Study Of Abiotic(Drought And Copper) Stress Tolerance Mechanism And Analysis Of Autophagy-related Genes In Grapevine Through Modern Molecular Approaches

Grapevine(Vitis vinifera L.)is a vital and extensively grown fruit crop,which is threatened by abiotic stresses worldwide.Drought and Copper(Cu)stress are ubiquitous abiotic stress factors,which severely affect growth and development,thus a major constraint for viticulture production globally.Therefore,it is necessary to screen the grapevine genetic resources for potential to counter and adapt the stressful environment.RNA-sequencing(RNA-seq)analysis was executed using cDNA libraries constructed from both drought-stress and control plants.Results revealed 12,451 differentially expressed genes(DEGs),out of which 8,021 DEGs were up-regulated,and 4,430 DEGs were down-regulated.Moreover,the decline in stomatal conductance inhibit the photosynthetic activity and CO2 assimilation,which was in line with transcriptomic analysis.Reactive oxygen species,including stress enzymes,their related proteins,and secondary metabolites were also activated to counter the drought severity.Likewise,various hormones,such as abscisic acid(ABA),gibberellin(GA),auxin(AUX),and brassinosteroids(BRs)involved in the survival of grapevine and induced in response to drought stress.Drought stress inhibit the photosynthetic process,which affected the synthesis of reducing sugars(glucose and fructose)contrary to sorbitol contents,which accumulated in drought-responsive grapevine leaves.Moreover,the alleviated level of oxidative stress marker(malondialdehyde,MDA)gives rise to superoxide radicals(O2·-)and hydrogen peroxide(H2O2),while the antioxidative scavenging system also activated to counter the reactive oxygen species(ROS).The elucidation of calcium(Caz+)and mitogen-activated protein kinase(MAPK)pathways revealed that the genes encoding pathogen-associated molecular pattern(PAMP)triggered immunity(PTI),including calcium signals,protein phosphatase 2C(PP2C),calcineurin B-like proteins(CBL),MAPKs,and phosphorylation(FLS2 and MEKK1)cascades were up-regulated in response to drought stress.Several genes related to plant-pathogen interaction pathway(RPM1,PBS1,RPS5,RIN4,MIN7,PR1,and WRKYs)were also found up-regulated to induce defense responses in grapevine against drought stress.Genome-wide analysis was performed to identify Vitis vinifera autophagy-related genes(VvARGs),and 35 VvARGs were detected.A gene family analysis revealed thattandem and segmental duplication events played significant roles in the VvARG gene family expansion.Also,there was more intense signature of purifying selection for the comparison between grape and rice than between grape and Arabidopsis.In response to copper treatment,both the autophagosome number and malondialdehyde concentration increased during the initial 4h post-treatment and reached maximal values at 24h.An expression analysis indicated that most VvARGs responded to copper stress at 4h post-treatment,and some VvARGs(e.g.,VvATG6,VvATG8i,and VvATG18h)exhibited responses to abiotic stresses.This study provides some basic new information about the selection of candidate genes involve in the grapevine defense response under drought stress and provide an overview of the ARGs in grapevine and indicate multiple functions of autophagy in fruit development and abiotic stresses in grapevine.Furthermore,functional analysis of individual genes can provide deeper insight for their key role to provide defense response in grapevine plants against abiotic stress environments.