Identification and Characterization of Chalcone Synthase Gene Family Members in Nicotiana tabacum

Chalcone synthase (CHS, EC 2.3.1.74) is a member of the plant polyketide synthase superfamily; it catalyzes the first committed step in the flavonoid biosynthetic pathway. In this study, we identified and characterized five CHS superfamily genes from Nicotiana tabacum. Our phylogenetic analysis suggested that the five tobacco CHS genes have diverged into two subgroups, including the classical CHS genes for NtCHS1-4 and CHS-Like genes for NtCHS5. Solanaceae CHSs diverged into different subfamilies prior to the divergence of the genera. We used RNA-seq data to explore the spatial and temporal expression patterns of the NtCHS1-5 genes. NtCHS1-4 were widely expressed in pigmented or/and non-pigmented vegetative tissues and floral organs. NtCHS5 was expressed strongly in the calyx and corolla organs at the full-bloom stage. Quantitative RT-PCR analysis was performed; it verified our RNA-seq results. Further, the expression of NtCHS1 and NtCHS3 increased markedly under drought and high salt stress. NtCHS2 expression and NtCHS4 expression were obviously induced by ABA and MeJA treatment, and NtCHS4 expression was specifically induced by 2,4-D. NtCHS5 expression was not induced by any of these treatments. Our results represent new data about the differentiation of gene expression and environmental responsiveness in the expression of CHS superfamily genes in Nicotiana tabacum.