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The Root-Knot Nematode Calreticulin Mi-CRT Is a Key Effector in Plant Defense Suppression

January 2013 , Volume 26 , Number  1
Pages  97 - 105

M. Jaouannet,1,2,3 M. Magliano,1,2,3 M. J. Arguel,1,2,3 M. Gourgues,1,2,3 E. Evangelisti,1,2,3 P. Abad,1,2,3 and M. N. Rosso1,2,3

1INRA, UMR 1355 Institut Sophia Agrobiotech, 2Université de Nice Sophia Antipolis, UMR Institut Sophia Agrobiotech, and 3CNRS, UMR 7254 Institut Sophia Agrobiotech, 400 route des Chappes F-06903 Sophia Antipolis, France

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Accepted 24 July 2012.

Root-knot nematodes (RKN) are obligate biotrophic parasites that settle close to the vascular tissues in roots, where they induce the differentiation of specialized feeding cells and maintain a compatible interaction for 3 to 8 weeks. Transcriptome analyses of the plant response to parasitic infection have shown that plant defenses are strictly controlled during the interaction. This suggests that, similar to other pathogens, RKN secrete effectors that suppress host defenses. We show here that Mi-CRT, a calreticulin (CRT) secreted by the nematode into the apoplasm of infected tissues, plays an important role in infection success, because Mi-CRT knockdown by RNA interference affected the ability of the nematodes to infect plants. Stably transformed Arabidopsis thaliana plants producing the secreted form of Mi-CRT were more susceptible to nematode infection than wild-type plants. They were also more susceptible to infection with another root pathogen, the oomycete Phytophthora parasitica. Mi-CRT overexpression in A. thaliana suppressed the induction of defense marker genes and callose deposition after treatment with the pathogen-associated molecular pattern elf18. Our results show that Mi-CRT secreted in the apoplasm by the nematode has a role in the suppression of plant basal defenses during the interaction.

© 2013 The American Phytopathological Society