Denghui Xing

Document Type

Thesis - University Access Only

Award Date

2002

Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology

Abstract

To understand the molecular events during the pathogenesis of Fusariwn head blight (FHB) in wheat (Triticum aestivum L.), the gene expression profiles of resistant cultivar Swnai 3 and susceptible cultivar Wheaton were investigated. The expressed sequence tags (EST) of four treatments (Fusarium-inoculated Sumai 3, Fusariuminoculated Wheaton, water-inoculated Swnai 3 and water-inoculated Wheaton) were first revealed with DDRT-PCR and then compared. Five ESTs specifically expressed in Fusarium-inoculated Sumai 3 were identified, cloned and sequenced. Southern and Northern analyses indicated that the cognate genes of ESTs A 7 and G 12 belonged to the host wheat, the cognate genes of ES Ts C4 and C7 to the pathogen Fusarium graminearum. As to the cognate gene of EST G75, its identity cannot be defined by the hybridization analyses. Three cognate full-length cDNAs of C4 and one of G 12 were further isolated with 5' rapid amplification of cDNA ends (RACE) technique, cloned and sequenced. The corresponding full-length cDNAs of C4 and G 12 were assembled by combining the sequences of C4 and G 12 with their cognate 5' end sequences. The sequence analysis of cognate full-length cDNA of C4 indicated that these cDNAs code a ACBP (long chain acyl-coA binding protein)-like protein. Long chain acyl-coA (LCA) esters are a key regulator of fatty acid synthesis and affect a large number of cellular systems and functions including gene regulation. The putative ACBP-like protein might have a role in FHB pathogenesis by LCA-mediated expression regulation of F graminearum genes. The similarity analysis by searching the est database of GenBank revealed several cDNAs, which derived from the F graminearum-infected wheat and barley and over-expressed F. sporotrichioides cDNA library, to be similar to the cognate full-length cDNAs of C4. These similar sequences provide further evidence that C4 belonged to F graminearum. Sequence analysis of the full-length cDNA of 012, 012-S, indicated that G 12-S represents a non-coding RNA. Similarity analyses by searching the nr and est database of GenBank revealed that the sequence of G 12-S is similar to the minus strands of two genes, three cDNAs and one EST. The two genes are chloroplast genes of wheat and barley encoding ATP synthase CF-0 subunit I. The similar cDNAs and EST came from the pathogen-infected Sorghum bicolor and the salt-stressed barley. The gene represented by 012-S may regulate Sumai 3's resistance to FHB by directly targeting the gene transcripts of chloroplast ATP synthesis CF-0 subunit I and/or its likes and neutralizing their ability to translation.

Library of Congress Subject Headings

Wheat -- Disease and pest resistance -- Genetic aspects Fusarium diseases of plants

Format

application/pdf

Number of Pages

83

Publisher

South Dakota State University

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