内蒙古大学齐艳华小组揭示了OsbHLH166-OsABCB4模块通过改变生长素外排调节颗粒长度和重量。相关论文于2025年4月28日发表在《科学通报》杂志上。

晶粒尺寸是决定籽粒重和产量的关键因素之一。

然而，生长素信号如何调节水稻的晶粒大小仍是未知的。在重组自交系9311和Nipponbare （NIP）中鉴定出一个籽粒长度的数量性状qGL1，并将其定位到编码ATP Binding Cassette B （ABCB）亚家族成员的OsABCB4基因上。与NIP相比，OsABCB4功能缺失导致水稻籽粒变长、变重，而OsABCB4过表达导致水稻籽粒变短、变轻，显示出对水稻籽粒长度和重量的负调控。

对3024个水稻基因组的单倍型分析表明，OsABCB4基因中SNP25和SNP55与水稻籽粒长度相关。从酵母单杂交文库中筛选到一种碱性螺旋-环-螺旋转录因子OsbHLH166，经电泳迁移率转移试验和酵母单杂交验证，证实其可直接结合OsABCB4的启动子，双荧光素酶报告基因试验证实其可激活OsABCB4的表达。与OsABCB4匹配的OsbHLH166在茎和颖片中的表达量均较高。OsABCB4在质膜上亚细胞定位，证实其为生长素外排转运体。

组织学分析、IAA含量测定和DR5:GUS活性分析表明，OsbHLH166和OsABCB4通过调控水稻籽粒发育过程中颖质细胞的增殖和生长素含量，以及改变GL7、GS2、TGW3和GS3基因的表达来调控籽粒长度。这一新发现的OsbHLH166-OsABCB4模块，揭示了生长素调控籽粒大小和重量的分子机制，为籽粒型分子设计育种提供了新的基因抗性。

附：英文原文

Title: The OsbHLH166-OsABCB4 module regulates grain length and weight via altering auxin efflux

Author: Zhenyu Gao b, Qian Qian b c, Yanhua Qi a

Issue&Volume: 2025/04/28

Abstract: Grain size is one of the key factors determining grain weight and yield. However, it remains largely unknown how the auxin signal regulates grain size in rice. Here, a quantitative trait locus qGL1 for grain length was identified with recombinant inbred lines 9311 and Nipponbare (NIP) , and fine-mapped to the OsABCB4 gene, which encodes a member of the ATP Binding Cassette B (ABCB) subfamily. Compared to NIP, loss of OsABCB4 function leads to longer and heavier grains, while over-expression of OsABCB4 causes shorter and lighter grains, demonstrating a negative control of grain length and weight in rice. Haplotype analyses using 3024 rice-sequenced genomes indicated that SNP25 and SNP55 in OsABCB4 are correlated with grain length in rice. OsbHLH166, a basic helix-loop-helix transcription factor, was screened from a yeast one-hybrid library and confirmed to directly bind the promoter of OsABCB4 by electrophoretic mobility shift assay and yeast one hybridization validation and to activate the expression of OsABCB4 by dual-luciferase reporter assay. And OsbHLH166 expressions matching OsABCB4 were all higher expressed in stems and glumes. OsABCB4 was subcellularly localized on the plasma membrane, which was verified as an auxin efflux transporter. Histological analysis, IAA content measurement, and DR5:GUS activity analyses demonstrated that OsbHLH166 and OsABCB4 control grain length by regulating cell expansion and auxin contents in glume cells and altering the expression of GL7, GS2, TGW3, and GS3 genes during rice grain development. This newly identified OsbHLH166-OsABCB4 module sheds light on our understanding of molecular mechanisms underlying the regulation of grain size and weight via auxin and provides a new gene resource for molecular design breeding of grain type.

DOI: 10.1016/j.scib.2025.04.053

Source: https://www.sciencedirect.com/science/article/abs/pii/S2095927325004578