Abstract

Background Multiple MYB transcription factors (TFs) are involved in the regulation of plant coloring. Betalain is a kind of natural plant pigment and its biosynthesis is regulated by a number of enzymes. Despite this, little is known about the molecular properties and roles of MYB TFs in pitaya betalain biosynthesis. Results In the present study, we identified a 1R-MYB gene, HuMYB132 , which is preferentially expressed in red-pulp pitaya at the mature stage. It was clustered with Arabidopsis R-R-type genes and had two DNA-binding domains and a histidine-rich region. The expression assays in N . benthamiana and yeast indicated that HuMYB132 is a nucleus-localized protein with transcriptional activation activity. Dual luciferase reporter assay and electrophoretic mobility shift assays (EMSA) demonstrated that HuMYB132 could promote the transcriptional activities of HuADH1 , HuCYP76AD1–1 , and HuDODA1 by binding to their promoters. Silencing HuMYB132 reduced betalain accumulation and the expression levels of betalain biosynthetic genes in pitaya pulps. Conclusions According to our findings, HuMYB132 , a R-R type member of 1R-MYB TF subfamily, positively regulates pitaya betalain biosynthesis by regulating the expression of HuADH1 , HuCYP76AD1–1 , and HuDODA1 . The present stud y provides a new theoretical reference for the management of pitaya betalain biosynthesis and also provides an essential basis for future regulation of betalain biosynthesis in Hylocereus.