The tomato B-type cyclin gene, SlCycB2, plays key roles in reproductive organ development, trichome initiation, terpenoids biosynthesis and Prodenia litura defense

- SlCycB2-OE led to abnormal flower with the unclosed stamen, shortened style and aberrant pollen.
- Nearly all non-glandular trichomes (including type III and V), as well as the glandular ones of type I and type VI were disappeared in SlCycB2-OE lines. On the contrary, suppression of SlCycB2 could promote type III and type V trichomes formation.
- The production of monoterpene and sesquiterpene were significantly decreased in SlCycB2-OE plants, which thus caused the reduction of the defense against Prodenia litura.
- Transcriptome profile demonstrated that the differentially expressed genes mainly participate in the biosynthesis of terpenes, cutin, suberine and wax.
- Several homologs of SlCycB2 gene in many plants, such as SlCycB3 in tomato, NtCycB2 in tobacco, AtCycB2 in Arabidopsis, have similar regulatory functions in trichome formation.

Cyclins exist extensively in various plant species. Among them, B-type cyclins play important roles in the transition of G2-to-M. However, few B-type cyclins have been reported to participate in reproductive organ development and trichome formation. In this study, transgene analysis showed that SlCycB2 overexpression caused abnormal flower with the unclosed stamen, shortened style and aberrant pollen. In addition, nearly all non-glandular trichomes, as well as the glandular ones were disappeared. On the contrary, suppression of SlCycB2 could promote type III and type V trichomes formation. Detection of secondary metabolites indicated that the production of monoterpene and sesquiterpene were significantly decreased in SlCycB2-OE plants, which thus resulted in the reduction of the defense against Prodenia litura. Transcriptome profile demonstrated that the differentially expressed genes mainly participate in the biosynthesis of terpenes, cutin, suberine and wax. Furthermore, we identified several homologs of SlCycB2, SlCycB3, NtCycB2, AtCycB2, which have similar regulatory functions in trichome formation. These results indicate that SlCycB2 plays a critical role in reproductive organ development, multicellular trichome initiation, secondary metabolite biosynthesis and Prodenia litura defense in tomato. The similar roles of its homologs in multicellular trichome formation suggest that Solanaceous species may share common regulatory pathway.