Class I TCP transcription factor OsTCP4 suppresses plant height via negatively regulating the green revolution gene SD1 (OsGA20ox2) in rice (Oryza sativa).

Abstract

Plant height is critical for crops in agricultural research and practice. Optimizing plant height helps to increase yield and lodging resistance. The green revolution gene semi-dwarf 1 (SD1) encoding GA 20-oxidase 2 (GA20ox2) has been widely used in modern rice breeding. However, the molecular mechanism of how SD1 is transcriptionally regulated remains elusive. TCP proteins, one family of the plant-specific transcription factors (TFs), have been proved to widely distribute in plants and play important roles in plant growth and development. Here, we report a TCP TF OsTCP4, which belongs to class I clade TCP, plays critical roles in regulating plant height of rice through acting as a transcriptional repressor of SD1. OsTCP4 is a nuclear-localized TF, which has a preferential transcriptional accumulation in stem nodes and tiller bases. ostcp4 knock-out mutants displayed higher plant height compared with WT, while overexpression of OsTCP4 reduced plant height compared with WT, which was confirmed by two cultivars on four planting sites of Yunnan under three-year investigation. The expression of SD1 was upregulated in ostcp4 mutants and reduced in OsTCP4-overexpression plants. Moreover, OsTCP4 protein directly binds to the promoter region of SD1. The genetic regulation between OsTCP4 and SD1 was further verified with ossd1 tcp4 double mutant. Moreover, distinction of plant height in ostcp4 lines and OsTCP4-OE lines is caused by different concentrations of GA₁. Taken together, OsTCP4 acts as a transcriptional repressor of SD1 and it may play a critical role in rice growth and development through the fine-tuning of GA₁ biosynthesis.