AmPIF4 negatively regulates the blue light-induced synthesis of volatile terpenoids in snapdragon

Abstract Background Floral secondary metabolites, especially terpenoids, play a key role in plant defense and reproduction. Terpenoids are the most abundant floral volatiles, and their synthesis and release are affected by light quality. Blue light can significantly enhance the emissions of terpenoids as well as the expression of biosynthesis-related genes in snapdragon. However, the regulatory mechanism of blue light-induced terpenoid biosynthesis remains unclear. Results In this study, the transcription factor (TF) PHYTOCHROME-INTERACTING FACTOR 4 (AmPIF4) was identified and found to be lowly expressed under blue light, which was in contrast to the expression of ocimene synthase (AmOCS) and myrcene synthase (AmMYS), 1-deoxy-D-xylulose 5-phosphate (DXP) synthase (AmDXS), and DXP reductoisomerase (AmDXR). AmOCS and AmMYS expression and the relative emissions of ocimene and myrcene were up-regulated in response to AmPIF4 silencing. Moreover, AmPIF4 negatively regulated terpenoid biosynthesis by binding to the promoters of biosynthesis-related genes. The transcriptional activation activity of AmPIF4 was increased in AmCRY1-silenced flowers. In addition, AmPIF4 interacted with AmCRYs (Cryptochromes) and AmCOP1 (CONSTITUTIVELY PHOTOMORPHOGENIC 1), which are key blue light signal receptors. Conclusion Overall, our results reveal a novel molecular mechanism involving AmPIF4 that contributes to the blue light-mediated regulation of terpenoid biosynthesis in snapdragon.