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Open Access Highly Accessed Research article

Expression of flavonoid 3’-hydroxylase is controlled by P1, the regulator of 3-deoxyflavonoid biosynthesis in maize

Mandeep Sharma1, Chenglin Chai2, Kengo Morohashi2, Erich Grotewold2, Maurice E Snook3 and Surinder Chopra1*

Author Affiliations

1 Department of Plant Science, Pennsylvania State University, University Park, Pennsylvania, PA 16802, USA

2 Center for Applied Plant Sciences and Department of Molecular Genetics, Ohio State University, Columbus, OH, 43210, USA

3 USDA-ARS, Russell Research Center, 950 College Station Road, Athens, GA, 30605, USA

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BMC Plant Biology 2012, 12:196  doi:10.1186/1471-2229-12-196

Published: 1 November 2012

Abstract

Background

The maize (Zea mays) red aleurone1 (pr1) encodes a CYP450-dependent flavonoid 3’-hydroxylase (ZmF3’H1) required for the biosynthesis of purple and red anthocyanin pigments. We previously showed that Zmf3h1 is regulated by C1 (Colorless1) and R1 (Red1) transcription factors. The current study demonstrates that, in addition to its role in anthocyanin biosynthesis, the Zmf3h1 gene also participates in the biosynthesis of 3-deoxyflavonoids and phlobaphenes that accumulate in maize pericarps, cob glumes, and silks. Biosynthesis of 3-deoxyflavonoids is regulated by P1 (Pericarp color1) and is independent from the action of C1 and R1 transcription factors.

Results

In maize, apiforol and luteoforol are the precursors of condensed phlobaphenes. Maize lines with functional alleles of pr1 and p1 (Pr1;P1) accumulate luteoforol, while null pr1 lines with a functional or non-functional p1 allele (pr1;P1 or pr1;p1) accumulate apiforol. Apiforol lacks a hydroxyl group at the 3’-position of the flavylium B-ring, while luteoforol has this hydroxyl group. Our biochemical analysis of accumulated compounds in different pr1 genotypes showed that the pr1 encoded ZmF3’H1 has a role in the conversion of mono-hydroxylated to bi-hydroxylated compounds in the B-ring. Steady state RNA analyses demonstrated that Zmf3h1 mRNA accumulation requires a functional p1 allele. Using a combination of EMSA and ChIP experiments, we established that the Zmf3h1 gene is a direct target of P1. Highlighting the significance of the Zmf3h1 gene for resistance against biotic stress, we also show here that the p1 controlled 3-deoxyanthocyanidin and C-glycosyl flavone (maysin) defence compounds accumulate at significantly higher levels in Pr1 silks as compared to pr1 silks. By virtue of increased maysin synthesis in Pr1 plants, corn ear worm larvae fed on Pr1; P1 silks showed slower growth as compared to pr1; P1 silks.

Conclusions

Our results show that the Zmf3h1 gene participates in the biosynthesis of phlobaphenes and agronomically important 3-deoxyflavonoid compounds under the regulatory control of P1.

Keywords:
Anthocyanins; Flavones; Flavonoids; F3’H; Maysin; Phlobaphenes