The pollen from some plants can cause allergic rhinitis, a.k.a., “hay fever” in many people. This is because, when the pollen is inhaled into the nasal passages, antigens on the surface of the pollen elicit an immune response in people with a sensitized immune system. (In grass pollen, the allergens may be so-called “expansins”, which are proteins involved in plant cell growth – but that is a story for another time.)
In flowering plants, the pollen is produced by the stamens, or, more precisely, the anthers at the tips of the stamens (see photo below). The anthers are the male reproductive parts of the flower because the pollen grains contain sperm cells.
What’s a plant-lover with pollen allergies to do?
One thing might be to cultivate mostly female plants in your yard as described in the book Allergy-Free Gardening: The Revolutionary Guide to Healthy Landscaping. (Listen to an interview with the author on NPR here.)
Another way would be to produce flowering plants that don’t make pollen.
This is indeed what some scientists in Spain have done, as reported in the 31 August 2012 online edition of the open-access journal BioMedCentral Plant Biology (see reference 1 below).
Briefly, these scientists developed techniques using Agrobacterium to genetically transform some plants in the genus Pelargonium (more commonly known as geraniums, which have considerable economic importance in the ornamental plant market).
These genetically engineered (GE) plants express a bacterial gene coding for barnase, an enzyme that breaks down RNA, which usually would be lethal. But these researchers designed the barnase gene so that it would only be expressed in the anthers. Thus, anther development in these GE geraniums was severely inhibited, and no pollen grains were observed. Otherwise, the flowers looked normal.
Other than producing allergen-free flowers, why would anyone want plants that don’t produce pollen, that is, that are male-sterile?
The use of male-sterile GE plants is considered more “environmentally friendly” because of the prevention of gene flow between the GE plants and related plant species through cross-pollination.
For another thing, male-sterility greatly facilitates the production of hybrid plants, that is, plants that result from the genetic crossing of two genetically distinct parents.
Plant hybrids “…are often created by humans in order to produce improved plants. These improvements can include the production of more or improved; seeds, fruits or other plant parts for consumption, or to make a plant more winter or heat hardy or improve its growth and/or appearance for use in horticulture. Much work is now being done with hybrids to produce more disease resistant plants for both agricultural and horticultural crops. In many groups of plants hybridization has been used to produce larger and more showy flowers and new flower colors.” (from: Wikipedia)
By the way, besides being male-sterile, another feature of the GE geraniums reported in Ref. 1 below is that these plants lived longer than normal geraniums. Next time I’ll explore how they did that by adding just one gene.
1. Begoña G.-S., et al. (2012) “Production of engineered long-life and male sterile Pelargonium plants.” BMC Plant Biology, Published Online: 31 August 2012. (Abstract)
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