Investigating phytopathogen putative effector proteins that target starch granule initiation

Jones, Sally Louise (2023) Investigating phytopathogen putative effector proteins that target starch granule initiation. Doctoral thesis, University of East Anglia.

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The chloroplast is a key target of pathogen effectors. Two putative effector proteins, ChEC153 and HaRxL94b from Colletotrichum higginsianum and Hyaloperonospora arabidopsidis, respectively, localise to discrete, chloroplastic puncta when expressed in N. benthamiana. These punctate sub-chloroplastic localisations are remarkably similar to those of several proteins involved in the initiation of starch granules. I thereby sought to evaluate the putative effectors in the context of starch granule initiation, observing both to co-localise with key starch granule initiation protein MYOSIN-RESEMBLING CHLOROPLAST PROTEIN (MRC). Further, ChEC153 expression in planta induces the formation of small starch granules.

I evaluated the role of ChEC153 in infection, finding that expression of the putative effector increases host susceptibility to C. higginsianum. Additionally, I found that mrc mutants have increased resistance to infection, pointing to the potential for starch granule initiation to play a role in host susceptibility. I identified CRBIC (AT1G53120) as a potential host interactor of ChEC153 through immunoprecipitation-mass spectrometry, and found it was recruited to ChEC153-puncta during co-expression, supporting their interaction.

Following publication of an alternative gene model for ChEC153, I experimentally determined the true gene model: ChEC153.3. I also employed dual-transcriptomic analysis of Arabidopsis infected with C. higginsianum strains with and without ChEC153.3 present to probe processes targeted by the putative effector in either the host or pathogen, identifying a number of genes differentially expressed between the two infections. These genes point to the importance of ChEC153.3 in infection, and support a carbohydrate-targeting role for the putative effector.

In addition to investigating the two putative effector proteins, this thesis highlights new links between starch granule initiation and infection, as well as suggesting associations between the sites of starch granule initiation and plastidial transcription.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Nicola Veasy
Date Deposited: 29 May 2024 11:16
Last Modified: 29 May 2024 11:20


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