The R2R3-MYB transcription factor MiMYB1 regulates light dependent red coloration of ‘Irwin’ mango fruit skin

Abstract

The skin color of mature mango (Mangifera indica L.) fruit varies from green to red depending on cultivars. Red coloration of mango fruit skin is due to anthocyanin accumulation and is known to be induced by light exposure as in some other fruit crops. Recently, several investigations on the genes involved in anthocyanin biosynthesis in mango fruit skin have been conducted, to understand the molecular mechanism underlying red coloration of the mango fruit. In the present study, we investigated the characteristics of four R2R3-MYB transcription factors (TF) including MiMYB1, which is assumed to be the MYB TF regulating anthocyanin biosynthesis in mangoes. The deduced amino acid sequence of MiMYB1 showed a high degree of similarity with the anthocyanin-related R2R3-MYB TFs from other plant species and contained two conserved motifs defining the anthocyanin-related MYB TFs. Expression analysis in the mango fruit skin under different light conditions showed that the expression of MiMYB1 increased as the intensity of light exposure increased, parallel to anthocyanin accumulation and the expression of some structural genes of the anthocyanin biosynthetic pathway. In addition, a transient expression assay of tobacco leaves showed that co-infiltration of MiMYB1 and MibHLH2, which is a bHLH TF of mango, induced anthocyanin accumulation in tobacco leaves. These results suggest that MiMYB1 acts as the key regulator for anthocyanin biosynthesis in mango fruit skin, and that light-dependent red coloration of mango fruit skin is regulated by MiMYB1 in transcript levels.