AUTHOR=Lv Yanpeng , Zhang Xinfeng , Hu Yanjuan , Liu Shuang , Yin Yanbin , Wang Xiaoxue 

TITLE=BOS1 is a basic helix–loop–helix transcription factor involved in regulating panicle development in rice

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1162828

DOI=10.3389/fpls.2023.1162828

ISSN=1664-462X

ABSTRACT=<p>Panicle development is crucial to increase the grain yield of rice (<italic>Oryza sativa</italic>). The molecular mechanisms of the control of panicle development in rice remain unclear. In this study, we identified a mutant with abnormal panicles, termed <italic>branch one seed 1-1</italic> (<italic>bos1-1</italic>). The <italic>bos1-1</italic> mutant showed pleiotropic defects in panicle development, such as the abortion of lateral spikelets and the decreased number of primary panicle branches and secondary panicle branches. A combined map-based cloning and MutMap approach was used to clone <italic>BOS1</italic> gene. The <italic>bos1-1</italic> mutation was located in chromosome 1. A T-to-A mutation in <italic>BOS1</italic> was identified, which changed the codon from TAC to AAC, resulting in the amino acid change from tyrosine to asparagine. <italic>BOS1</italic> gene encoded a grass-specific basic helix–loop–helix transcription factor, which is a novel allele of the previously cloned <italic>LAX PANICLE 1</italic> (<italic>LAX1</italic>) gene. Spatial and temporal expression profile analyses showed that <italic>BOS1</italic> was expressed in young panicles and was induced by phytohormones. BOS1 protein was mainly localized in the nucleus. The expression of panicle development-related genes, such as <italic>OsPIN2</italic>, <italic>OsPIN3</italic>, <italic>APO1</italic>, and <italic>FZP</italic>, was changed by <italic>bos1-1</italic> mutation, suggesting that the genes may be the direct or indirect targets of BOS1 to regulate panicle development. The analysis of <italic>BOS1</italic> genomic variation, haplotype, and haplotype network showed that <italic>BOS1</italic> gene had several genomic variations and haplotypes. These results laid the foundation for us to further dissect the functions of BOS1.</p>