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Functional characterization of a large group of CLE effectors encoded by Globodera cyst nematodes

Shiyan Chen: School of Integrative Plant Science, Cornell University

<div>Like other biotrophic pathogens, plant-parasitic nematodes secrete various effector proteins into host plant cells to facilitate successful infection. <em>CLAVATA3/ESR (CLE)</em>-like effector genes are expressed in various cyst nematode species and their encoded proteins function as mimics of plant CLE peptides to modulate plant developmental pathways that promote the formation of feeding cells needed for the feeding nematode. We previously cloned a large group of CLE genes from four closely related <em>Globodera</em> species, including <em>G. rostochiensis</em>, <em>G. pallida</em>, <em>G. ellingtonae</em> and <em>G. tabacum</em>. These <em>Globodera</em> <em>CLE</em> genes were found to encode predominantly multiple-domain CLE proteins that may result in 37 unique CLE peptides when proteolytically processed <em>in planta</em>. <em>Globodera</em> CLE peptides can be grouped in two classes based on root phenotypes observed in the <em>in vitro</em> peptide application assay: one that suppresses root growth (Group I) and the other that does not arrest root growth (group II). Microscopic observations indicated that several Group II peptides may have an effect in root vasculature. In addition to the StCLV2 receptor, StRPK2, an orthologue of the <em>Arabidopsis</em> RPK2 receptor, was also found to be involved in perceiving PCN-secreted CLE peptides to facilitate nematode parasitism. Further studies are underway to identify other candidate host receptors that are targeted by this large group of nematode-secreted CLE peptides.</div>