Female plants accept or reject suitor with help of molecules

October 24th, 2008 - 1:54 pm ICT by IANS  

Washington, Oct 24 (IANS) Plants rely on molecules to accept or reject sex partners like pollen grains and avoid inbreeding. “Unlike an animal’s visual cues about mate selection, a plant’s mate recognition takes place on a molecular level,” said Bruce McClure, associate director of Bond Life Sciences Centre and Missouri University (MU) researcher.

“The pollen (male part) must, in some way, announce to the pistil (female part) its identity, and the pistil must interpret this identity. To do this, proteins from the pollen and proteins from the pistil interact; this determines the acceptance or rejection of individual pollen grains,” he elaborated.

Listening in on this molecular conversation may provide ways to control the spread of transgenes from genetically-modified crops to wild relatives, offer better ways to control fertilisation between cross species and lead to a more efficient way of growing fruit trees.

In the study, researchers used two specific pistil proteins, NaTTS and 120K, as “bait” to see what pollen proteins would bind to them. These two pistil proteins were used because they directly influence the growth of pollen down the pistil to the ovary where fertilisation takes place.

Three proteins, S-RNase-binding protein (SBP1), the protein NaPCCP and an enzyme, bound to the pistil proteins. This action suggests that these proteins likely contribute to the signalling processes that affect the success of pollen growth.

“Our experiment was like putting one side of a Velcro strip on two pistil proteins and then screening a collection of pollen proteins to see which of the pollen proteins have the complementary Velcro strip for binding,” McClure said.

“If it sticks, it’s a good indication that the pollen proteins work with the pistil proteins to determine the success of reproduction,” he added.

In previous studies, McClure showed that S-RNase, a protein on the pistil side, caused rejection of pollen from close relatives by acting as a cytotoxin, or a toxic substance, in the pollen tube, according to a MU press release.

For their study, the MU team used Nicotiana alata, a relative of tobacco commonly grown in home gardens as “flowering tobacco”.

The study appeared in the Journal of Biological Chemistry, co-authored by McClure; Kirby N. Swatek, graduate student; and Christopher B. Lee, post-doctoral researcher at the Bond Life Sciences Center.

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