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Systematic molecular dissection of Colletotrichum

Tony Lynn Buhr, University of Nebraska - Lincoln

Abstract

The goals of this research were to isolate, clone, and characterize agriculturally relevant genes from the mycoherbicide fungus Colletotrichum gloeosporioides f. sp. aeschynomene and the alfalfa anthracnose fungus C. trifolii. Gene transfer systems are powerful tools utilized for gene characterization and development of an efficient gene transfer system in Colletotrichum was initiated. A $\beta$-tubulin gene TUB2 was cloned from C. gloeosporioides f. sp. aeschynomene and a point mutation in TUB2 was identified and shown to confer a high level of resistance to the anti-microtubule fungicide benomyl. The benomyl-resistant TUB2 allele can be utilized as a selectable marker to examine gene transfer into Colletotrichum. A separate project was to clone a novel protein kinase gene (TB3) from C. trifolii. Environmental surveillance in organisms is coupled to gene expression via signal transduction pathways and kinases are components of signaling pathways that regulate target proteins via phosphorylation. TB3 complemented a colonial mutant of Neurospora crassa showing that a signaling gene required for normal hyphal growth is conserved among pathogenic and saprophytic filamentous fungi. Thus, two Colletotrichum genes were isolated, cloned and initially characterized. However, gene characterization is a continuous, ongoing process. Methodical gene characterization relies on predictable growth and development of organisms under known, specific environmental conditions. A system was developed to characterize gene expression during pre-infection morphogenesis in Colletotrichum since pre-infection morphogenesis is essential for disease initiation and host colonization. Numerous environmental factors were shown to influence (signal) pre-infection morphogenesis, from conidia to germ tubes to appressoria, in C. trifolii and C. gloeosporioides f. sp. aeschynomene including three environmental cues encountered by conidia in nature, self-germination inhibitors, the plant phylloplane polymer cutin and a contact surface. Nearly synchronous morphogenesis of a large C. trifolii conidial population was subsequently used to examine transcription of selected genes, including TUB2 and TB3, during pre-infection morphogenesis, showing that the nearly synchronous morphogenesis system can be utilized for molecular analysis in Colletotrichum.

Subject Area

Molecular biology|Plant pathology|Microbiology|Agronomy

Recommended Citation

Buhr, Tony Lynn, "Systematic molecular dissection of Colletotrichum" (1996). ETD collection for University of Nebraska-Lincoln. AAI9712509.
https://digitalcommons.unl.edu/dissertations/AAI9712509

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