Phylogenetic And Expression Analysis Of ROP Small GTPases In Citrus

The ROP protein family is a small Rho G protein,existed only in plants.Rho plays a important role in the regulation of pollen tube growth,root hair polarity, pathogen defensing and hormone responsing.ROP is a molecular switch of the reaction signal transduction pathway. ROP through altering with GTP or the binding of GDP to regulate its activity.The activation of ROP protein was regulated by ROPGEF, ROPGAP and ROPGDI.Sweet orange is one of the main varieties of citrus in china, with excellent quality, good flavor, appearance and aroma characteristics. Sweet orange was mostly produced in guangdong and sichuan provinces,The expression research of ROP was rare in sweet orange,and this study filled the gap.In the research, we builded the phylogenetic tree of ROP proein in sweet orange for the first time,and systematic studyed the expression of the sweet orange ROP genes in different growth stages and stress conditions.1. The evolutionary tree of sweet orange ROP proteins.The results showed that the ROP family of sweet orange included eight ROP genes: CsROP1,CsROP2,CsROP6,CsROP7A,CsROP7B,CsROP8,CsROP9and CsROP10.2. The PCR amplification of CsROP8.The primers of CsROP8were designed before the new database of sweet orange in2012, so the study did not involve the expression profile of CsROP8.3. The expression of ROP genes in sweet orange.Collected different organization, developmental stages of sweet orange fruit, eight important hormones and three kinds of pathogens infection of sweet orange seedling, extracted the RNA of all samples,and made RT-PCR and qPCR analysis.The specific expression of ROP genes were as follows:During the fruit development,the expression of almost all CsROPs reached the lowest when fruit fully ripe.The expression of CsROPl was highest in91DPA but the lowest expression in213DPA;CsROP2was highly expressed in13DPA but with the lowest expression in105DPA; CsROP6was high expressed in91DPA but with the lowest expression in13DPA;The expression level of CsROP7A and CsROP10were declining in13DPA to213DPA; The expression of CsROP9was rising in13DPA to91DPA but depressing in91DPA to213DPA,to fruit maturity (213DPA) the expression quantity reached the lowest.In different tissues of sweet orange,the expression of CsROPl,CsROP2and CsROP9were highly expressed in the reproductive branch; In bud, the expression level of CsROP6was higher than in other tissues;CsROP7A was highly expressed in undifferentiated spring shoot;In roots,CsROP7and CsROP10ere expressed with a high level.In general, the expression of the CsROP genes were easily affected by pathogen infection. In the leaves of HLB infection,the expression of CsROP genes significantly decreased.As the same time,in the leaves of CTV virus infection,the expression of CsROP genes had little change compared with normal leaf. In the leaves of Canker infection, almost all of the CsROP genes (except CsROP2) were significantly higher than that of the normal leaf.The expression of almost all CsROP genes were affected by hormones,and each CsROP had significant difference.