5-Azacytidine downregulates the SABATH methyltransferase genes and augments bixin content in Bixa orellana L. leaves

Abstract

Bixa orellana L. seeds are an important source of the liposoluble apocarotenoid bixin and the natural hydrosoluble dye norbixin. These natural dyes are used for food, pharmaceutical, and cosmetic applications. The participation of methyltransferases has already been demonstrated in the bixin biosynthesis pathway, and the alteration of these genes expression can lead to changes in the production of bixin. Treatment with demethylating agents, such as 5-azacytidine (5-AzaC), was previously related to an increased production of secondary compounds and serves for the study of secondary metabolism pathways in plants. Here, we evaluated for the first time the effect of 5-AzaC on the expression of SABATH methyltransferase genes as well as some bixin pathway candidate genes, global DNA methylation, and bixin, chlorophylls, and total carotenoid content in the leaves of B. orellana plants cultured in vitro. Exposing shoot apexes to 5-AzaC for 48 h affected global genome methylation but did not alter chlorophylls and total carotenoid content in the leaves of B. orellana. Importantly, plants submitted to this demethylating agent exhibited downregulation of the SABATH and CCD4 families of genes, upregulation of the ALDH3H1 gene, and increased bixin content in the leaves, suggesting that this methyltransferase inhibitor can selectively regulate the biosynthesis and production of bixin in B. orellana by an unknown mechanism. Moreover, here we demonstrate the possibility to use 5-AzaC to increase bixin contents in B. orellana plants. The methyltransferase inhibitor, 5-Azacytidine, can selectively regulate the biosynthesis and production of bixin in annatto plant leaves, by upregulating BoALDH3H1 gene and downregulating BoSABATH and BoCCD4 gene families.