NbCycB2 represses Nbwo activity via a negative feedback loop in the tobacco trichome development

The wo protein and its downstream gene, SlCycB2 have been demonstrated to regulate the trichome development in tomato. It was shown that only gain-of-function mutant form of wo, WoV (wo woolly motif mutant allele) could induce the increase of trichome density. However, it is still unclear the relationships between wo, WoV and SlCycB2 in trichome regulation. In this study, we demonstrated Nbwo (NbWoV) directly regulated the expressions NbCycB2 by binding to the promoter of NbCycB2 and its genomic sequences. As a feedback regulation, NbCycB2 negatively regulates the trichome formation by repressing Nbwo activity at protein level. We further found that the mutations of Nbwo woolly motif could prevent repression of NbWoV by NbCycB2, which results in the significant increase of active Nbwo proteins, trichome density and branches. Our results revealed a novel reciprocal mechanism between NbCycB2 and Nbwo during the trichome formation in Nicotiana benthamiana.