Scientists identify a gene important for grain quality

Plants produce a protective layer against water loss, excessive solar radiation and pathogens attack; in barley, the genes that contribute to this protective layer are also crucial to produce high quality grain.

Dr Chiara Campoli (IBH and Cell and Molecular Biosciences at The James Hutton Institute)

What is grain skinning and why are we interested in it?

Barley plants protect their grain with a natural “shield” called husk which sticks to the grain surface. However, sometimes the husk can break off either in part or completely, a phenomenon called ‘skinning’. Grain skinning is a serious problem for growers and stakeholders alike, as it leads to poor quality malt.

Barley grains with intact (left) and skinned (right) husk.

We know that growing conditions, such as overly wet or dry spells, can worsen grain skinning. Changes in specific genes can also increases skinning. In the past four years, researchers from the University of Dundee and the James Hutton Institute set out to identify these genes and how they work to control skinning.

Can barley morphological mutants teach us something about grain quality?

To identify genes responsible for grain skinning, we used mutant collections. These are barley plants with genetic differences which show changes in how they grow and develop, for example in flower shape or plant height. Among these are the eceriferum (=waxless) mutants showing a glossy green colour compared to common barley, whose colour is whitish blue-green. This colour difference reflects changes to the cuticle, a protective layer covering all aerial parts of plants which is covered in waxes.

We noticed that some of these glossy cuticle mutants show degrees of grain skinning, from partially skinned to totally husk-less grain. Supported by Biology and Biotechnology Sciences Research Council funding, our research group, led by Sarah McKim and along with Robbie Waugh, Luke Ramsay, Micha Bayer and Chiara Campoli, as well as students, revealed links between cuticle formation and strength of husk adherence to the grain and ultimately to multiple genes responsible for skinning.

One of these genes is called HvGDSL1 which we show is essential both for an intact cuticle and husk to grain adherence.

What does HvGDSL1 do and what all this has to do with grain?

HvGDSL1 makes a protein which produces components that go into the cuticle. Barley plants without normal HvGDSL1 function dry out quickly, showing that these cuticle components help protect barley from water loss. We also found that HvGDSL1 protein works to produce a thick, ridged cuticle over the barley grain, which correlates with husk adhesion. Barley plants with defective HvGDSL1 protein show thinner grain cuticles with fewer ridges resulting in skinned grain. Almost all the 500 barley lines from around the globe we examined showed the same functional HvGDSL1 suggesting that this protein’s function may have played an important role for barley adaptation to dry environments on land.

The whitish blue-green colour of a common barley spike (left) compared to the glossy green colour of a waxless mutant (right).
What’s next?

Many more barley mutants show problems in their cuticles and in husk adherence. We hope that each of them can teach us something about skinning and we are excited to see what else can we learn from them.

If you want to read more in depth about our research, you can find our article at this link:

GDSL-motif Esterase/Lipase Affects Wax and Cutin Deposition and Controls Hull-Caryopsis Attachment in Barley | Plant and Cell Physiology | Oxford Academic (oup.com)

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