United Kingdom
June 2, 2016
Glossy and matte varieties of wheat
In young plants, you can sometimes distinguish cultivated wheat varieties from wild species by their colour. Wild wheat appears either glossy green or a matte bluish-grey, but cultivated varieties are almost always the latter. The bluish-grey colour comes from a waxy film thought to increase yields and protect the plant from environmental stress, particularly drought and diseases. The genes that produce the coating have long eluded researchers, but work by an international team has now revealed them. The team was led by the Weizmann Institute in Israel, and includes scientists at Rothamsted Research, which receives strategic funding from the BBSRC. The findings, reported recently in The Plant Cell, may in the future be used to impart sturdiness to crops.
The bluish-grey coating appears only at certain stages in plant growth or in certain organs, reinforcing the idea that it helps to defend the plant. Identifying the genes involved in creating the coating has been difficult, however, as the wheat genome contains multiple sets of chromosomes and repeated copies of some of the genes. The scientists looked at the genomes of two different types of wheat: glossy-green and bluish-grey. They compared gene activity in these two wheat types using various methods, including next-generation RNA sequencing technology, which can simultaneously measure the expression of vast numbers of genes. The team also made use of the full readout of the wheat genome, sequenced recently.
The team found a cluster of three genes involved in creating beta-diketone—a waxy compound responsible for most of the bluish-grey coating. To confirm their findings, the scientist silenced the newly identified genes using genetic engineering, and showed that seeds from bluish-grey plants grew to become glossy green. They then deciphered the chain of biochemical reactions that leads to beta-diketone synthesis, including the genes and enzymes involved. Next, the scientists repeated the same research with barley, which also has a bluish-grey coating. They found that in barley, the same metabolic gene cluster and biochemical reactions are responsible for the synthesis of beta-diketone as in wheat.
Dr Kostya Kanyuka, plant pathologist at Rothamsted Research, said: “Improving wheat yield, quality and resilience to environmental stresses is one of our Institute’s core strategic research programmes. A few years ago we established a technology called virus-induced gene silencing (or VIGS) to identify wheat genes that defend against fungal pathogens and understand their functions. We were thrilled to use this technology to learn about the wheat genes involved in producing plant surface waxes.”
These findings may one day allow us to breed crops with a higher yield and a greater resistance to drought and pathogens. For instance, it might be possible to introduce the beta-dikotene genes derived from wheat into cucumber or tomato plants. As a result, whatever these plants will lose in brightness, they will gain in sturdiness.
Dr Kanyuka, who leads the wheat functional genomics team, added: “Leaf surface waxes are very important as they reduce water loss and therefore contribute to higher yields during droughts. Moreover, these secondary metabolites represent the first line of defence against pathogens and pests. Although the composition of surface waxes and some of the genes involved in producing them have been known since the early 1960s, molecular understanding of this pathway has remained a mystery until now.”
This project was a collaborative effort between the Weizmann Institute of Science, Tel-Aviv University, the University of British Columbia, and Rothamsted Research and the John Innes Centre, both in the United Kingdom.
- See more at: http://www.rothamsted.ac.uk/news-views/surface-genes-identified-give-wheat-and-barley-their-matte-appearance#sthash.OYIHeMIV.dpuf
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