摘要Members of the ADP-ribosylation factor family,which are GTP-binding proteins,are involved in metabolite transport,cell division,and expansion.Although there has been a significant amount of research on small GTP-binding proteins,their roles and functions in regulating maize kernel size remain elusive.Here,we identified ZmArf2 as a maize ADP-ribosylation factor-like family member that is highly conserved during evolution.Maize zmarf2 mutants showed a characteristic smaller kernel size.Con-versely,ZmArf2 overexpression increased maize kernel size.Furthermore,heterologous expression of ZmArf2 dramatically elevated Arabidopsis and yeast growth by promoting cell division.Using ex-pression quantitative trait loci(eQTL)analysis,we determined that ZmArf2 expression levels in var-ious lines were mainly associated with variation at the gene locus.The promoters of ZmArf2 genes could be divided into two types,pS and pL,that were significantly associated with both ZmArf2 ex-pression levels and kernel size.In yeast-one-hybrid screening,maize Auxin Response Factor 24(ARF24)is directly bound to the ZmArf2 promoter region and negatively regulated ZmArf2 expression.Notably,the pS and pL promoter types each contained an ARF24 binding element:an auxin re-sponse element(AuxRE)in pS and an auxin response region(AuxRR)in pL,respectively.ARF24 binding affinity to AuxRR was much higher com-pared with AuxRE.Overall,our results establish that the small G-protein ZmArf2 positively regulates maize kernel size and reveals the mechanism of its expression regulation.