ATG4 MediatedPsmES4326/AvrRpt2-Induced Autophagy Dependent on Salicylic Acid inArabidopsis Thaliana

PsmES4326/AvrRpt2(AvrRpt2) was widely used as the reaction system of hypersensitive response (HR) inArabidopsis. The study showed that innpr1 (GFP-ATG8a),AvrRpt2was more effective at inducing the production of autophagosome and autophagy flux than that inGFP-ATG8a. The mRNA expression ofATG1,ATG6andATG8awere more innpr1during the early HR. Based on transcriptome data analysis, enhanced disease susceptibility 1 (EDS1) was up-regulated in wild-type (WT) but was not induced inatg4a4b(ATG4 deletion mutant) duringAvrRpt2infection. Compared with WT,atg4a4bhad higher expression ofsalicylic acid glucosyltransferase 1 (SGT1)andisochorismate synthase 1 (ICS1); but less salicylic acid (SA) in normal condition and the same level of free SA duringAvrRpt2infection. These results suggested that the consumption of free SA should be occurred inatg4a4b.AvrRpt2may trigger the activation of Toll/Interleukin-1 receptor (TIR)-nucleotide binding site (NB)-leucine rich repeat (LRR)-TIR-NB-LRR-to induce autophagy via EDS1, which was inhibited by nonexpressor of PR genes 1 (NPR1). Moreover, high expression ofNPR3inatg4a4bmay accelerate the degradation of NPR1 duringAvrRpt2infection.