MdHARBI1, a MdATG8i-interacting protein, plays a positive role in plant thermotolerance

Autophagy is a major degradation pathway in plants for maintaining cellular homeostasis in response to various environmental stressors. ATG8 is one of a series of autophagy-related (ATG) proteins and plays a central role in both bulk and selective autophagy. Previously, we characterized MdATG8i in apple and demonstrated that it has a positive role in apple stress resistance. Although many ATG8-interacting proteins have been found in Arabidopsis, no protein has been reported to interact with MdATG8 in apple. Here, we identified MdHARBI1 as a MdATG8i-interacting protein in apple, however, the functions of HARBI1-like proteins have not been explored in plants. Expression analysis of MdHARBI1 and pro-MdHARBI1-GUS staining of transgenic Arabidopsis exposed to high temperature demonstrated that MdHARBI1 was significantly induced by heat stress. Moreover, heat-treated MdHARBI1-trangenic tomato plants maintained higher autophagic activity, accumulated fewer ROS, and displayed stronger chlorophyll fluorescence than wild-type plants. Because these phenotypes were consistent with those displayed by MdATG8i-overexpressing apple plants under high temperature, we concluded that the MdATG8i-interacting protein MdHARBI1 plays a critical role in the basal thermotolerance of plants, mainly by influencing autophagy pathways.

Automated summary

MdHARBI1 is identified as an interacting protein of MdATG8i in apple, and is significantly induced by heat stress. It plays a critical role in the basal thermotolerance of plants by influencing autophagy pathways.