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SHATTERPROOF genes in Arabidopsis are good news for agriculture
By Bijal P. Trivedi

A closed seedpod. Arrow shows where pod splits.

A seedpod after splitting.

In a plant with mutant versions of the two SHATTERPROOF genes the seedpod fails to split.

Crops can be improved in a surprising number of ways, and tweaking genes to improve yield is just one. Twenty to fifty percent of a rapeseed crop, harvested and crushed to yield canola oil, can be lost because the pods open and release the seeds before the farmer can harvest them. But when two nifty genes called SHATTERPROOF1 (SHP1) and SHATTERPROOF2 (SHP2) are mutated, the seed pods fail to shatter, or burst. The ideal situation for the farmer would be to delay pod shattering until the crop has been harvested. The recent discovery of weakened versions of SHP1 and SHP2 that work less efficiently may be just the thing.

“The seedpod is just like a small pea pod that is glued together at the seam with a cell-secreted chemical called pectin,” says Martin Yanofsky, of the University of California, San Diego. When the seedpod or fruit matures, two critical changes happen. Some cells secrete pectinases that degrade the glue, while other cells near the seam shrink, becoming dry, woody and taut, creating a “coiled spring” type mechanism that flings the seeds out of the pod. When the “glue” is gone, the pod bursts open, spraying the seeds around the plant.

In this week’s issue of Nature, the Yanofsky team reports the discovery of two weakened SHATTERPROOF genes in Arabidopsis thaliana, a tiny flowering weed geneticists study to isolate genes important in plant development. Genes that control pod shattering in Arabidopsis are likely to be present in close relatives like cauliflower, broccoli, Brussels sprouts, peas, soy beans and other important food crops.

Finding weak versions of SHATTERPROOF and inserting them into rapeseed might increase the production of crop per hectare, making the land more productive and reducing the amount of water, pesticides and fertilizer a farmer needs, says Yanofsky. It might be one of the more immediate applications of the team’s discovery.

See related GNN article
»What Makes Plants Grow?

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Liljegren, S.J. et al. SHATTERPROOF MADS-box genes control dispersal in Arabidopsis. Nature 404, 766-770 (April 13, 2000).

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