Fine Mapping of the Affecting Tillering and Plant Height Gene CHA-1 in Rice

The plant architecture of rice is an important factor affecting yield. Strigolactones (SLs) are newly discovered carotenoid-derived plant hormones that play an important role in rice plant architecture. In this study, a high-tillering dwarf mutant, CHA-1, was identified by spatial mutagenesis. CHA-1 was located in the region of 31.52-31.55 MB on chromosome 1 by map-based cloning. Compared with the wild-type THZ, the CHA-1 mutant showed that ACCAC replaced TGGT in the coding region of the candidate gene LOC_Os01g54810, leading to premature termination of expression. Genetic complementation experiments proved that LOC_Os01g54810 was CHA-1, which encodes a putative member of Class III lipase. Expression analysis showed that CHA-1 was constitutively expressed in various organs of rice. Compared with those in THZ, the expression levels of the D17 and D10 genes were significantly downregulated in the CHA-1 mutant. In addition, the concentrations of ent-2'-epi-5-deoxystrigol (epi-5DS) in the root exudates of the CHA-1 mutant was significantly reduced compared with that of THZ, and exogenous application of GR24 inhibited the tillering of the CHA-1 mutant. These results suggest that CHA-1 influences rice architecture by affecting SL biosynthesis.