The bHLH transcription factor PIL1 orchestrates starch synthesis in key cereal crops
Yanjun Meng, Jiaxing Cui, Wenbo Zeng, Xinji Li, Changqing Du, Pengfei Wang, Gezi Li, Q. X. Ge, Tiancai Guo, Guozhang Kang
Abstract
Key cereal crops, including wheat, rice and maize, supply nearly 50% of the world’s caloric intake, with starch constituting over 70% of the grain weight. However, the regulatory mechanisms underlying starch synthesis are poorly understood. In this study, we identify a transcription factor TaPIL1-5D, which binds to the promoters of ADP-glucose pyrophosphorylase small subunit 1 (TaAGPS1a−7A), granule-bound starch synthase I (TaGBSSI−4A), and branching enzyme II b (TaBEIIb-2D). Similarly, its homologous OsPIL11 and ZmPIL1 also activate the expression of the AGPS1, BEIIb, and GBSSI, and positively regulates grain starch synthesis. TaPIL1-5D and ZmPIL1 improve grain yields in two successive years. Nine alleles of TaPIL1-5B form three distinct haplotypes (Hap1-3), while TaPIL1-5B-Hap1 is repressed due to its binding by the transcriptional repressor TaBZR1.1. Additionally, TaPIL1-5B interacts with TaPIL1-5D in the nucleus, enhancing its transcriptional activation. Collectively, our study enriches the starch regulatory network and provides a promising tool for improving starch content. Starch is a major component of wheat grains. Here the authors show that the PIL1 transcription factor positively regulates grain starch synthesis and identify elite alleles that could be used to enhance wheat yield and starch content.