TH1, a DUF640 domain-like gene controls lemma and palea development in rice

The developmental regulation of grasses lemma and palea and their relationship to the floral organs in dicots had been variously explicated and extensively debated. Here, we characterized a triangular hull mutant th1-1 from EMS-mutagenized Oryza sativa ssp. indica cv. 93-11. The th1-1 mutant exhibited obviously triangular hull with tortuous and slender lemma/palea. Using a map-based cloning strategy, the TH1 gene was narrowed down to a 60-kb region on the long arm of chromosome 2. Sequence verification revealed that the th1-1 mutant harbored 1-bp deletion in exon 2 of LOC_Os02g56610 which resulted in a frame-shift mutation. The RNA-interference transgenic plants of LOC_Os02g56610 displayed a similar phenotype to the th1 mutant. Consequently, LOC_Os02g56610 was identified as the TH1 gene which encoded 248 amino acids and contained a DUF640 domain. RT-PCR analysis and GUS staining showed that the transcripts of TH1 mainly accumulated in young inflorescence, lemma and palea of spikelet. These results suggested that TH1 was an important gene controlling the lemma and palea development in rice.