Interplay of light and abscisic acid signaling to modulate plant development

Abstract Exogenous light cues and the phytohormone abscisic acid (ABA) regulate several aspects of plant growth and development. In recent years, the role of crosstalk between the light and ABA signaling pathways in regulating different physiological processes has become increasingly evident. This includes regulation of germination and early seedling development, control of stomatal development and conductance, growth, and development of roots, buds, and branches, and regulation of flowering. Light and ABA signaling cascades have various convergence points at both DNA and protein levels. The molecular crosstalk involves several light signaling factors such as HY5, COP1, PIFs, and BBXs that integrate with ABA signaling components such as the PYL receptors and ABI5. In particular, ABI5 and PIF4 promoters are key ‘hotspots’ for integrating these two pathways. Plants acquired both light and ABA signaling pathways before they colonized land almost 500 million years ago. In this review, we discuss recent advances in the interplay of light and ABA signaling regulating plant development and provide an overview of the evolution of these two pathways.