Divergent evolution of the chalcone synthase gene family in Phalaenopsis orchids

The evolutionary success of orchid family is driven by its extraordinary adaptation. Chalcone synthase (CHS) gene encodes the key enzyme for biosynthesis of flavonoids, secondary metabolites important for plant adaptation. Kuo et al. report the first chromosome-scale study of CHS genes in Phalaenopsis orchids.

Five paralogous CHS genes identified from Ph. aphrodite transcriptomic datasets were classified into three groups that were localised on three distinct chromosomes by high-resolution FISH mapping. Their sequence divergences and expression profiles are highly correlated with their chromosomal distributions. Kuo et al. propose that the expansion of the CHS gene family occurred through segmental duplications, followed by tandem duplications.