How does inbreeding avoidance evolve in plants?

Jun 10, 2013

Inbreeding is generally deleterious, even in flowering plants. Since inbreeding raises the risk that bad copies of a gene will be expressed, inbred progeny suffer from reduced viability.

Many are able to recognize and reject their own pollen, thereby preventing inbreeding despite the plants' hermaphroditic nature. This mechanism is a complex trait that involves the interaction of a gene that tags the pollen with an identifier molecule, and a gene that produces a molecule capable of detecting pollen produced by the same plant.

have often argued that once complex traits are lost, they are seldom regained. But a new study, led by biologists at McGill University and published in the journal PLOS Biology, suggests that this may not be the case for self-pollen recognition.

In the leading to the genus Leavenworthia (a plant group related to and cole crops such as broccoli and cabbage), the ancestral genes that code for self-pollen recognition were lost. But the self-pollen recognition function in Leavenworthia appears to have been taken up by two other genes that originally may have had a different role—for example, in pathogen recognition.

"Self-incompatibility," the pollen- that enables plants to avoid the inbreeding caused by self-pollination, involves a pair of tightly linked genes known as the S locus. In this study, the researchers analyzed the , genome organization, and gene of S loci in members of the Brassicaceae family, which includes plants of the genus Leavenworthia.

"We conclude that both genes that comprise the ancestral S locus in the Brassicaceae were lost in Leavenworthia," says McGill researcher Sier-Ching Chantha, lead author of the study. Our analyses show, however, that plants of this genus have two other linked genes that exhibit patterns characteristic of an S locus. These genes occupy the same genomic position in Leavenworthia as do two non-S-locus genes in a related species. We suggest that these genes have evolved to assume the function of the pollen recognition system of self-incompatibility in Leavenworthia."

How plants avoid , and the related topic of S locus evolution have been important research subjects for plant biologists. There can be hundreds of variants of a single S-locus in individual plant populations—a very unusual situation. In the animal world, a similar pheomenon is the many variations in immune-system genes. Immune system genes in animals, like the S locus in plants, are also involved in recognition, though in the case of immune genes it is foreign antigens rather than pollen types that are recognized. It seems that the recognition function can act in both systems to allow the evolution of large amounts of genetic diversity.

"François Jacob, the famous French biologist, once compared the action of natural selection to that of a tinkerer who uses the materials around him to produce a working object," notes McGill biology professor Daniel Schoen, the corresponding author of the study. "The evolution of the genes involved in self-pollen recognition in Leavenworthia provides a compelling example of this idea, and lends credence to the notion that the loss of complex traits may not always be irreversible."

Explore further: How hummingbirds evolved to detect sweetness

More information: www.plosbiology.org/article/in… journal.pbio.1001560

add to favorites email to friend print save as pdf

Related Stories

Mate choice in plants

Jun 28, 2008

In flowering plants, the female reproductive organ, the pistil, comprises the stigma, style, and ovary. The stigma catches pollen shed by the male anthers. If the pollen is compatible, it will germinate and send tubes through ...

Gatekeeper for tomato pollination identified

Dec 23, 2010

Tomato plants use similar biochemical mechanisms to reject pollen from their own flowers as well as pollen from foreign but related plant species, thus guarding against both inbreeding and cross-species hybridization, report ...

No more sneezing, allergen free house plants

Aug 31, 2012

New research published in BioMed Central's open access journal BMC Plant Biology shows how targeting two bacterial genes into an ornamental plant (Pelargonium), can produce long-lived and pollen-free plants. ...

Tracking Genes for Self-pollination in Arabidopsis

Apr 27, 2007

Some plants need a partner to reproduce. Pollen from one plant pollinates the stigma of another, and a seed is formed. But other plants can self-pollinate, a handy survival mechanism for a lonely plant.

Recommended for you

Neutering project curbed feral cat population

27 minutes ago

(HealthDay)—An intensive effort to sterilize feral cats reduced the number of felines taken to an animal shelter in Florida and euthanized, a new study reveals.

Researchers look at small RNA pathways in maize tassels

8 hours ago

Researchers at the University of Delaware and other institutions across the country have been awarded a four-year, $6.5 million National Science Foundation grant to analyze developmental events in maize anthers ...

How plant cell compartments change with cell growth

8 hours ago

A research team led by Kiminori Toyooka from the RIKEN Center for Sustainable Resource Science has developed a sophisticated microscopy technique that for the first time captures the detailed movement of ...

Plants can 'switch off' virus DNA

9 hours ago

A team of virologists and plant geneticists at Wageningen UR has demonstrated that when tomato plants contain Ty-1 resistance to the important Tomato yellow leaf curl virus (TYLCV), parts of the virus DNA ...

User comments : 0