The C₂H₂-type zinc finger transcription factor ZmDi19-7 regulates plant height and organ size by promoting cell size in maize

The drought-induced protein 19 (Di19) gene family encodes a Cys2/His2 zinc-finger protein implicated in responses to diverse plant stressors. To date, potential roles of these proteins as transcription factors remain largely elusive in maize. Here, we show that ZmDi19-7 gene exerts pivotal functions in regulation of plant height and organ growth by modulating the cell size in maize. ZmDi19-7 physically interacts with ubiquitin receptor protein ZmDAR1b, which is indispensable in ubiquitination of ZmDi19-7 and affects its protein stability. Further genetic analysis demonstrated that ZmDAR1b act in a common pathway with ZmDi19-7 to regulate cell size in maize. ZmDi19-7, severing as a transcriptional factor, is significantly enriched in conserved DiBS element in the promoter region of ZmHSP22, ZmHSP18c, ZmSAUR25, ZmSAUR55, ZmSAUR7 and ZmXTH23 and orchestrates the expression of these genes involving in auxin-mediated cell expansion and protein processing in the endoplasmic reticulum. Thus, our findings demonstrate that ZmDi19-7 is an important newfound component of the ubiquitin-proteasome pathway in regulation of plant height and organ size in maize. These discoveries highlight potential targets for the genetic improvement of maize in the future.