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This release is available in German . IMAGE: These are thale cress ( Arabidopsis thaliana I ) plants with powdery mildew infection. The white coating on the infected leaves, which originates from the mycelium on the leaf surface, is really a typical Click here for far more information. Mildew infections not only cause unsightly vegetable patches, they can also result in extensive crop failure. Interestingly, the processes involved in infections with this garden pest are comparable to those involved in fertilisation. Scientists from the Max Planck Institute for Plant Breeding Research in Cologne as well as the University of Zurich have identified two proteins within the model plant species Arabidopsis thaliana that are crucial for both fertilisation and infection with powdery mildew. This explains why mildew-resistant plants, in which these genes are mutated, are infertile. ( Science , Vol 330, p 968-971) Pollen tubes and hyphae, the filamentous structures of which fungi are formed, not only look pretty similar, they also require similar proteins. The two proteins in question, which have just been discovered, are named after the Etruscan fertility goddesses Feronia and Nortia. The scientists discovered that these proteins are both beneficial and harmful to plants. They link the capacity for seed formation with the absence of resistance to mildew infection. Feronia signals to the pollen tube, which germinates from the pollen, that it has reached its destination and that it's time to release the male gametes. The protein is also formed in the leaves, however, and gives mildew with access to the plant. For the latter to turn into resistant to the intruder, both the maternal and paternal copies of the feronia gene need to be defective. If the plant lacks the feronia protein, however, the pollen tube doesn't stop growing at the entrance to the embryo sac but continues to penetrate into the female component of the flower and doesn't trigger the release of sperm cells. As a result, fertilisation does not take place and an embryo does not develop. The protein Nortia is also involved in fertilisation; however, it doesn't occur inside the leaves. A protein recognized as MLO, which is closely related to Nortia, is discovered there instead. MLO makes plants, e.g. barley, in which Ralph Panstruga discovered the MLO gene a couple of years ago, prone to mildew. However, they only turn into resistant if both copies of the MLO gene are mutated. Because Arabidopsis has 3 MLO genes that play a role in susceptibility to mildew, in this plant, six copies should turn out to be defunct just before it becomes resistant to mildew. Numerous other genes exist, however, that also cause resistance to fungal infections in plants. Resistant or fertile Feronia and Nortia are formed by the helper cells of the embryo sac. They bring about the fusion of the gametes in the ovary. Feronia and MLO inside the leaves allow mildew to penetrate into the plant. This dual function indicates why evolution has not yet succeeded in blocking this point of access to mildew. It would clearly be incredibly difficult to decouple these two functions. Therefore, the alternatives are: resistant and infertile, or vulnerable and fertile, says Ralph Panstruga from the Max Planck Institute for Plant Breeding Research. Feronia is a receptor that apparently directly influences Nortia. However, the scientists don't yet know how Feronia cooperates with Nortia and MLO. Our goal would be to breed mildew-resistant plants based on Feronia mutants which are also fertile, says Panstruga. This is really a incredibly ambitious aim, as evolution appears not to have produced any such mutants up to now. Feronia evidently plays such an important role within the ovary as well as the leaves that the plant just cannot manage without it. ### Original work: Sharon A. Kessler, Hiroko Shimosato-Asano, Nana F. Keinath, Samuel E. Wuest, Gwyneth Ingram, Ralph Panstruga and Ueli Grossniklaus Conserved Molecular Components for Pollen Tube Reception and Fungal Invasion Science , 12 November 2010, 330: 968-971
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