Autophagy plays an essential role in recycling/re-utilizing nutrients and in adaptions to numerous stresses. However, the roles of autophagy in soybean have not been investigated extensively. In this study, a virus-induced gene silencing approach mediated by bean pod mottle virus (BPMV) was used to silence autophagy-related gene 5 (ATG5) genes in soybean (referred to as GmATG5). Our results showed that ATG8 proteins were massively accumulated in the dark-treated leaves of the GmATG5-silenced plants relative to the vector control plants (BPMV-0), indicating that autophagy pathway is impaired in the GmATG5-silenced plants. Consistent with the impaired autophagy, an accelerated senescence phenotype was observed on the leaves of the dark-treated GmATG5-silenced plants, which was not shown on the leaves of the dark-treated BPMV-0 plants. In addition, the accumulation levels of both reactive oxygen species (ROS) and salicylic acid (SA) were significantly induced in the GmATG5-silenced plants compared with that of the vector control plants (BPMV-0), indicating an activated immunity. Accordingly, the GmATG5-silenced plants exhibited significantly enhanced resistance against Pseudomonas syringae pv. glycinea (Psg) in comparison with the BPMV-0 plants. Nevertheless, the activated immunity observed in the GmATG5-silenced plant was independent of the activation of mitogen-activated protein kinase (MAPK).
Keywords: autophagy; immunity; mitogen-activated protein kinase (MAPK); virus-induced gene silencing.