Fine Mapping of RppP25, a Southern Rust Resistance Gene in Maize

Southern rust （Puccinia polysora Underw.） is a major disease that can cause severe yield losses in maize （Zea mays L.）. In our previous study, a major gene RppP25 that confers resistance to southern rust was identified in inbred line P25. Here, we report the fine mapping and candidate gene analysis of RppP25 from the near-isogenic line F939, which harbors RppP25 in the genetic background of the susceptible inbred line F349. The inheritance of resistance to southern rust was investigated in the BC1F1 and BC3F1 populations, which were derived from a cross between F939 and F349 （as the recurrent parent）. The 1：1 segregation ratio of resistance to susceptible plants in these two populations indicated that the resistance is controlled by a single dominant gene. Ten markers, including three simple sequence repeat （SSR） markers and seven insertion/deletion （InDel） markers, were developed in the RppP25 region. RppP25 was delimited to an interval between P091 and M271, with an estimated length of 40 kb based on the physical map of B73. In this region, a candidate gene was identified that was predicted to encode a putative nucleotide-binding site leucine-rich repeat （NBS-LRR） protein. Two co-segregated markers will aid in pyramiding diverse southern rust resistance alleles into elite materials, and thereby improve southern rust resistance worldwide.

Overexpression of the maize GRF10, an endogenous truncated growth-regulating factor protein, leads to reduction in leaf size and plant height

It has long been thought that growth‐regulating factors（GRFs） gene family members act as transcriptional activators to play important roles in multiple plant developmental processes. However, the recent characterization of Arabidopsis GRF7 showed that it functions as a transcriptional repressor of osmotic stress‐responsive genes. This highlights the complex and diverse mechanisms by which different GRF members use to take action. In this study, the maize（Zea mays L.） GRF10 was functionally characterized to improve this concept. The deduced ZmGRF10 protein retains the N‐terminal QLQ and WRC domains, the characteristic regions as protein‐interacting and DNA‐binding domains, respectively. However,it lacks nearly the entire C‐terminal domain, the regions executing transactivation activity. Consistently, ZmGRF10 protein maintains the ability to interact with GRF‐interacting factors（GIFs） proteins, but lacks transactivation activity.Overexpression of ZmGRF10 in maize led to a reduction in leaf size and plant height through decreasing cell proliferation,whereas the yield‐related traits were not affected. Transcriptome analysis revealed that multiple biological pathways were affected by ZmGRF10 overexpression, including a few transcriptional regulatory genes, which have been demonstrated to have important roles in controlling plant growth and development. We propose that ZmGRF10 aids in fine‐tuning the homeostasis of the GRF‐GIF complex in the regulation of cell proliferation.