A Systems Biology Approach Identifies a R2R3 MYB Gene Subfamily with Distinct and Overlapping Functions in Regulation of Aliphatic Glucosinolates

Ida Elken Sønderby,Carla Ticconi,Nanna Bjarnholt,Bjarne Gram Hansen,Daniel J Kliebenstein,Barbara Ann Halkier,Ivan Baxter

doi:10.1371/journal.pone.0001322

Ida Elken Sønderby, Carla Ticconi + Show 5 more

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https://doi.org/10.1371/journal.pone.0001322

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Journal: PloS one	Publication Date: Dec 19, 2007
Citations: 364	License type: CC BY 4.0

Affiliation: University of Copenhagen, University of California, Davis

Abstract

BackgroundGlucosinolates are natural metabolites in the order Brassicales that defend plants against both herbivores and pathogens and can attract specialized insects. Knowledge about the genes controlling glucosinolate regulation is limited. Here, we identify three R2R3 MYB transcription factors regulating aliphatic glucosinolate biosynthesis in Arabidopsis by combining several systems biology tools.Methodology/Principal Findings MYB28 was identified as a candidate regulator of aliphatic glucosinolates based on its co-localization within a genomic region controlling variation both in aliphatic glucosinolate content (metabolite QTL) and in transcript level for genes involved in the biosynthesis of aliphatic glucosinolates (expression QTL), as well as its co-expression with genes in aliphatic glucosinolate biosynthesis. A phylogenetic analysis with the R2R3 motif of MYB28 showed that it and two homologues, MYB29 and MYB76, were members of an Arabidopsis-specific clade that included three characterized regulators of indole glucosinolates. Over-expression of the individual MYB genes showed that they all had the capacity to increase the production of aliphatic glucosinolates in leaves and seeds and induce gene expression of aliphatic biosynthetic genes within leaves. Analysis of leaves and seeds of single knockout mutants showed that mutants of MYB29 and MYB76 have reductions in only short-chained aliphatic glucosinolates whereas a mutant in MYB28 has reductions in both short- and long-chained aliphatic glucosinolates. Furthermore, analysis of a double knockout in MYB28 and MYB29 identified an emergent property of the system since the absence of aliphatic glucosinolates in these plants could not be predicted by the chemotype of the single knockouts.Conclusions/SignificanceIt seems that these cruciferous-specific MYB regulatory genes have evolved both overlapping and specific regulatory capacities. This provides a unique system within which to study the evolution of MYB regulatory factors and their downstream targets.

Highlights

Glucosinolates are amino acid-derived natural plant products characteristic of the order Brassicales, including the agriculturally important oilseed rape, the Brassica vegetables and the model plant Arabidopsis [1,2]
The analysis revealed that myb28-1, myb29-1 and myb29-2 were knockout mutants whereas myb76-1 and myb76-2 still had residual but much reduced MYB76 transcript levels (Figure 7B)
The myb28-1 mutant showed a dramatic reduction in long-chained and a decrease in short-chained aliphatic glucosinolates (Table 4). These results indicate that MYB29 and MYB76 play a role for regulation of short-chained aliphatic glucosinolates, whereas MYB28 plays a role in the control of both short- and longchained aliphatic glucosinolates in leaves

Summary

Introduction

Glucosinolates are amino acid-derived natural plant products characteristic of the order Brassicales, including the agriculturally important oilseed rape, the Brassica vegetables and the model plant Arabidopsis [1,2]. The completion of the Arabidopsis genomic sequence has resulted in identification of most of the biosynthetic genes involved in the formation of the core structure, the chain-elongation machinery and secondary modifications (Figure 1). Glucosinolates are natural metabolites in the order Brassicales that defend plants against both herbivores and pathogens and can attract specialized insects. We identify three R2R3 MYB transcription factors regulating aliphatic glucosinolate biosynthesis in Arabidopsis by combining several systems biology tools. A phylogenetic analysis with the R2R3 motif of MYB28 showed that it and two homologues, MYB29 and MYB76, were members of an Arabidopsis-specific clade that included three characterized regulators of indole glucosinolates. It seems that these cruciferousspecific MYB regulatory genes have evolved both overlapping and specific regulatory capacities. This provides a unique system within which to study the evolution of MYB regulatory factors and their downstream targets

Methods

Results

Conclusion