Epistatic Interactions Influencing Anthocyanin Gene Expression in Capsicum annuum

Anthocyanin pigmentation in leaves, flowers, and fruit imparts violet to black color and enhances both ornamental and culinary appeal. Shades of violet to black pigmentation in Capsicum annuum L. are attributed to anthocyanin accumulation. Anthocyanin production is markedly influenced by numerous environmental factors, including temperature and light stress. The objective of this study was to determine the genetic basis for differences in C. annuum anthocyanin content in response to varying environments. Growth experiments conducted under controlled environment conditions demonstrated that anthocyanin concentration was significantly higher in mature leaves in comparison with immature leaves under high light (435 μmol·s −1 ·m −2 ) conditions. High (30 °C day/25 °C night) versus low (20 °C day/15 °C night) temperature had no significant effect on anthocyanin concentration regardless of leaf maturity stage. Foliar anthocyanin concentration in plants grown under short days (10 h) with low light intensity (215 μmol·s −1 ·m −2 ) was significantly less than under long days (16 h) with low light. Under high light intensity, daylength had no effect on anthocyanin content. Three structural genes [chalcone synthase ( Chs ), dihydroflavonol reductase ( Dfr ), anthocyanin synthase ( Ans )] and three regulatory genes ( Myc , Myb A , Wd40 ) were selected for comparison under inductive and noninductive environmental conditions for anthocyanin accumulation. Expression of Chs, Dfr , and Ans was significantly higher in mature leaves in comparison with younger leaves. Consistent with anthocyanin concentration, temperature had no effect on structural gene expression, whereas light positively influenced expression. Under low light conditions, temperature had no effect on Myc , Myb A , and Wd40 expression; whereas under high light conditions, temperature only had an effect on Myb A expression. The study of anthocyanin leaf pigmentation in C. annuum under inductive and noninductive environments provides a new approach for elucidating the molecular genetic basis of epistatic gene interactions and the resulting phenotypic plasticity.