Genome-wide Identification And Differentially Expression Analysis Of NsLTP Protein In Sugarcane In Response To Xanthomonas Albilineans Infection

Leaf scald disease is a systemic bacterial disease caused by Xanthomonas albilineans,which is one of the three major bacterial diseases of sugarcane.This disease is distributed in most worldwide sugarcane-growing countries and regions including China.This disease poses a potential threat to sugarcane production in China.In this study,in order to better understand the molecular mechanisms of sugarcane resistance to leaf scald,a comparative proteomic study was performed with two sugarcane cultivars inoculated with X.albilineans:one resistant?LCP 85-384?and one susceptible?ROC20?to leaf scald.Differentially expressed proteins?DEPs?were identitied by the iTRAQ?isobaric tags for relative and absolute quantification?approach at 0 and 48 h post-inoculation?hpi?.Subsequently,genome-wide identification and expression analysis of the non-specific lipid transporter gene family?nsLTP?in sugarcane in response to X.albilineans infection were performed.The main results were shown as follows:?1?Among 4295 identified proteins,285 DEPs were identified in two sugarcane cultivars LCP 85-384 and ROC20 during X.albilineans infection.One hundred seventy-two DEPs were identified in resistant cultivar LCP 85-384,of those DEPs,113 DEPs were upregulated and 59DEPs were downregulated.One hundred ninety-two DEPs were found in susceptible cultivar ROC20 and half of them?92?were upregulated.These significantly upregulated DEPs in LCP 85-384 were involved in metabolic pathways,the biosynthesis of secondary metabolites,and the phenylpropanoid biosynthesis pathway.Thirty-five DEPs related to resistance to leaf scald disease were identified,of which seven DEPs genes involving in different pathways were futher verified at the transcription level using q RT-PCR.Relative expression levels between protein?log₂Fold Change?and transcrip(2^–??Ct)of these genes were not significantly different according to the paired comparison T-test?p-value>0.05?.?2?Seventy-one nsLTP genes were identified in Saccharum spontaneum genome and these nsLTP genes were divided into 14 classes with the type-specific structres.In addition,these nsLTP gene promoter regions contained a large number of cis-acting elements involved in responses to biotic and abiotic stress.Furthermore,transcriptional expression patterns of nine nsLTP genes were determined by q RT-PCR assays in SES208,LCP 85-384 and ROC20 clones under X.albilineans stress.Two genes Sc LTPGb.1 and Sc LTPV.4 were significantly upregulated on LCP 85-384 and SES208,but downregulated in ROC20.Meanwhile,the four genes Sc LTPI.8,Sc LTPI.10,Sc LTPI.20 and Sc LTPGb.3 were significantly increased only in LCP 85-384.In summary,a number of DEPs and disease resistance-related pathways were identifded in sugarcane responding to X.albilineans infection using iTRAQ technology,and the gene structurure and expression patterns of nsLTP gene family were subsequently investigated in Saccharum spontaneum at genome-wide level.These results provide theoretical basises for further research on the molecular mechanism of sugarcane resistance to leaf scald disease.