The Responses of Wheat Autophagy and ATG8 Family Genes to Biotic and Abiotic Stresses

Abstract

Autophagy is a conserved self-degradation process in eukaryotic cells. The execution of autophagy relies on a number of AuTophaGy-related (ATG) factors including ATG8 which is encoded in higher eukaryotes by a family of genes. A protective role of autophagy against environmental stresses has been described in several plant species but not in wheat (Triticum aestivum L.), and information on the functional differentiation of ATG8 family is lacking. In this study, we investigated the responses of wheat autophagy and ATG8 family genes to different stresses. In wheat seedlings and within 48 h of salt/drought stress or 4 days of nitrogen starvation stress, the autophagic activity of leaf tissues was activated by these three abiotic stresses and that of root tissues enhanced by drought and nitrogen starvation. This activated or enhanced autophagic activity was supported by up-regulated expression levels of ATG8s. Wheat ATG8s also responded to infection by the powdery mildew causal fungus, and their expression was inhibited in susceptible seedlings while repeatedly up-regulated in resistant seedlings during the early stage of pathogen infection. A comparison among the ATG8 family showed that different ATG8s had similar stress-regulated expression patterns and that several ATG8s were more sensitive to specific stresses. Collectively, these results suggest that the ATG8-requiring autophagy process is involved in wheat responses to stresses and that different ATG8s are commonly involved but have unequal significance in wheat response to specific stresses.