Label-Free Quantitative Proteomic Analysis of <i>Puccinia psidii</i> Uredospores Reveals Differences of Fungal Populations Infecting Eucalyptus and Guava

<div><p><i>Puccinia psidii</i> sensu lato (s.l.) is the causal agent of eucalyptus and guava rust, but it also attacks a wide range of plant species from the myrtle family, resulting in a significant genetic and physiological variability among populations accessed from different hosts. The uredospores are crucial to <i>P</i>. <i>psidii</i> dissemination in the field. Although they are important for the fungal pathogenesis, their molecular characterization has been poorly studied. In this work, we report the first in-depth proteomic analysis of <i>P</i>. <i>psidii</i> s.l. uredospores from two contrasting populations: guava fruits (PpGuava) and eucalyptus leaves (PpEucalyptus). NanoUPLC-MS^E was used to generate peptide spectra that were matched to the UniProt <i>Puccinia</i> genera sequences (UniProt database) resulting in the first proteomic analysis of the phytopathogenic fungus <i>P</i>. <i>psidii</i>. Three hundred and fourty proteins were detected and quantified using Label free proteomics. A significant number of unique proteins were found for each sample, others were significantly more or less abundant, according to the fungal populations. In PpGuava population, many proteins correlated with fungal virulence, such as malate dehydrogenase, proteossomes subunits, enolases and others were increased. On the other hand, PpEucalyptus proteins involved in biogenesis, protein folding and translocation were increased, supporting the physiological variability of the fungal populations according to their protein reservoirs and specific host interaction strategies.</p></div

Gene ontology of biological process terms in the proteomic analysis.

<p>Bar graph represents the ratio of % composition of term in the proteomic data.</p

Proteins identified from <i>P</i>. <i>psidii</i> uredospore populations.

<p>The proteins exclusively found in PpGuava (right) and PpEucalyptus (left) and common to both populations (center). Of the common proteins, 25 and 120 whose abundance were increased in PpEucalyptus and PpGuava, respectively.</p

Morphological and viability analysis of <i>Puccinia psidii</i> uredospores.

<p><i>P</i>. <i>psidii</i> uredospores from <i>E</i>. <i>grandis</i><b>(A)</b> and <i>P</i>. <i>guajava</i><b>(B)</b> exhibit similar morphology and germination viability, respectively <b>(C and D)</b>.The arrows indicate the fungal germ tube in both uredospore populations, 24 hours after inoculation in water-agar medium. Light microscopy images of PpEucalyptus and PpGuava uredospores are shown at 100 X (A and B) and 200 X (C and D) magnification. Scale bar: 20 μm in A and B, 50 μm in C and D.</p

Eucalyptus infection by guava and eucalyptus rust.

<p>Symptoms induced by inoculation of <i>P</i>. <i>psidii</i> uredospores from PpEucalyptus <b>(A)</b> on <i>E</i>. <i>grandis</i> variety D901. This clone is rust susceptible when grown under field conditions. The white arrows indicate the fungal pustules. The leaves are shown 15 days after inoculation.The PpGuava populations <b>(B)</b> and control <b>(C)</b> did not show typical rust symptoms.</p

Protein profiles in PpGuava and PpEucalyptus and the correlation with their physiological variability.

<p>While proteins correlated to fungal virulence and stress response had the abundance increased in PpGuava, proteins related to biogenesis, protein folding and translation had the abundance increased in PpEucalyptus.</p