LTD1 plays a key role in rice tillering regulation through cooperation with CycH1;1 and TFB2 subunits of the TFIIH complex

Xiaorong Yang, Chun Hu, Xiangyu Zhang, Xiaolan Wang, Longfei Chen, Hongshan Zhang, Xinxin Ma, Ke Liang, Congping Chen, Jia Guo, Chun Li, Bin Yang, Changhui Sun, Xiaojian Deng* and Pingrong Wang*

The Plant Journal (2025) 122, e70119, 31 March 2025 (IF=6.392)

https://doi.org/10.1111/tpj.70119

SUMMARY

Tillering contributes greatly to grain yield in rice (Oryza sativa). At present, many genes involved in rice tillering regulation have been cloned and characterized. However, identification of more novel genes is still necessary to full understand the molecular mechanisms regulating rice tillering. In this study, we isolated a low-tillering and dwarf 1 (ltd1) mutant in indica rice. Map-based cloning and MutMap analysis showed that candidate gene LTD1 (LOC_Os01g19760) encodes a putative FAM91A1 protein with unknown function in plants. LTD1-complementation and -RNAi confirmed that LTD1 is responsible for the mutant phenotype of ltd1. The LTD1 protein is localized to the plasma membrane, endoplasmic reticulum and multi-vesicular bodies. Furthermore, protein interaction and colocalization assays showed that LTD1 interacts with both TFB2 subunit of the core subcomplex and CycH1;1 subunit of the cyclin-dependent kinase–activating kinase (CAK) subcomplex of  TFIIH complex, and TFB2 also interacts with CycH1;1. qRT-PCR demonstrated that expression levels of most genes related to cell cycle are changed significantly in the ltd1 tiller buds, and flow cytometry assay revealed that there are more polyploid nuclei in the ltd1 leaves, suggesting that LTD1 could be involved in cell cycle regulation. Taken together, our findings indicated that LTD1 plays a key role in rice tillering regulation by involvement in cell cycle through cooperation with CycH1;1 and TFB2 subunits of TFIIH. This work also sheds light on the biological function of FAM91A1 in regulating important agronomic traits of rice.

Keywords: rice (Oryza sativa), tillering, yield potential, FAM91A1 protein, TFIIH complex, cell cycle.