Companion Cell Protects Sperms from Genetic Damage

Scientists at Instituto Gulbenkian de Ciência (IGC), in Portugal, and Cold Spring Harbor Laboratory, in New York, have described the mechanism by which plants prevent transposons-caused mutation from occurring in pollen grains.

Transposons or jumping genes are very common in all known genomes. For instance, transposons make up more than 70 percent of the maize genome. Activation of transposons may lead to deleterious mutations, and thus it needs to be under tight control. If such harmful mutations occur in sexual cells, they will be transmitted to the progeny and spread in the population.

In pollen grains, sperm cells are protected by large companion cells. The companion cell provides the sperm with energy and nourishment, and pushes them towards their targets during fertilization. The scientists found that companion cell also provide the sperm cells with instructions that protect their DNA from damage and thus help pass on a stable genome to the next generation. The instruction is in the form of small interfering RNAs (siRNA), molecules that silence transposons via RNA interference.

For more information, read http://www.igc.gulbenkian.pt/media/article/39 The paper published by Cell is available at http://www.cell.com/abstract/S0092-8674(08)01644-9