J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (7): 1767-1781.DOI: 10.1111/jipb.13473

• Molecular Physiology • Previous Articles     Next Articles

An ARF24-ZmArf2 module influences kernel size in different maize haplotypes

Jie Gao1†, Long Zhang1†, Haonan Du1, Yongbin Dong1, Sihan Zhen2, Chen Wang1, Qilei Wang1, Jingyu Yang1, Paifeng Zhang1, Xu Zheng1* and Yuling Li1*   

  1. 1. State Key Laboratory of Wheat and Maize Crop Science, Henan Maize Engineering Technology Joint Center, College of Agronomy, and Center for Crop Genome Engineering, Longzi Lake Campus, Henan Agricultural University, Zhengzhou 450046, China;
    2. Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China
    These authors contributed equally to this article.
    *Correspondences: Yuling Li (yuling_li@126.com, Dr. Li is fully responsible for the distributions of the materials associated with this article); Xu Zheng (zhengxu@henau.edu.cn)
  • Received:2022-07-18 Accepted:2023-02-28 Online:2023-03-03 Published:2023-07-01

Abstract: 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. Conversely, ZmArf2 overexpression increased maize kernel size. Furthermore, heterologous expression of ZmArf2 dramatically elevated Arabidopsis and yeast growth by promoting cell division. Using expression quantitative trait loci (eQTL) analysis, we determined that ZmArf2 expression levels in various 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 expression 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 response element (AuxRE) in pS and an auxin response region (AuxRR) in pL, respectively. ARF24 binding affinity to AuxRR was much higher compared 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.

Key words: ARF24, auxin response, maize kernel, ZmArf2

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