Pollen that can increase the risk of fungal infection

Does maize pollen give you hayfever?

If so, you may well be reacting to "group-1" allergens — proteins that grass pollen grains secrete. Now it turns out that these proteins may not just be bothersome for you — they may also affect the health of plants on which the pollen lands.

As you might have noticed if you've ever shucked an ear of maize, each kernel (an ovary) has a long silk attached — this is a style. Unpollinated styles remain receptive to pollen for about 8 days before senescing. But a pollinated style senesces once its ovary has been fertilized; this typically occurs a couple of days after pollination.

The quicker a style can be pollinated, the higher the chance of successful seed production, because unpollinated styles are fed on by beetles and other insects. Not only do the insects damage the styles directly, they also vector fungal pathogens that cause smut and ear rot. The fungal spores also gain access to the ovaries by growing through the silk.

So mutations in pollen that cause the pollen tube to grow more slowly towards the ovary might be predicted to increase a maize ear's disease risk.

And this is just what Andy Stephenson and colleagues have found. Pollen tubes from grains that contain a certain mutation in the genes encoding the group-1 proteins grew more slowly than tubes from grains that didn't contain the mutation. Silks pollinated with the mutant pollen senesced later than control silks, and the ears were more likely than control ears to develop fungal diseases.