Cloning And Function Of IbHMGR Gene In Sweet Potato(Ipomoea Batatas(L.)Lam)

Sweet Potato(Ipomoea batatas(L.)Lam)is one of the important food crops in China,which has the characteristics of high yield,poor resistance and high nutrient content.However,in some saline areas,the yield and quality of sweet potatoes are greatly affected.In this experiment,In order to know the physiological response of Sweet Potato to salt stress,different genotypes of sweet potato seedlings(Jishu 26 and Nonglin 54)were used to study their physiological and biochemical characteristics,such as photosynthetic rate,ABA content,osmotic adjustment substance content and antioxidant enzyme activity under 150 mM NaCl stress.The complete cDNA sequence and genome sequence of IbHMGR gene,which was differentially expressed under salt stress,were identified and cloned by high throughput sequencing analysis,and the corresponding overexpression vectors were constructed A preliminary study of the function of the gene.It turns out that:(1)With the increase of salt stress time,the photosynthetic rate and stomatal conductance in the seedlings of two sweet potato varieties decreased gradually,the activity of antioxidant enzymes such as ABA content,POD and SOD increased at first,then decreased,and the content of Malondialdehyde increased continuously;The contents of soluble protein,soluble sugar,proline and other osmotic regulators increased at first and then decreased,and the contents of Na+ increased continuously from 0.5 to 12 hours after salt treatment.On the whole,the change trend of physiological indexes of two sweet potato varieties was basically the same,but the change range was obviously different;with the increase of stress time,the activities of antioxidant enzymes,osmotic regulators in salt-tolerant variety Jishu 26,the change range of ABA content was significantly higher than that of the salt-sensitive variety Nonglin 54,which may be one of the main reasons for its high salt tolerance.In salt-sensitive variety Nonglin 54,the decreasing range of chlorophyll content,photosynthetic rate and the increasing range of MDA content were significantly higher than that of salt-tolerant variety Jishu 26.(2)Through the comparative analysis of transcriptome data of two different genotypes of sweet potato,a total of 24,591 differential expression genes and 6 classes of transcription factors(bZIP,TCP,CBF,MYB,FYVE,SRF)related to salt tolerance were found.Through Go function classification and Pathway analysis,it was found that the significantly enriched differential genes are involved in 48 pathways,which are divided into 74 GO-term and exercise different functions.(3)According to transcriptome data,the complete cDNA sequence and genome sequence of’IbHMGR gene were cloned from sweet potato.Using bioinformatics analysis method,the nucleotide sequence,two-stage structure,three-stage structure and functional domain of IbHMGR gene were analyzed,and the results showed that the coding region of IbHMGR gene was 1692bp and it encoded a polypeptide containing 563 amino acids.Through the analysis of the full length sequence of its genome,it is shown that the IbHMGR gene has no introns.The over-expression vector of IbHMGR gene was constructed,transferred to Agrobacterium,and then infected with sweet potato embryo callus by Agrobacterium,positive transgenic callus was obtained.(4)The expression pattern of IbHMGR gene in sweet potato was studied by qRT-PCR.The results showed that the expression of IbHMGR gene was highest in stem root,then in old leaves and lowest in shoot apex under normal conditions.Using20%PEG6000 and 1 OOuM exogenous ABA treatment of sweet potato seedlings,it was found that the IbHMGR gene was induced by drought and exogenous ABA,and the relative expression in different tissue parts showed leaf>root>stem.