This study aims to investigate the function of the OsLRP1 gene (Os01g72490) in rice lateral root development by phenotypic characterization and expression analysis of the lrp1 mutant.

The lrp1 mutant was first identified through PCR amplification and sequencing. Bioinformatics methods were then employed to analyze the protein structure, conserved domains, transmembrane domains, and signal peptides of OsLRP1. Multiple sequence alignment and phylogenetic tree construction were conducted to explore the evolutionary relationship between OsLRP1 and LRP1 proteins from other species. Quantitative real-time PCR (qRT-PCR) was used to detect the expression levels of OsLRP1 in different rice tissues. Confocal laser scanning microscopy was utilized to observe the subcellular localization of the OsLRP1 protein. Finally, an auxin treatment experiment was performed to determine whether the regulation of lateral root development by OsLRP1 is mediated by auxin.

Phenotypic analysis revealed that compared with the wild-type Zhonghua 11, the lrp1 mutant exhibited a 32% reduction in lateral root primordia number and a 21% decrease in lateral root number. At the maturity stage, the panicle length and 100-grain weight of lrp1 were reduced by 12.5% and 7.4%, respectively, compared with the wild-type. Bioinformatics analysis showed that the OsLRP1 gene belongs to the SHI transcription factor family, encoding a protein of 340 amino acids. Conserved domain analysis indicated that it is a member of the DUF (Domain of Unknown Function) family. No signal peptide or transmembrane domain was detected in the OsLRP1 protein. Subcellular localization in tobacco demonstrated that the OsLRP1 protein is localized in the nucleus. qRT-PCR results indicated that OsLRP1 is expressed in roots, stems, and leaves, with the highest expression level in leaves. Two auxin response elements (AuxREs) were identified within the 1-kb promoter region upstream of OsLRP1. The auxin treatment experiment confirmed that lateral root development in the lrp1 mutant is affected by auxin.

In summary, OsLRP1 regulates lateral root development in rice in an auxin signaling dependent manner and is involved in rice growth, development, and stress responses, further elucidating its crucial role in rice lateral root development.