The 30th International Conference on Arabidopsis Research (ICAR 2019)

622 / 2019-04-24 17:19:12

Genetic Variation in GNR1 Mediates Grain Production in Rice

Oryza sativa L.,grain yield,cytokinin,transcription regulation

Plenary track > Development

Improvement of grain number per panicle is a major target in rice breeding. The molecular basis of regulating grain number consist of complex networks, although many genes and genetic pathways have been identified, the underlying molecular mechanisms controlling grain number remains largely unclear. Here, we show that GRAIN NUMBER REGULATOR 1 (GNR1), a B3 domain transcriptional repressor, acts as an essential factor for the maintenance of cytokinin homeostasis and plays an important role in controlling grain number and yield in rice. Loss-of-function of GNR1, which is highly expressed in rice reproductive meristems, reduces inflorescence meristem size and results in sparse panicle with greatly decreased grain number. We demonstrate that GNR1 directly binds to the promoter region of cytokinin degradation gene Grain number 1a/CYTOKININ OXIDASE/DEHYDROGENASE2 (Gn1a/OsCKX2), modulates the expression of Gn1a/OsCKX2 and thus regulates cytokinin homeostasis. Genetic analysis show that Gn1a/OsCKX2 acts downstream of GNR1 in control of grain number and yield. Importantly, a survey of 3,000 sequenced rice genomes reveals that a large deletion in the promoter of the GNR1 is shown to be associated with higher GNR1 expression, resulting in an increase in grain yield. Taken together, our study demonstrated that GNR1 plays pivotal roles in controlling grain number and identifying it as a promising target for improving rice grain production.