Identification Of The CcTLP Family Of Carya Cathayensis And Its Function In Pathogen Response

Hickory(Carya cathayensis Sarg.)nut is rich in nutrients with strong economic benefit,which has become the main income source of forest farmers.However,some diseases,like trunk canker and root-rot disease,come in the process of planting.Thaumatin-like proteins(TLPs)are vital proteins involved in the complex defense process of plant pathogens,but the function in hickory remains unknown.Using multiple techniques,the function of this gene family was studied.The main results were follows:(1)The TLP family in hickory contains 40 genes and phylogenetically grouped into three subfamilies.The sequence of CcTLPs had a conservative pattern,including eight stable disulfide bonds,G-X-[GF]-X-C-X-T-[GA]-D-C-X(1,2)-G-X-(2,3)-C and REDDD structure.(2)The expression level of nine CcTLP genes(CcTLP28,CcTLP29,CcTLP30,CcTLP31,CcTLP32,CcTLP33,CcTLP37,CcTLP38,CcTLP39)from the same clade with AT1G75040,AT1G75030,and AT1G18250 were analyzed using qRT-PCR.After application of salicylate(SA),methyl jasmonate(MeJA),and ethephon(ETH)onto hickory leaves,these genes presented different expression patterns,showing that most of TLP genes were rapidly upregulated by SA,while the response to MeJA and ETH treatment were inconsistent,and the up-regulation trend were not significant.(3)After inoculating the stems of Carya cathayensis with Botryosphaeria dothidea,black spots appeared at the inoculation site.Nine genes showed different expression patterns,seven of them were significantly upregulated.The JA and H2 JA contents were greatly increased after 7 days post inoculation(dpi),while JA-Phe,SA and SAG contents were significantly decreased.And the expression levels of SArelated genes were both upregulated at the early stage,while the genes in JA pathway had different expression patterns,nevertheless the expression values of JA negative regulator,JZA1,JAZ2 and JAZ3 were minimum at 7 dpi.(4)Subcellular localization analysis showed that the nine genes were to be located at the plasma membrane and cytoplasm.(5)CcTLP30 transgenic Arabidopsis thaliana lines enhanced resistance to pst DC3000 and B.dothidea,and decreased resistance to Botrytis cinerea.It also was found that the ROS accumulation level were higher in transgenic A.thaliana lines after inoculation with pathogens.In conclusion,there were forty CcTLP genes in hickory and nine of them had different responses to SA,JA,and ETH treatments as well as B.dothidea inoculation.It was also speculated that some CcTLP genes expression may be regulated by SA signal to mediate disease resistance against B.dothidea at early stage,while at the later stage,it may be mainly through JA signal.ROS may play an important role in CcTLP30 transgenic Arabidopsis thaliana lines when they were attacked with pathogens.With these studies,the disease resistance of the CcTLP family members in hickory were preliminary studied,providing guidance for future molecular breeding improvement of hickory.