Abstract
Cyclic adenosine 3′,5′-monophosphate (cyclic AMP; cAMP) has emerged as a bona fide signalling molecule in plants. Although its regulatory roles in diverse cellular processes are increasingly recognised, the transient nature of cAMP signalling has limited our understanding of its systemic functions at the whole-plant level. In this study, we engineered Arabidopsis thaliana plants to constitutively express adenylate cyclase (AC) activity, thereby enabling sustained elevation of endogenous cAMP levels. The AC transgenic lines exhibited a 1.3- to 1.8-fold increase in endogenous cAMP content relative to wild-type plants. Elevated cAMP promoted accelerated growth and developmental progression, enhanced photosynthetic performance, increased cellular metabolic activity, and improved productivity, as evidenced by 13–14% greater plant height, 12–17% higher 1000-seed weight, and 36–41% greater seed yield per plant. However, these growth advantages were accompanied by increased susceptibility to salinity stress, pathogen infection, and exogenous ethylene treatment compared with wild-type plants. Collectively, our findings establish cAMP as a central regulator of plant physiology that coordinates growth, development, metabolism, and stress responsiveness. While sustained elevation of endogenous cAMP enhances plant growth and productivity, it also increases sensitivity to environmental stimuli, highlighting the importance of precise spatiotemporal regulation of cAMP signalling in maintaining optimal plant performance.