A Novel Lateral Organ Boundary-domain Factor CmLBD2 Positively Regulates Pollen Development by Activating CmACOS5 in Chrysanthemum morifolium

Male sterility, as a common reproductive characteristic in plants, plays an important role in breeding, in which pollen abortion is a key factor leading to male sterility. Here, based on a low expression level gene CmACOS5 in transcriptome of pollen abortive chrysanthemum, a new transcription factor CmLBD2 of the Lateral Organ Boundaries Domain family, which could bind the promoter of CmACOS5 by yeast one-hybrid library was screened. This study revealed the origin and expression pattern of CmLBD2 in chrysanthemum and verified the functions of two genes in pollen development by transgenic means. Inhibiting the expression of CmACOS5 or CmLBD2 can lead to a large reduction in pollen and even abortion in chrysanthemum. Using yeast one-/two-hybrid, electrophoretic mobility shift assays, and luciferase reporter assays, it was verified that CmLBD2 directly binds to the promoter of CmACOS5. These results suggest that LBD2 is a novel, key transcription factor regulating pollen development. This result will provide a new research background for enriching the function of LBD family proteins and also lay a new foundation for the breeding of male sterile lines and the mechanism of pollen development.