Maize WRKY28 interacts with the DELLA protein D8 to affect skotomorphogenesis and participates in the regulation of shade avoidance and plant architecture

Competition for light from neighboring vegetation can trigger the shade-avoidance response (SAR) in plants, which is detrimental to their yield. The molecular mechanisms regulating SAR are well established in Arabidopsis, and some regulators of skotomorphogenesis have been found to be involved in the regulation of the SAR and plant architecture. However, the role of WRKY transcription factors in this process has rarely been reported, especially in maize (Zea mays). Here, we report that maize Zmwrky28 mutants exhibit shorter mesocotyls in etiolated seedlings. Molecular and biochemical analyses demonstrate that ZmWRKY28 directly binds to the promoter regions of the Small Auxin Up RNA (SAUR) gene ZmSAUR54 and the Phytochrome-Interacting Factor (PIF) gene ZmPIF4.1 to activate their expression. In addition, the maize DELLA protein Dwarf Plant8 (D8) interacts with ZmWRKY28 in the nucleus to inhibit its transcriptional activation activity. We also show that ZmWRKY28 participates in the regulation of the SAR, plant height, and leaf rolling and erectness in maize. Taken together, our results reveal that ZmWRKY28 is involved in GA-mediated skotomorphogenic development and can be used as a potential target to regulate SAR for breeding of high-density-tolerant cultivars.