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A Profile of Putative Parasitism Genes Expressed in the Esophageal Gland Cells of the Root-knot Nematode Meloidogyne incognita

May 2003 , Volume 16 , Number  5
Pages  376 - 381

Guozhong Huang , 1 Bingli Gao , 1 Tom Maier , 2 R. Allen , 1 Eric L. Davis , 3 Thomas J. Baum , 2 and Richard S. Hussey 1

1Department of Plant Pathology, University of Georgia, Athens 30602-7274, U.S.A.; 2Department of Plant Pathology, Iowa State University, 351 Bessey Hall, Ames 50011, U.S.A.; 3Department of Plant Pathology, North Carolina State University, Box 7616, Raleigh 27695-7616, U.S.A.

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Accepted 12 January 2003.

Identifying parasitism genes encoding proteins secreted from a nematode's esophageal gland cells and injected through its stylet into plant tissue is the key to understanding the molecular basis of nematode parasitism of plants. Meloidogyne incognita parasitism genes were cloned by microaspirating the cytoplasm from the esophageal gland cells of different parasitic stages to provide mRNA to create a gland cell-specific cDNA library by long-distance reverse-transcriptase polymerase chain reaction. Of 2,452 cDNA clones sequenced, deduced protein sequences of 185 cDNAs had a signal peptide for secretion and, thus, could have a role in root-knot nematode parasitism of plants. High-throughput in situ hybridization with cDNA clones encoding signal peptides resulted in probes of 37 unique clones specifically hybridizing to transcripts accumulating within the subventral (13 clones) or dorsal (24 clones) esophageal gland cells of M. incognita. In BLASTP analyses, 73% of the predicted proteins were novel proteins. Those with similarities to known proteins included a pectate lyase, acid phosphatase, and hypothetical proteins from other organisms. Our cell-specific analysis of genes encoding secretory proteins provided, for the first time, a profile of putative parasitism genes expressed in the M. incognita esophageal gland cells throughout the parasitic cycle.

Additional keywords: gland-cell cDNA library, plant-parasitic nematode, stylet secretions.

© 2003 The American Phytopathological Society