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

The transcription factor Woolly (Wo) and its downstream gene CycB2 have been shown to regulate trichome development in tomato (Solanum lycopersicum). It has been demonstrated that only the gain-of-function allele of Slwo (SlWoV, the Slwo woolly motif mutant allele) can increase the trichome density; however, it remains unclear why the two alleles function differently in trichome development. In this study, we used Nicotiana benthamiana as a model and cloned the homologues of Slwo and SlCycB2 (named Nbwo and NbCycB2). We also constructed a Nbwo gain-of-function allele with the same mutation site as SlWoV (named NbWoV). We found that both Nbwo and NbWoV directly regulate NbCycB2 and their own expression by binding to the promoter of NbCycB2 and their own genomic sequences. As form of a feedback regulation, NbCycB2 negatively regulates trichome formation by repressing Nbwo activity at the protein level. We also found that mutations in the Nbwo woolly motif can prevent repression of NbWoV by NbCycB2, which results in a significant increase in the amount of active Nbwo proteins and in increases in trichome density and the number of branches. Our results reveal a novel reciprocal regulation mechanism between NbCycB2 and Nbwo during trichome formation in N. benthamiana.

The complete mitochondrial genome sequence of Drepanidotaenia lanceolata (Cyclophyllidea: Hymenolepididae).

The complete mitochondrial genome of Drepanidotaenia lanceolata was sequenced. The complete mtDNA sequence is 13 573 bp long and contains 12 protein-coding genes (cox1-3, nad1-6, nad4L, atp6, and cytb), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and 2 non-coding regions (NCR). Phylogenetic analysis using three methods (Bayesian inference, maximum parsimony, and maximum likelihood) demonstrates with high statistical support that D. lanceolata is closely related to the genus Hymenolepis. This study reports the first complete mt genome sequence of a representative species of the genus Drepanidotaenia and should provide novel genetic data for further studies of the taxonomy, systematics, and population genetics of these and other related cestodes of socio-economic significance.