ZmRPN1 confers quantitative variation in pollen number and boosts hybrid seed production in maize

The number of pollen grains is a critical determinant of reproductive success in seed plants and varies among species and individuals. However, in contrast with many mutant-screening studies relevant to anther and pollen development, the natural genetic basis for variations in pollen number remains largely unexplored. To address this issue, we carried out a genome-wide association study in modern maize, ultimately revealing that a large variance of the absence or presence of sequences in the promoter region of Zea mays RPN1 (ZmRPN1) alters its expression level and thereby contributes to pollen number variation. Molecular analyses showed that ZmRPN1 interacts with ZmMSP1, an ortholog of the male germline cell number regulator in Arabidopsis and rice, and facilitates ZmMSP1 localization to the plasma membrane. Importantly, ZmRPN1 dysfunction resulted in a substantial increase in pollen number, consequently boosting seed production by increasing female-male planting ratio. Together, our findings uncover a key gene controlling pollen number, and therefore modulation of ZmRPN1 expression could be efficiently used to develop elite pollinators for modern hybrid maize breeding. Overall design: RNA-seq liabraries were prepared using S3-S5 stage anthers from zmrpn1-1 and wild-type plants