TaCOLD1 defines a new regulator of plant height in bread wheat.

Plant height is among the most important agronomic traits that influence crop yield. However, in addition to the Rht-1 alleles, the molecular basis of plant height in bread wheat remains largely unclear. Based on wheat gene expression profiling analysis, we identify a light-regulated gene from bread wheat, designated as TaCOLD1, whose encoding protein is homologous to cold sensor COLD1 in rice. We show that TaCOLD1 protein is localized to the endoplasmic reticulum (ER) and plasma membrane. Phenotypic analyses show that overexpression of a mutated form of TaCOLD1 (M187K) in bread wheat cultivar Kenong199 (Rht-B1b) background resulted in an obvious reduction in plant height. Further, we demonstrate that the hydrophilic loop of TaCOLD1 (residues 178-296) can interact with TaG alpha-7A (the alpha subunit of heterotrimeric G protein) protein but not TaG alpha-1B, and the mutation (M187K) in TaCOLD1 remarkably enhances its interaction with TaG alpha-7A. Physical interaction analyses show that the C-terminal region of TaG alpha-7A, which is lacking in the TaG alpha-1B protein, is necessary for its interaction with TaCOLD1. Intriguingly, the C-terminal region of TaG alpha-7A is also physically associated with the TaDEP1 protein (an atypical G gamma subunit). Significantly, we discover that TaCOLD1 and mTaCOLD1 (M187K) can interfere with the physical association between TaG alpha-7A and TaDEP1. Together, this study reveals that TaCOLD1 acts as a novel regulator of plant height through interfering with the formation of heterotrimeric G protein complex in bread wheat and is a valuable target for the engineering of wheat plant architecture.