Analysis of Magnaporthe Oryzae Homologs of Histoplasma Capsulatum RYP Genes

Persistent Link:
http://hdl.handle.net/10150/293639
Title:
Analysis of Magnaporthe Oryzae Homologs of Histoplasma Capsulatum RYP Genes
Author:
Wickramage, Amritha Suhasini
Issue Date:
2013
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The ascomycete fungus Magnaporthe oryzae, causative agent of rice blast disease, poses a threat to global food security, destroying enough rice to feed 60 million people each year. Characterization of the host-pathogen interaction between rice and M. oryzae is critical, as better understanding of the system may lead to better disease control strategies. The sequenced genome and repertoire of molecular tools available have made M. oryzae an ideal model system for understanding general plant-pathogen interactions as well. The objective of this dissertation was to characterize the M. oryzae homologs of Histoplasma capsulatum RYP (Required for Yeast Phase) genes that are required for transition to the parasitic phase. H. capsulatum is a human pathogen that undergoes a dimorphic switch from filamentous to yeast cell growth at 37°C, the host body temperature. Four H. capsulatum RYP genes were identified in a forward genetic screen to identify genes required for entry into the yeast phase. RYP1 is a member of the Gti1_Pac2 family, which contains previously characterized regulators of dimorphic switching. RYP2 and RYP3 are homologs of vosA and velB, members of the Velvet family, best characterized in Aspergillus nidulans, where they coordinate morphological differentiation with secondary metabolism. RYP4 is a zinc binuclear cluster protein, a main class in the zinc finger transcription factor family. Deletion of the M. oryzae RYP1 homolog, RIG1 (Required for Infectious Growth), resulted in a non-pathogenic mutant on susceptible rice cultivars, even upon removal of the host penetration barrier. Δrig1 was blocked in the transition to infectious hyphal growth, similar to H. capsulatum ryp1, which could not transition to the yeast phase. Deletion mutants of M. oryzae RYP2, RYP3, and RYP4 homologs were similar to the wild type in somatic growth and pathogenicity indicating that although RIG1 is a pathogenicity factor conserved in plant and animal pathogens, such conservation does not apply to all of the RYP pathogenicity genes identified in H. capsulatum. Δrig1 is the first M. oryzae mutant known to be blocked in production of primary infection hyphae. Overall, the study suggests limited parallels exist in phase transition of fungal pathogens of plants and animals.
Type:
text; Electronic Dissertation
Keywords:
Magnaporthe oryzae; RIG1; Plant Science; Gti1_Pac2 family
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Plant Science
Degree Grantor:
University of Arizona
Advisor:
Orbach, Marc J.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleAnalysis of Magnaporthe Oryzae Homologs of Histoplasma Capsulatum RYP Genesen_US
dc.creatorWickramage, Amritha Suhasinien_US
dc.contributor.authorWickramage, Amritha Suhasinien_US
dc.date.issued2013-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe ascomycete fungus Magnaporthe oryzae, causative agent of rice blast disease, poses a threat to global food security, destroying enough rice to feed 60 million people each year. Characterization of the host-pathogen interaction between rice and M. oryzae is critical, as better understanding of the system may lead to better disease control strategies. The sequenced genome and repertoire of molecular tools available have made M. oryzae an ideal model system for understanding general plant-pathogen interactions as well. The objective of this dissertation was to characterize the M. oryzae homologs of Histoplasma capsulatum RYP (Required for Yeast Phase) genes that are required for transition to the parasitic phase. H. capsulatum is a human pathogen that undergoes a dimorphic switch from filamentous to yeast cell growth at 37°C, the host body temperature. Four H. capsulatum RYP genes were identified in a forward genetic screen to identify genes required for entry into the yeast phase. RYP1 is a member of the Gti1_Pac2 family, which contains previously characterized regulators of dimorphic switching. RYP2 and RYP3 are homologs of vosA and velB, members of the Velvet family, best characterized in Aspergillus nidulans, where they coordinate morphological differentiation with secondary metabolism. RYP4 is a zinc binuclear cluster protein, a main class in the zinc finger transcription factor family. Deletion of the M. oryzae RYP1 homolog, RIG1 (Required for Infectious Growth), resulted in a non-pathogenic mutant on susceptible rice cultivars, even upon removal of the host penetration barrier. Δrig1 was blocked in the transition to infectious hyphal growth, similar to H. capsulatum ryp1, which could not transition to the yeast phase. Deletion mutants of M. oryzae RYP2, RYP3, and RYP4 homologs were similar to the wild type in somatic growth and pathogenicity indicating that although RIG1 is a pathogenicity factor conserved in plant and animal pathogens, such conservation does not apply to all of the RYP pathogenicity genes identified in H. capsulatum. Δrig1 is the first M. oryzae mutant known to be blocked in production of primary infection hyphae. Overall, the study suggests limited parallels exist in phase transition of fungal pathogens of plants and animals.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectMagnaporthe oryzaeen_US
dc.subjectRIG1en_US
dc.subjectPlant Scienceen_US
dc.subjectGti1_Pac2 familyen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePlant Scienceen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorOrbach, Marc J.en_US
dc.contributor.committeememberVanEtten, Hans D.en_US
dc.contributor.committeememberCotty, Peter J.en_US
dc.contributor.committeememberTax, Frans E.en_US
dc.contributor.committeememberPalanivelu, Ravishankaren_US
dc.contributor.committeememberOrbach, Marc J.en_US
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