Glucose-TOR Through Transcriptional And Post-translational Modification Manners Regulates Autophagy In Arabidopsis

Like other living organisms,plants face various external conditions and cannot escape from unfriendly environments.In order to survive,plants have evolved multiple strategies to fit such constantly changing environments.Nutrient starvation is one of the most important environmental pressures,which can cause plant growth defect.Target of rapmycin(TOR)is the major nutrient receptor in Arabidopsis,which is a conserved Ser/Thr protein kinase.Recently,it has reported that TOR could regulate autophagosome formation.However,the molecular mechanisms underlining autophagy regulation by glucose-TOR(Glc-TOR)signaling remains unknown.In our study,we have used molecular biology,biochemistry,cell biology,genetic and chemical genetic approaches to study(1)how Glc-TOR signaling regulates autophagy and(2)what is the molecular mechanism of underlining autophagy regulation by Glc-TOR signaling.Firstly,we found that TOR inhibitors activated autophagy indicating that autophagy induced by glucose depletion was regulated by TOR.Secondly,through q RT-PCR analysis,we found that autophagy inhibition by Glc-TOR signaling was through expression suppression of autophagy related genes(ATGs).Thirdly,through the analysis of autophagy related mutant atg7,we found that the regulation pathway of glucose-TOR-ATGs was partially dependent on autophagy process,which can partially explain how glucose starvation regulates autophagy activation.Therefore,a specific Glucose-TOR-ATGs expression pathway exists in Arabidopsis.Besides that,we found glucose starvation can regulate autophagosome formation via post-translation modification.Under normal condition,TOR phosphorylates ATG1 and ATG13 to inhibit autophagy initiation.While during glucose starvation,TOR kinase activity is suppressed and ATG1 phosphorylates ATG13 to induce autophagy.Taken together,we revealed how Glc-TOR signal regulate autophagy initiation and the specific mechanism.Since autophagy is important for nutrient deficiency and stress tolerance,our study on autophagy initiation mechanisms may facilitate crops improvement in the future.