABCG11,ZxABCG15,ZxABCG31 and ZxABCG32,plant hormone transporter genes ZxABCG14 and ZxABCG25,lignin monomer transporter gene ZxABCG29,heavy metal transporter genes ZxABCG36 and ZxPDR12,and secondary metabolites transporter genes ZxPDR1 and ZxPDR9.The expression profile showed that-0.5 MPa osmotic stress induced the expression of ZxABCG11,ZxABCG11,ZxABCG25 and ZxABCG29,and 50 mM NaCl treatment can significantly induce expression of ZxABCG11,ZxABCG14 and ZxABCG29.2.The full-length cDNA of cuticle lipid transporter gene ZxABCG11 was 2416 bp long,including a predicted open reading frame of 2100 bp nucleotides,which was translated 700 amino acids.The amino acid sequence of ZxABCG11 contained characteristic motif of ABC transporters,the nucleic acid binding domain and transmembrane domains composed of six hydrophobic alpha helixes.ZxABCGll was belonged to half-size transporters in ABCG subfamily and shared 85%homology with VvABCG11.3.The expression level of ZxABCGll was significantly induced in short time such as 0.5 h under salt treatment,osmotic and heat stress.The treatment of osmotic + heat stress significantly induced the expression of Z,xABCGll,approximately 8-fold in leaf,compared to the value under control condition.The results showed that ZxABCG11 plays an important role in response to abiotic stresses.4.The expression level of ZxABCG25 in root and leaf was down-regulated under 50 mM NaCl treatment,while its expression was induced by-0.5 MPa osmotic and heat stress.The expression patterns of ZxABCG14 in root were opposite with that.We speculated that Z.xanthoxylum could increase abscisic acid concentration aboveground and reduce water loss through closure of stomata,meanwhile reduce the concentration of cytokinins in shoot and suspend growth when it was exposed to abiotic stresses.These results indicate that ZxABCGll,ZxABCG25 and ZxABCG14 could regulate the cuticular components secretion,abscisic acid and cytokinin transportation respectively,and play important roles in abiotic stresses resistance.