Spatially Resolved ABA Signalling Reveals Dual Role in Tomato Yield.

Abscisic acid (ABA) is a central hormonal regulator of plant adaptation to stress and developmental progression. However, its contribution to agronomic traits such as yield remains unclear due to the pleiotropic nature of ABA signalling. To disentangle distinct physiological functions of ABA, we employed a receptor-specific gain-of-function strategy in tomato, activating downstream signalling independently of endogenous hormone levels in an ABA-deficient background. This approach revealed two separable ABA-responsive modules that contribute to yield formation: one enhancing drought resilience through improved stomatal regulation, and another restoring reproductive success by promoting pollen viability and anther development. These physiological responses, governed by spatially distinct sites of ABA action, partially mitigated the yield penalties associated with ABA deficiency, although neither alone was sufficient to fully restore productivity. Our findings establish a dual functional framework by which ABA signalling coordinates water conservation with reproductive fitness, providing mechanistic insight into how hormone signalling integrates stress adaptation with crop yield. This modular understanding lays the foundation for targeted manipulation of ABA pathways to improve agricultural resilience under climate stress.