Abstract
SPAs (suppressors of phyA-105) are key modulators of photomorphogenesis that regulate diverse aspects of plant growth. While the role of SPA proteins in Arabidopsis photomorphogenesis is well-characterized, the functions of their maize (Zea mays L.) homologs (ZmSPAs) remain largely unexplored. Here, we show that ZmSPAs have the typical conserved domains of the SPA family and respond to different light qualities and photoperiodic treatments. Further analysis of the subcellular localization of ZmSPAs showed that ZmSPA1 and ZmSPA2 were localized to the nucleus, while ZmSPA3 and ZmSPA4 were localized to both the nucleus and the plasma membrane. The results of tissue-specific expression showed that ZmSPA1 and ZmSPA2 had the highest relative expression level in silks, while ZmSPA3 and ZmSPA4 were mainly expressed in leaves. Interestingly, overexpression of ZmSPAs in Arabidopsis promoted hypocotyl elongation in seedlings, inhibited cotyledon expansion in seedlings, and increased plant height in mature plants. The Y2H and LCI results indicate that ZmSPAs have physical interactions with ZmCOP1a, ZmCOP1b, and AtCOP1. These findings reveal the roles of ZmSPAs in regulating photomorphogenesis in Arabidopsis seedlings and plant height development in mature plants, laying a foundation for future investigations into their endogenous functions in maize.