Lighting the path: how light signaling regulates stomatal movement and plant immunity

Stomata, the small pores on the surfaces of plant leaves and stems, are crucial for gas exchange and also play a role in defense against pathogens. Stomatal movement is influenced not only by surrounding light conditions but also by the presence of foliar pathogens. Certain light wavelengths such as blue or high irradiance red light cause stomatal opening, making it easier for bacteria to enter through opened stomata and causing disease progression in plants. Illumination with blue or intense red light autophosphorylates phototropin, a blue light photoreceptor protein kinase, that in turn activates a signaling cascade to open the stomata. Undoubtedly stomatal defense is a fascinating aspect of plant immunology, especially in plant-foliar pathogen interactions. During these interactions, stomata fundamentally serve as entry points for intrusive pathogens and initiate the plant defense signaling cascade. This review highlights how light-activated photoreceptors such as cryptochromes (CRYs), phytochromes (phys), and UV-receptors (UVRs) influence stomatal movement and defense signaling after foliar pathogen intrusion. It also explores the link between stomatal defense, light signaling, and plant immunity, which is vital for safeguarding crops against pathogens.