The TCP transcription factor TAC8 positively regulates the tiller angle in rice (Oryza sativa L.)

The tiller angle, one of the critical factors that determine the rice plant type, is closely related to rice yield. An appropriate rice tiller angle can improve rice photosynthetic efficiency and increase yields. In this study, we identified a transcription factor, TILLRE ANGLE CONTROL 8 (TAC8), that is highly expressed in the rice tiller base and positively regulates the tiller angle by regulating cell length and endogenous auxin content; TAC8 encodes a TEOSINTE BRANCHED1/CYCLOIDEA/PCF transcriptional activator that is highly expressed in the nucleus. RNA-seq revealed that TAC8 is involved mainly in the photoperiod and abiotic stress response in rice. Yeast two-hybrid assays verified that TAC8 interacts with CHLOROPHYLL A/B-BINDING PROTEIN 1, which responds to photoperiod, and haplotype analysis revealed that a 34-bp deletion at position 1516 in the promoter region and a 9-bp deletion at position 153 in the coding region can result in impaired function or loss of function of TAC8. This study provides a new genetic resource for designing ideal plant types with appropriate rice tiller angle.