Purple petunias reveal all

Purple petunias reveal all

A team of New Zealand researchers from AgResearch and Plant & Food Research has unlocked an elaborate code to discover how coloured pigments in plants form.

“We wanted to understand how plants control the amount of pigment they make, and when and where they produce it,” says the lead author, AgResearch scientist Dr Nick Albert.

Their paper “A conserved network of transcriptional activators and repressors regulates anthocyanin pigmentation in eudicots” has just been published in the world’s top-ranked plant biology journal, The Plant Cell.

“We were trying to understand how plants are able to control how much pigment they produce and how colour patterns form. If you like, we’ve discovered both the accelerator for turning pigment on, and the brake for slowing it down,” says the senior researcher, Plant & Food Research scientist Dr Kathy Schwinn.

President of the New Zealand Society of Plant Biologists Professor Brian Jordan says the discovery is extremely significant. “Gene regulation is critical to the control of cellular activity. This research provides profound insight into our understanding of this regulation.”

Dr Albert says they embarked on the work for two reasons.

“It’s really interesting understanding how nature works and how such elaborate colour patterns are formed in nature. They provide important insights into the way genes behave and how the way they are expressed can generate diversity in life forms.

“Pigments are hugely important for consumers – we look for them in the flowers and plants that we buy, grow and eat. Pigments and related compounds also have well documented health benefits.”

The research built on work Dr Albert had done earlier at Plant & Food Research in Palmerston North during his PhD at Massey University, where he had identified genes that controlled some of the colours in petunias.

“A lot of people have worked in this field before, but the real strength is we have joined a lot of dots together about how these genes behave. It’s quite elaborate – one gene turns on another and it turns on another,” says Dr Schwinn.

“In our experiments we altered the expression of existing genes in petunias. By removing this repressor – or the brake - the normal colour that the petunia made was enhanced. Stems and leaves that were normally green became purple - really intensely pigmented.

“If we turned the repressor on to high levels, it could turn a solid purple flower quite pale.

Depending on which of the regulatory genes you were repressing, you could get quite different colours.”

Insights from this study are already assisting scientists at Plant & Food Research to help develop fruit and vegetable cultivars with improved levels of anthocyanin pigments through conventional breeding.

“At AgResearch, we can now identify new target genes for forage crops that could increase pigmentation or tannin production,” says Dr Albert.

Plants normally contain tannins to prevent insects feeding on them. Tannin production in forages is important in agriculture because they improve nitrogen-use efficiency in the rumen, may improve animal health and productivity and can help prevent bloat.

“If we can reliably deliver tannins into the diet of sheep, cattle and deer, that’s of benefit to New Zealand farmers.”

Dr Albert’s current work at AgResearch is now looking at how tannins are regulated in clovers. “They are normally produced in the flowers and seeds but we have one species that produces a lot of tannin through the leaves, so I am looking at why it produces so much and whether there’s a way for us to use this.”

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