Characterization of cell surface modifications that enable the apple scab fungus, Venturia inaequalis, to differentiate and maintain infection structures during host colonization

Filamentous fungi are amongst the most destructive and economically relevant pathogens of plants worldwide. Crucial to their success as pathogens, is their ability to switch between cellular morphotypes during host infection, with key roles defined in host entry and nutrient acquisition, as well as in the delivery of effector proteins that manipulate host physiology and immunity to promote colonization. Relatively little is known about modifications to the fungal cell surface that enable these organisms to differentiate and maintain infection-related cellular morphotypes during colonization of the hostile host interior. The aim of this project is to provide a better understanding of these modifications, using the apple scab fungus, Venturia inaequalis, as a model.

V. inaequalis undergoes dramatic changes in cellular morphology that permit colonization of the extracellular space located between the cuticle and epidermal cells of apple leaves and fruit (Bowen et al. 2011; Kucheryava et al. 2008). These changes include the differentiation of subcuticular runner hyphae and stromata. Subcuticular runner hyphae are much wider in diameter than regular tubular hyphae found on the plant surface or in culture, and are often fused along their lengths to form ‘hyphal superhighways’. This longitudinal fusion is never observed in regular tubular hyphae. Stromata are made up of single or multiple layers of pseudoparenchyma, a cell type that results from a switch in the polarity of cell division (i.e. from polar tip extension to non polar lateral division). Stromata are presumably required for nutrient acquisition and effector delivery, but also give rise to spores that further the pathogen’s infection cycle. Strikingly, V. inaequalis undergoes similar dramatic changes in morphology in the absence of the host, inside cellophane membranes. Only upon exiting the cellophane membrane is the fungus able to switch back to regular tubular hyphal growth. As V. inaequalis can differentiate similar cellular morphotypes in both a host and an artificial host environment, this fungus represents an ideal model for dissecting how filamentous plant-pathogenic fungi, through changes in their cell surface, differentiate and maintain infection-related cellular morphotypes essential to host colonization.

The project has five objectives:

1. To characterize the sequence of cellular events associated with the morphological differentiation of different cellular morphotypes.
2. To characterize the cell wall carbohydrate and protein composition of different cellular morphotypes.
3. To characterize the secreted protein composition of different cellular morphotypes.
4. To characterize the gene expression profiles of different cellular morphotypes.
5. To functionally characterize genes associated with the morphological differentiation of different cellular morphotypes.

Techniques used in the research: cloning, live-cell imaging, confocal laser scanning microscopy, bright field/epifluorescence microscopy, gas chromatography/electron ionization–mass spectrometry, liquid chromatography–tandem mass spectrometry, laser-capture microdissection, RNA-Seq transcriptome sequencing, reverse-transcription quantitative real-time PCR, bioinformatics, gene disruption/deletion/overexpression.

Applicants should have a strong interest in molecular plant–microbe interactions, and hold a first or upper second class B.Sc.(Hons) or M.Sc. degree in Molecular Plant Pathology, Plant Molecular Biology, Molecular Microbiology, Genetics, or a related discipline. Experience in microscopy, plant pathology, fungal biology, proteomics, and genomics/transcriptomics would be an advantage.

Massey University is a leading New Zealand University for postgraduate study, and is one of the QS-ranked top 30 universities in the world for Agriculture. Palmerston North is a small, student-centered city with a vast range of recreational opportunities.

The scheduled start date for the project is 2018. To apply, please send the following to Dr Carl Mesarich (Primary Supervisor; [Email Address Removed]) before the closing date:
• Curriculum vitae
• Motivation letter
• Contact details of at least two academic referees (preferably email addresses)
• Copy of English Language certificate (if English is not your first language)
• Copy of undergraduate and postgraduate academic transcripts

Shortlisted applicants will be interviewed by Skype. Informal inquiries can be directed to Dr Carl Mesarich ([Email Address Removed]).

Applicants must meet Massey University admission requirements:
http://www.massey.ac.nz/massey/admission/enrolment/entry-requirements/entry-requirements_home.cfm

Minimum English requirements for international applicants are detailed at: http://www.massey.ac.nz/massey/international/study-with-massey/entry-requirements/entry-requirements_home.cfm

For general enquiries about international admissions please contact the International Office ([Email Address Removed]).

Further information on postgraduate study at Massey University can be found at:
http://www.massey.ac.nz/massey/postgraduate/postgraduate_home.cfm

Molecular Plant Pathology Laboratory: http://www.massey.ac.nz/massey/learning/colleges/college-of-sciences/research/agriculture-environment-research/agriculture/molecular-plant-pathology-lab/molecular-plant-pathology-lab_home.cfm