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Identification of novel elicitors from Phytophthora parasitica

Tai-Yu Ke: Natl Taiwan Univ

<div>In response to infection by the pathogens, plants display the first layer of plant immunity, pattern-triggered immunity (PTI), which is elicited upon recognition by plants of microbe-associated molecular patterns originated from elicitors (or apoplastic effectors). To elucidate the mechanisms underlying PTI, it is essential to identify novel elicitors and the corresponding patterns, and furthermore, to find out how these molecules trigger defense response. The aim of this study is to identify novel elicitors from<em> Phytophthora parasitica</em>, a notorious oomyceteous plant pathogen of a wide host range, with special interest in glycoside hydrolases (GHs). Search of the genome database of <em>P. parasitica</em> revealed the presence of a wide array of genes encoding different families of glycoside hydrolases. As a strategy for preliminary screening, we performed quantitative reverse transcriptase-PCR to analyze the expression profiles of candidate genes in the infection process of <em>P. parasitica.</em> Meanwhile, we assessed their elicitor activity by agroinfiltration for transient expression of proteins on <em>Nicotiana</em> <em>benthamiana </em>and<em> Nicotiana tobacum</em> (cv. <em>Samsun</em>-NN). Of the genes analyzed, G_05 and G_07, both contain a GH17 domain, cause severe yellowing symptom, and G_16 containing a GH16 domain causes necrosis on <em>N. tobacum</em>. Genes of GH17 encodes putative beta-1,3-glucanase, whereas the enzymes encoded by GH16 can be diverse. Further analysis by infiltration of recombinant proteins obtained from <em>E. coli</em> indicate that G_16 causes necrosis and reactive oxygen species (ROS) production on the leaves of<em> N. tabacum</em>. These results suggest that G_16 of <em>P. parasitica </em>may encode an elicitor protein.</div>