LAUSR

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 (Arabidopsis thaliana), and some skotomorphogenesis regulators 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 is rarely reported, especially in maize (Zea mays L.). Here, we report that maize zmwrky28 mutants exhibited shorter mesocotyls in etiolated seedlings. Molecular and biochemical analyses demonstrated that ZmWRKY28 directly binds to the promoter region of a SMALL AUXIN UP RNA (SAUR) gene ZmSAUR54 and a PHYTOCHROME-INTERACTING FACTORPIF 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. Our results also showed that ZmWRKY28 participates in the regulation of the SAR, plant height, leaf rolling and erectness in maize. Taken together, these 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.