Grain number is a flexible trait and contributes significantly to grain yield. In rice, the zinc finger transcription factor DROUGHT AND SALT TOL-ERANCE (DST) controls grain number by directly regulating cytokinin oxidase/dehydrogenase 2 (OsCKX2) expression. Although specific upstream regulators of the DST-OsCKX2 module have been identified, the mechanism employed by DST to regulate the expression of OsCKX2 remains un-clear. Here, we demonstrate that DST-interacting protein 1 (DIP1), known as Mediator subunit OsMED25, acts as an interacting coactivator of DST. Phenotypic analyses revealed that OsMED25-RNAi and the osmed25 mutant plants exhibited enlarged panicles, with enhanced branching and spikelet number, similar to the dst mutant. Genetic analysis indicated that OsMED25 acts in the same pathway as the DST-OsCKX2 module to regulate spikelet number per panicle. Further biochemical analysis showed that OsMED25 physically interacts with DST at the promoter region of OsCKX2, and then recruits RNA polymerase II (Pol II) to activate OsCKX2 transcription. Thus, OsMED25 was involved in the communication between DST and Pol II general transcriptional machinery to regulate spikelet number. In general, our findings reveal a novel function of OsMED25 in DST-OsCKX2 modulated transcriptional regulation, thus enhancing our un-derstanding of the regulatory mechanism under-lying DST-OsCKX2-mediated spikelet number.

Lihao Lin;Minmin Du;Shuyu Li;Chuanlong Sun;Fangming Wu;Lei Deng;Qian Chen;Chuanyou Li

State Key Laboratory of Plant Genomics,National Centre for Plant Gene Research (Beijing),Institute of Genetics and Developmental Biology,The Innovative Academy of Seed Design,The Chinese Academy of Sciences,Beijing 100101,China;State Key Laboratory of Crop Biology,College of Agronomy,Shandong Agricultural University,Taian 271018,China

植物学报（英文版）

[1]Lihao Lin;Minmin Du;Shuyu Li;Chuanlong Sun;Fangming Wu;Lei Deng;Qian Chen;Chuanyou Li-.Mediator complex subunit MED25 physically interacts with DST to regulate spikelet number in rice)[J].植物学报（英文版）,2022(04):871-883

MED25,DROUGHT,ERANCE,OsCKX2,DIP1,OsMED25,osmed25,dst

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