The Ethylene Signal Mediates Induction of GmATG8i in Soybean Plants under Starvation Stress

In higher plants, autophagy-related genes (ATGs) appear to play important roles in development, senescence, and starvation responses. Hormone signals underlying starvation-induced gene expression are involved in the expression of ATGs. An effect of starvation stress on the expression of ATGs and ethylene-related genes in young seedlings of soybean (Glycine max [L.] Merr. cv. Fukuyutaka) was analyzed. Reverse transcription-polymerase chain reaction (RT-PCR) showed that the expression levels of GmATG8i and GmATG4 increase in a starvation medium, but at a null or marginal level in a sucrose/nitrate-rich medium. The expression of GmACC synthase and GmERF are also upregulated in the starvation medium. In addition, immunoblot revealed that ethylene insensitive 3 (Ein3), an ethylene-induced transcription factor are accumulated in seedlings subjected to severe starvation stress. These results indicate that starvation stress stimulates the expression of GmATG8i and ethylene signal-related genes. Since the ethylene signal is involved in senescence and various environmental stresses, it is possible that starvation stress-induced autophagy is partly mediated by the ethylene signaling.