Dw1, an Important Gene for Lodging Resistance and Mechanical Harvesting of Sorghum, Encodes a Novel Protein Involved in Cell Proliferation

Dwarfing (or semi-dwarfing) genes have contributed to enhanced lodging resistance and efficiency of mechanical harvesting, resulting in increased crop productivity. A spontaneous mutation, dw1 was found in 1905, and it has been widely used as an important dwarfing gene in the history of grain sorghum breeding all over the word. Here, we report the identification and characterization of Dw1. We carried out QTL cloning, and revealed that Dw1 encodes a novel uncharacterized protein. T-DNA insertion or knockdown lines of orthologous genes in Arabidopsis and rice also showed semi-dwarfism similar to that of a nearly isogenic line carrying dw1 (NIL-dw1) of sorghum. A histological analysis of NIL-dw1 and wildtype (WT) revealed that the longitudinal parenchymal cell lengths of the internode were almost the same between NIL-dw1 and WT, while the number of cells per internode was significantly reduced in NIL-dw1 compared with WT. Additionally, NIL-dw1dw3, carrying both dw1 and dw3 (reduced activity of auxin transport), showed a synergistic phenotype for the cell number. These observations suggest that the DW1 increased the cell proliferation activity in the internodes in WT, and the combination of dw1 and dw3 produces the synergistic effect, which have been contributed to improve lodging resistance and mechanical harvesting.