Stomatal movement is a crucial response of plants to drought stress. Several NAC transcription factors have been implicated in drought tolerance in maize seedlings, whereas the molecular mechanism by which they directly regulate ABA signaling components within the context of the four-cell stomatal complex remains unknown. In this study, we characterized ZmNAC16 in regulating drought resistance and stomatal closure in maize. Through phenotypic analysis of transgenic overexpression and gene-edited mutant lines, we assessed ZmNAC16 function in stomatal dynamics and drought tolerance. Overexpression of ZmNAC16 in transgenic maize resulted in increased leaf temperature, reduced stomatal conductance, decreased water loss, and enhanced drought tolerance, whereas gene-edited mutants exhibited opposite phenotypes. ZmNAC16 localized to the nucleus and acted as a transcriptional activator. Disruption of ZmNAC16 significantly downregulated key ABA signaling components, including ZmCIPK3 and ZmPP2C81, whose promoters were directly bound by ZmNAC16. Consistently, ZmNAC16 knockout mutants showed impaired ABA-induced stomatal closure, while overexpression lines displayed heightened stomatal sensitivity to ABA. Collectively, our findings demonstrate that ZmNAC16 integrates ABA signaling to regulate stomatal closure and drought tolerance in maize, positioning it as a promising target for enhancing crop resilience.

The role of phot1 in triggering hypocotyl phototropism and optimizing growth orientation has been well-characterized in Arabidopsis, whereas the role of Zmphot1 in maize remains largely unclear. Here, we show that Zmphot1 is involved in blue light-induced phototropism. Compared with Atphot1, Zmphot1 exhibited a weaker phototropic response to very low-fluence rates of blue light (< 0.01 μmol m^-2 s^-1), but stronger phototropic response to high-fluence rates of blue light (> 10 μmol m^-2 s^-1) than Atphot1. Notably, blue light exposure induced Zmphot1-green fluorescent protein (GFP), but not Atphot1-GFP, to form the aggregates in the cytoplasm of Nicotiana benthamiana cells. Furthermore, by generating the chimeric phot1 proteins, we found that the serine-threonine kinase (STK) domain at the C-terminus is responsible for a more volatile membrane association of Zmphot1. Consistently, the chimeric phot1 protein fusing the STK domain of Zmphot1 with other domains of Atphot1 responded similarly as Zmphot1 to both low and high fluence rates of blue light. Interestingly, although both Zmphot1 and Atphot1 interact with AtNPH3, Zmphot1 induced weaker dephosphorylation of NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3) than Atphot1. Together, our findings indicate that Zmphot1 and Atphot1 exhibit different photosensory function during phototropic response and that the STK domain may play a key role in determining their properties.