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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).

Autophagy plays a critical role in nutrient recycling/re-utilizing under nutrient deprivation conditions. However, the role of autophagy in soybeans has not been intensively investigated. In this study, the Autophay-related gene 7 ( ATG7 ) gene in soybeans (referred to as GmATG7 ) was silenced using a virus-induced gene silencing approach mediated by Bean pod mottle virus (BPMV). Our results showed that ATG8 proteins were highly accumulated in the dark-treated leaves of the GmATG7 -silenced plants relative to the vector control leaves (BPMV-0), which is indicative of an impaired autophagy pathway. Consistent with the impaired autophagy, the dark-treated GmATG7 -silenced leaves displayed an accelerated senescence phenotype, which was not seen on the dark-treated BPMV-0 leaves. In addition, the accumulation levels of both H 2 O 2 and salicylic acid (SA) were significantly induced in the GmATG7 -silenced plants compared with the BPMV-0 plants, indicating an activated immunity. Consistently, the GmATG7 -silenced plants were more resistant against both Pseudomonas syringae pv. glycinea ( Psg ) and Soybean mosaic virus (SMV) compared with the BPMV-0 plants. However, the activated immunity in the GmATG7 -silenced plant was not dependent upon the activation of MPK3/MPK6. Collectively, our results demonstrated that the function of Gm ATG7 is indispensable for autophagy in soybeans, and the activated immunity in the GmATG7 -silenced plant is a result of impaired autophagy.

Autophagy is a highly conserved mechanism for material degradation and recycling in eukaryote cells, and plays important roles in growth, development, stress tolerance and immune responses. ATG10 plays a key role in autophagosome formation. To understand the function of ATG10 in soybean, two homologous GmATG10 genes, namely GmATG10a and GmATG10b , were silenced simultaneously by bean pod mottle virus (BPMV) induced gene silencing. The carbon starvation induced by dark treatment and Western blotting analysis of Gm ATG8 accumulation level indicated that concurrent silencing GmATG10a/10b resulted in the impairment of autophagy in soybean; disease resistance and kinase assays demonstrated that GmATG10a/10b participated in the immune responses by negatively regulating the activation of Gm MPK3/6, indicating that GmATG10a/10b plays a negative regulatory role in immune response in soybean.

Autophagy plays a critical role in nutrient recycling and stress adaptations. However, the role of autophagy has not been extensively investigated in crop plants. In this study, soybean autophagy-related gene 2 ( GmATG2 ) was silenced, using virus-induced silencing (VIGS) mediated by Bean pod mottle virus (BPMV). An accelerated senescence phenotype was exclusively observed for the GmATG2- silenced plants under dark conditions. In addition, significantly increased accumulation of both ROS and SA as well as a significantly induced expression of the pathogenesis-related gene 1 ( PR1 ) were also observed on the leaves of the GmATG2- silenced plants, indicating an activated immune response. Consistent with this, GmATG2 -silenced plants exhibited a significantly enhanced resistance to Pseudomonas syringae pv. glycinea (Psg) relative to empty vector control plants (BPMV-0). Notably, the activated immunity of the GmATG2- silenced plants was independent of the MAPK signaling pathway. The fact that the accumulation levels of ATG8 protein and poly-ubiquitinated proteins were significantly increased in the dark-treated GmATG2- silenced plants relative to the BPMV-0 plants indicated that the autophagic degradation is compromised in the GmATG2- silenced plants. Together, our results indicated that silencing GmATG2 compromises the autophagy pathway, and the autophagy pathway is conserved in different plant species.