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In Planta Study Localizes an Effector Candidate from Austropuccinia psidii Strain MF-1 to the Nucleus and
Carolina Alessandra de Almeida Hayashibara1, Mariana da Silva Lopes1, Peri A Tobias2
1Department of Genetics, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Piracicaba 13418-900, SP, Brazil.
Abstract:
Austropuccinia psidii is a biotrophic fungus that causes myrtle rust. First described in Brazil, it has since spread to become a globally important pathogen that infects more than 480 myrtaceous species. One of the most important commercial crops affected by A. psidii is eucalypt, a widely grown forestry tree. The A. psidii-Eucalyptus spp. interaction is poorly understood, but pathogenesis is likely driven by pathogen-secreted effector molecules. Here, we identified and characterized a total of 255 virulence effector candidates using a genome assembly of A. psidii strain MF-1, which was recovered from Eucalyptus grandis in Brazil. We show that the expression of seven effector candidate genes is modulated by cell wax from leaves sourced from resistant and susceptible hosts. Two effector candidates with different subcellular localization predictions, and with specific gene expression profiles, were transiently expressed with GFP-fusions in Nicotiana benthamiana leaves. Interestingly, we observed the accumulation of an effector candidate, Ap28303, which was upregulated under cell wax from rust susceptible E. grandis and described as a peptidase inhibitor I9 domain-containing protein in the nucleus. This was in accordance with in silico analyses. Few studies have characterized nuclear effectors. Our findings open new perspectives on the study of A. psidii-Eucalyptus interactions by providing a potential entry point to understand how the pathogen manipulates its hosts in modulating physiology, structure, or function with effector proteins.
Insights
Austropuccinia psidii causes myrtle rust in eucalypts. Researchers identified 255 effector candidates, finding one nuclear effector, Ap28303, that may manipulate host functions.
Area of Science:
- Plant Pathology
- Molecular Biology
- Genomics
Background:
- Austropuccinia psidii (myrtle rust) is a significant pathogen of over 480 myrtaceous species, including commercially important eucalypts.
- The molecular mechanisms of A. psidii pathogenesis in Eucalyptus spp. are not well understood, but are likely mediated by secreted effector molecules.
Purpose of the Study:
- To identify and characterize virulence effector candidates in A. psidii infecting Eucalyptus.
- To investigate the role of specific effectors in the host-pathogen interaction.
Main Methods:
- Genome assembly of A. psidii strain MF-1 to identify 255 virulence effector candidates.
- Analysis of effector gene expression modulated by Eucalyptus leaf cell wax.
- Transient expression of effector candidates in Nicotiana benthamiana using GFP-fusions.
Main Results:
- Seven effector candidate genes showed modulated expression in response to leaf cell wax from resistant and susceptible Eucalyptus hosts.
- The nuclear effector candidate Ap28303, a peptidase inhibitor I9 domain-containing protein, was upregulated by cell wax from susceptible Eucalyptus.
- In silico analyses supported the predicted nuclear localization of Ap28303.
Conclusions:
- This study provides a valuable resource of A. psidii effector candidates for understanding myrtle rust pathogenesis.
- The identification of the nuclear effector Ap28303 offers a potential target for investigating host manipulation strategies in the A. psidii-Eucalyptus interaction.
