Analysis of Genes Expressed by Meloidogyne incognita Males: Generation of ESTs and Comparative Genomics

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Title: Analysis of Genes Expressed by Meloidogyne incognita Males: Generation of ESTs and Comparative Genomics
Author: Snyder, Daniel Watchorn
Advisors: Charles H. Opperman, Committee Co-Chair
Jeffrey Thorne, Committee Member
David Mckenzie Bird, Committee Chair
Abstract: Over the last decade genomic and molecular research in model systems including Ceanorahbditis elegans have generated a body of knowledge that has revolutionized the study of plant parasitic nematode biology and disease. Meloidogyne incognita is one of the most devastating plant parasitic nematodes worldwide and has proven to be a prime example of the utility of comparative genomics in the investigation of plant diseases. The role of males and sex determination in this species presents a particularly interesting evolutionary and biological issue but is poorly understood at the molecular level. A method for generating and collecting male M. incognita tissue that is free of other life stages or females and other contaminating organisms was developed. The method confirmed previous results that host-pruning stress stimulates male sex differentiation and that the effects of this stimulus are limited to the time period of early second stage larvae feeding. Approximately 5,000 ESTs were generated by 5' sequencing of cDNAs from four male M. incognita libraries constructed from the tissue obtained above. Two cDNA libraries were constructed by utilizing a nematode splice leader (SL1) and two libraries were constructed with a universal template switch method. The ESTs from these libraries were clustered for each library and as a complete set from all four libraries providing insight to the composition and abundance of genes expressed by these males. Searching the public databases for homologous sequences providing a second degree of clustering and provided the putative identification of genes identified by these clusters. Approximately 89% of the clusters had significant homology to the public databases and approximately 31% of these had homology to C. elegans. Additional annotation of these genes was conducted using several public resources providing further insight to the molecular basis of male M. incognita biology and comparative analyses to other stages and nematode species. Protein phosphatases, transthyretin-like families and major sperm proteins are some of the most abundant sequences in these male libraries and are also highly expressed in C. elegans males. These results indicate that not only are these M. incognita libraries representative of male gene expression, but that male gene expression profiles may be similar across families.
Date: 2004-07-21
Degree: MS
Discipline: Plant Pathology

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