antagonistic actions of hlhbhlh proteins are involved in grain length and weight in rice敌对行动hlhbhlh蛋白质参与粮食长度和重量的大米.pdf

Antagonistic Actions of HLH/bHLH Proteins Are Involved in Grain Length and Weight in Rice Dany Heang, Hidenori Sassa* Graduate School of Horticulture, Chiba University, Chiba, Japan Abstract Grain size is a major yield component in rice, and partly controlled by the sizes of the lemma and palea. Molecular mechanisms controlling the sizes of these organs largely remain unknown. In this study, we show that an antagonistic pair of basic helix-loop-helix (bHLH) proteins is involved in determining rice grain length by controlling cell length in the lemma/ palea. Overexpression of an atypical bHLH, named POSITIVE REGULATOR OF GRAIN LENGTH 1 (PGL1), in lemma/palea increased grain length and weight in transgenic rice. PGL1 is an atypical non-DNA-binding bHLH and assumed to function as an inhibitor of a typical DNA-binding bHLH through heterodimerization. We identified the interaction partner of PGL1 and named it ANTAGONIST OF PGL1 (APG). PGL1 and APG interacted in vivo and localized in the nucleus. As expected, silencing of APG produced the same phenotype as overexpression of PGL1, suggesting antagonistic roles for the two genes. Transcription of two known grain-length-related genes, GS3 and SRS3, was largely unaffected in the PGL1-overexpressing and APG-silenced plants. Observation of the inner epidermal cells of lemma revealed that are caused by increased cell length. PGL1-APG represents a new grain length and weight-controlling pathway in which APG is a negative regulator whose function is inhibited by PGL1. Citation: Heang D, Sassa H (2012) Antagonistic Actions of HLH/bHLH Proteins Are Involved in Grain Length and Weight in Rice. PLoS ONE 7(2): e31325. doi:10.1371/journal.pone.0031325 Editor: Keqiang Wu, National Taiwan University, Taiwan