Cloning and functional analysis of the dwarf and multi-tiller gene <italic>DMT1</italic> in rice

Tiller number is a key determinant of rice yield. In this study, we identified a novel natural dwarf and high-tillering mutant, dmt1 (dwarf and multi-tiller 1), which exhibited a tiller number of 155.07±18.53—12.64 times that of the wild type HY67. However, several agronomic traits, including plant height, panicle length, seed setting rate, grain length, and 1000-grain weight, were significantly reduced in dmt1 compared to HY67. Histological analysis suggested that the increased tiller number in dmt1 may result from the premature elongation of tiller buds. Genetic analysis indicated that the dwarf and high-tillering phenotype of dmt1 is controlled by a single recessive locus. Using positional cloning and gene silencing, we successfully isolated the DMT1 gene. Sequence analysis revealed that DMT1 is a novel allele harboring a point mutation in D10/OsCCD8 (LOC_Os01g54270), a key gene in the strigolactone (SL) biosynthesis pathway. The DMT1 protein consists of only the first 279 amino acids of the N-terminal region of OsCCD8. RT-qPCR analysis showed significant differences in the expression levels of genes related to the SL and indole-3-acetic acid (IAA) pathways between HY67 and dmt1. Moreover, exogenous application of IAA significantly induced OsCCD8/DMT1 expression and increased the levels of the SL intermediate products carlactone (CL) and 5-deoxystrigol (5-DS), suggesting that OsCCD8/DMT1 may serve as a key regulatory node in the crosstalk between IAA and SL signaling. This study enriches our understanding of OsCCD8 function and provides valuable genetic material for dissecting the functional domains of the OsCCD8 protein, with important implications for high-yield rice breeding.