DWARF AND LESS TILLERS ON CHROMOSOME 3 Promotes Tillering in Rice by Sustaining FLORAL ORGAN NUMBER 1 Expression.

Three key factors determine yield in rice (Oryza sativa): panicle number, grain number, and grain weight. Panicle number is strongly associated with tiller number. Although many genes regulating tillering have been identified, whether Dof proteins are involved in controlling plant architecture remains unknown. The dwarf and less tillers on chromosome 3 (dlt3) rice mutant produces fewer tillers than the wild type. We cloned DLT3, which encodes a Dof protein that interacts with MONOCULM 3 (MOC3) in vivo and in vitro and recruits MOC1, forming a DLT3-MOC3-MOC1 complex. DLT3 binds to the promoter of FLORAL ORGAN NUMBER 1 (FON1) to activate its transcription and positively regulate tiller number. The overexpression of MOC1, MOC3, or FON1 in the dlt3 mutant increased tiller number. Collectively, these results suggest a model in which DLT3 regulates tiller number by maintaining the expression of MOC1, MOC3, and FON1. We discovered that DLT3 underwent directional selection in the Xian/indica and Geng/japonica populations during rice domestication. To provide genetic resources for breeding varieties with optimal panicle numbers, we performed large-scale diversity sequencing of the 1080-bp DLT3 coding region of 531 accessions from different countries and regions. Haplotype analysis showed that the superior haplotype, DLT3H1, produced the most tillers, while haplotype DLT3H6 produced the fewest tillers. Our study provides important germplasm resources for breeding super high-yielding rice varieties with combinations of superior haplotypes in different target genes, which will help overcome the challenge of food and nutritional security in the future.

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