Arabidopsis RGLG1/2 regulate flowering time under different soil moisture conditions by affecting the protein stability of TOE1/2

Abstract

• Drought constitutes a significant environmental factor influencing the growth and development of plants. Consequently, terrestrial plants have evolved a range of strategies to mitigate the adverse effects of soil water deficit. One such strategy, known as drought escape, involves the acceleration of flowering under drought, thereby enabling plants to complete their life cycle rapidly. However, the molecular mechanisms underlying this adaptive response remain largely unclear.
• Using genetic, molecular, and biochemical techniques, we demonstrated that the AP2 family proteins TARGET OF EAT 1/2 (TOE1/2) are essential for the drought escape response in Arabidopsis, with a significant reduction in their protein stability observed during this process.
• Our findings indicate that the RING-type E3 ubiquitin ligases RING DOMAIN LIGASE 1/2 (RGLG1/2) interact with TOE1/2 and facilitate their degradation within the nucleus. Under water deficit conditions, there is increased expression of RGLG1/2, and their protein products translocate to the nucleus to ubiquitinate and degrade TOE1/2, thereby enhancing the drought escape response.
• Furthermore, the loss of TOE1/2 in drought conditions directly results in a reduction of drought resistance in plants, suggesting that drought escape is a high-risk behaviour for plants and that the RGLG1/2–TOE1/2 signalling cascade may serve as a central regulatory mechanism governing the trade-off between drought escape and drought tolerance in plants.