Japanese scientists have identified genes controlling the production of important compounds, known as
glucosinolates, produced in food crops. Vegetable plants from the family Brassicaceae, such as cabbage,
broccoli and cauliflower, produce glucosinolates, which are useful in human health and to the
environment. They are anti-carcinogenic with antioxidant properties and offer a natural defense against
crop pests, potentially reducing the need for synthetic pesticides.
The biosynthesis of glucosinolates was poorly understood until the research team, led by Masami Yokota
Hirai and Kazuki Saito from RIKEN’s Plant Science Center in Yokohama, used an ‘omics-based approach’,
combining transcriptome and metabolome data to describe this process1. The transcriptome includes all
transcribed genes in certain conditions, and the metabolome comprises all the end products of gene
expression. Integrating these sets of information gives a more complete picture of the biosynthetic
pathway under study (Fig. 1 - Click on link below).
According to Hirai and Saito, the omics-based approach can be used to comprehensively identify a set of
genes involved in a particular metabolic pathway—it can be a powerful tool used to distinguish the most
important gene of many that may encode a particular transcription factor. A transcription factor is a
protein that controls when and where those genes are expressed.
The researchers revealed that long-chain, or aliphatic, glucosinolate biosynthesis is associated with two
uncharacterized transcription factor genes, Myb28 and Myb29, by comparing the condition-independent
transcriptome data with condition-specific information—a procedure called transcriptome coexpression
analysis. Myb28 is a master transcription factor controlling many genes and Myb29 is an accessory. In
the model plant Arabidopsis, the team then overexpressed Myb28 and found a huge increase in the
production of glucosinolates; and in a mutant lacking Myb28, they found a decrease in production. The
team later renamed these genes Production of Methionine-Derived Glucosinolate (PMG) 1 and 2.
This is the first report of genes regulating the aliphatic glucosinolate biosynthetic pathway. It shows that
transcriptome coexpression analysis is highly versatile and suitable for comprehensively identifying
genes involved in plant metabolism. A greater understanding of metabolic systems will lead to
subsequent biotechnological applications.
“We eat Brassicaceae vegetables daily,” says Hirai. “By over-expressing PMG1 or controlling the
expression of its orthologs in these vegetables, we can develop physiologically functional vegetables
with higher amount of glucosinolates.” This could be useful in human nutrition. These genes are
promising targets for the genetic engineering of glucosinolate production, possibly on an industrial scale.
Reference
1. Hirai, M.Y., Sugiyama, K., Sawada, Y., Tohge, T., Obayashi, T., Suzuki, A., Araki, R., Sakurai, N., Suzuki, H., Aoki, K. et al.
Omics-based identification of Arabidopsis Myb transcription factors regulating aliphatic glucosinolate
biosynthesis. Proceedings of the National Academy of Sciences USA 104, 6478–6483 (2007).
