In rice (Oryza sativa), caryopses located on proximal secondary branches (CSBs) have smaller grain size and poorer grain filling than those located on apical primary branches (CPBs), greatly limiting grain yield. However, the molecular mechanism responsible for developmental differences between CPBs and CSBs remains elusive. In this transcriptome-wide expression study, we identified the gene Aspartic Protease 1 (OsAsp1), which reaches an earlier and higher transcriptional peak in CPBs than in CSBs after pollination. Disruption of OsAsp1 expression in the heterozygous T-DNA line asp1-1^+/–eliminated developmental differences between CPBs and CSBs. OsAsp1 negatively regulated the transcriptional inhibitor of auxin biosynthesis, OsTAA1 transcriptional inhibition factor 1 (OsTIF1), to preserve indole-3-acetic acid (IAA) apical dominance in CPBs and CSBs. IAA also facilitated OsTIF1 translocation from the endoplasmic reticulum (ER) to the nucleus by releasing the interaction of OsTIF1 with OsAsp1 to regulate caryopses IAA levels via a feedback loop. IAA promoted transcription of OsAsp1 through MADS29 to maintain an OsAsp1 differential between CPBs and CSBs during pollination. Together, these findings provide a mechanistic explanation for the distributed auxin differential between CPBs and CSBs to regulate distinct caryopses development in different rice branches and potential targets for engineering yield improvement in crops.

在水稻（Oryza sativa）中，与近端次要分支（CPB）相比，位于近端次要分支（CSB）上的颖果具有较小的晶粒尺寸和较差的籽粒灌浆。但是，造成CPB和CSB之间发育差异的分子机制仍然难以捉摸。在这个转录组范围内的表达研究中，我们鉴定了天冬氨酸蛋白酶1（OsAsp1）基因，在授粉后CPBs中的转录峰值比CSBs中的转录峰值更高。杂合T-DNA系asp1-1 ^+/–中OsAsp1表达的破坏。消除了CPB和CSB之间的发展差异。OsAsp1生长素的生物合成，转录抑制剂负调节O的Ť AA1转录我nhibition ˚F演员1（OsTIF1），以保留吲哚-3-乙酸（IAA）在CPBS和出的CSB顶端优势。IAA还通过释放OsTIF1与OsAsp1的相互作用来调节OsTIF1从内质网（ER）到细胞核的相互作用，从而通过反馈回路调节颈突肌IAA的水平。IAA促进OsAsp1的转录通过MADS29可以在授粉期间维持CPB和CSB之间的OsAsp1差异。在一起，这些发现为CPB和CSB之间分布的生长素差异提供了机械的解释，以调节不同水稻分支中不同的颈章鱼发育以及提高作物工程产量的潜在目标。