Grain quality is an important agricultural trait that is mainly determined by grain size and composition. Here, we characterize the role of the rice transcription factor (TF) SALT-RESPONSIVE ERF1 (SERF1) during grain development. Through genome-wide expression profiling and chromatin immunoprecipitation, we found that SERF1 directly regulates RICE PROLAMIN-BOX BINDING FACTOR (RPBF), a TF that functions as a positive regulator of grain filling. Loss of SERF1 enhances RPBF expression resulting in larger grains with increased starch content, while SERF1 overexpression represses RPBF resulting in smaller grains. Consistently, during grain filling, starch biosynthesis genes such as GRANULE-BOUND STARCH SYNTHASEI (GBSSI), STARCH SYNTHASEI (SSI), SSIIIa, and ADP-GLUCOSE PYROPHOSPHORYLASE LARGE SUBUNIT2 (AGPL2) are up-regulated in SERF1 knockout grains. Moreover, SERF1 is a direct upstream regulator of GBSSI. In addition, SERF1 negatively regulates germination by controlling RPBF expression, which mediates the gibberellic acid (GA)-induced expression of RICE AMYLASE1A (RAmy1A). Loss of SERF1 results in more rapid seedling establishment, while SERF1 overexpression has the opposite effect. Our study reveals that SERF1 represents a negative regulator of grain filling and seedling establishment by timing the expression of RPBF.
谷粒品質(zhì)是一個重要的農(nóng)藝性狀，它決定于籽粒大小和營養(yǎng)組分。本文報道了水稻籽粒發(fā)育過程中轉(zhuǎn)錄因子SALT-RESPONSIVE ERF1（SERF1）的作用。通過全基因組表達(dá)譜分析和染色質(zhì)免疫沉淀，我們發(fā)現(xiàn)SERF1直接調(diào)控RICE PROLAMIN-BOX BINDING FACTOR（RPBF），RPBF是一個調(diào)控籽粒灌漿的正調(diào)控因子。SERF1功能缺失會使RPBF表達(dá)量提高，導(dǎo)致籽粒增大，淀粉含量提高；而SERF1過量表達(dá)會使RPBF表達(dá)量下降，導(dǎo)致籽粒減小。與此一致，在籽粒灌漿過程中，淀粉生物合成基因如GRANULEBOUND STARCH SYNTHASEI (GBSSI)、STARCH SYNTHASEI (SSI)、SSIIIa和ADP-GLUCOSE PYROPHOSPHORYLASE LARGE SUBUNIT2 (AGPL2)在SERF1敲除系的籽粒中表達(dá)上調(diào)。此外，SERF1位于GBSSI上游直接調(diào)控其表達(dá)，而且，SERF1通過調(diào)控RPBF表達(dá)負(fù)調(diào)控種子萌發(fā)，從而介導(dǎo)了赤霉素誘導(dǎo)的RICE AMYLASE1A (RAmy1A)基因表達(dá)。SERF1功能缺失導(dǎo)致幼苗的快速生長，而SERF1過量表達(dá)具有相反的效應(yīng)。這些結(jié)果表明SERF1通過影響RPBF表達(dá)負(fù)向調(diào)控籽粒灌漿和幼苗建成。