Arabidopsis Ubiquitin E3 Ligase AtCHYR1 Promotes ROS Production in Plant Responses to Sugar Availability

Glucose functions as both an essential energy source and a critical signaling molecule, playing pivotal roles in regulating plant growth, development, and stress responses. Here, we report that <i>AtCHYR1</i>, a previously characterized RING-type ubiquitin E3 ligase involved in drought tolerance, also participates in glucose signaling. Exposure to high glucose levels significantly inhibits <i>AtCHYR1</i> expression, particularly in root tips, while low glucose conditions, such as osmotic stress, sugar starvation, and dark conditions, induce its expression. Importantly, analysis of <i>chyr1</i> mutants and plants overexpressing <i>AtCHYR1</i> revealed that <i>AtCHYR1</i> positively regulated the high glucose-mediated inhibition of germination and root growth, as well as starvation-induced growth retardation, through enhanced reactive oxygen species (ROS) accumulation in root tips. Additionally, transcriptional levels of glucose-activated pathogenesis-related (PR) and defense-related genes were reduced, while hypoxia-associated and ROS-inducing genes were significantly upregulated in <i>AtCHYR1</i>-overexpressing plants. Collectively, our findings provide novel insights into the role of <i>AtCHYR1</i> in plant responses to fluctuating sugar availability and its control of ROS homeostasis during seed germination and plant growth.