Repression of GhTUBB1 Reduces Plant Height in Gossypium hirsutum

The original 'Green Revolution' genes are associated with gibberellin deficiency. However, in some species, mutations in these genes cause pleiotropic phenotypes, preventing their application in dwarf breeding. The development of novel genotypes with reduced plant height will resolve this problem. In a previous study, we obtained two dwarf lines, L28 and L30, by introducing the Ammopiptanthus mongolicus (Maxim. ex Kom.) Cheng f. C-repeat-binding factor 1 (AmCBF1) into the upland cotton variety R15. We found that Gossypium hirsutum Tubulin beta-1 (GhTUBB1) was downregulated in L28 and L30, which suggested that this gene may have contributed to the dwarf phenotype of L28 and L30. Here, we tested this hypothesis by silencing GhTUBB1 expression in R15 and found that decreased expression resulted in a dwarf phenotype. Interestingly, we found that repressing AmCBF1 expression in L28 and L30 partly recovered the expression of GhTUBB1. Thus, AmCBF1 expression presented a negative relationship with GhTUBB1 expression in L28 and L30. Moreover, yeast one-hybrid and dual-luciferase assays suggest that AmCBF1 negatively regulates GhTUBB1 expression by directly binding to C-repeat/dehydration-responsive (CRT/DRE) elements in the GhTUBB1 promoter, potentially explaining the dwarf phenotypes of L28 and L30. This study elucidates the regulation of GhTUBB1 expression by AmCBF1 and suggests that GhTUBB1 may be a new target gene for breeding dwarf and compact cultivars.