Biology subjects

Sipilä, T.

Publications and source records attributed to Sipilä, T..

3 recordsLinked to original sources

bioRxiv2021

A Taphrina strain infecting the model plant Arabidopsis thaliana.

Yeasts are important plant-associated organisms that can modulate host immunity to either promote or prevent disease. Mechanisms of plant-yeast interactions, specifically of yeast perception by the plant innate immune system, remain unknown. Progress has been hindered by the scarcity of yeast species associated with the model plant Arabidopsis thaliana (Arabidopsis). We have previously isolated Taphrina strain M11 from wild Arabidopsis in the field. Taphrina are poorly studied dimorphic yeast-like fungi that are plant pathogens, often producing plant hormones and causing tumour-like and leaf deformation symptoms on their hosts. Here we characterize the interaction of M11 with Arabidopsis. Infection of Arabidopsis with the birch pathogen T. betulina, used as a non-host control, shows early HR, enhanced ROS accumulation, and limitation of growth, demonstrating that Arabidopsis had immunity against non-adapted yeasts. M11 triggered limited cell death, an attenuated ROS response, and grew in planta, as well as subtle but clear leaf deformation symptoms, demonstrating it is pathogenic. Hormone responsive promoter-reporter analysis demonstrated activation of cytokinin signalling during infection. Mutant infection assays indicate jasmonate and ethylene were required for immunity against M11. Analysis of the Taphrina M11 genome was used to mine evidence for yeast specific PAMPs which may underlie host immune responses against yeast-like fungi.

plant biology↗

bioRxiv2019

A novel Arabidopsis phyllosphere resident Protomyces sp. and a re-examination of genus Protomyces based on genome sequence data.

Protomyces is a genus of yeast-like fungi that is currently defined as plant pathogens of only the Umbelliferae (Apiaceae) and Compositae (Asteraceae) family plants. Many Protomyces species have been proposed; however, there is a lack of molecular data and available specimens for Protomyces spp., just over ten species are officially accepted and only six species are preserved and available in public culture collections for examination. Phylogenetic relationships and species boundaries within this genus remain largely controversial. Recently, we isolated Protomyces strains from wild Arabidopsis thaliana (Arabidopsis), a Brassicaceae family plant only distantly related to the accepted Protomyces hosts. We have previously sequenced the genomes of all the currently public available Protomyces species, together with a strain (SC29) we isolated from the Arabidopsis phyllosphere. Genome-wide phylogenetic analysis suggests that SC29 occupies a unique phylogenetic position in the genus Protomyces. The SC29 genome has low average nucleotide identity values in comparison with other species genomes. As physiological evidence, SC29 has morphological characteristics and carbon assimilation patterns that distinguish it from the other six Protomyces species. Analysis with several nuclear gene phylogenetic markers further confirms SC29 as a novel Protomyces species and suggests the act1 gene DNA sequences can be used together with ITS sequences for the rapid identification of Protomyces species. In our previous study, SC29 could persist on the Arabidopsis phyllosphere in both short term laboratory and overwinter outdoor garden experiments and Protomyces spp. (or OTUs) were found in the Arabidopsis phyllosphere at multiple sites in both Finland and Germany. We conclude that SC29 is a novel Protomyces species isolated from Arabidopsis and propose the name of Protomyces arabidopsidicola sp. nov. Additionally, the genus Protomyces may not be strictly associated with only Compositae or Umbelliferae family host plants, as evidenced by SC29 and Protomyces strains previously isolated from plants in other families. The merging of two Protomyces species found to have high genomic similarity (P. inouyei and P. lactucaedebilis) is also proposed.

microbiology↗

bioRxiv2019

A novel phyllosphere resident Protomyces species that interacts with the Arabidopsis immune system.

We describe the genome contents of six Protomyces spp. that are pathogenic within the typical host range of the genus and a novel Protomyces strain (SC29) that was previously isolated from the phylloplane of wild Arabidopsis thaliana (Arabidopsis), an atypical or possible alternate host. Genome-wide phylogenetic analysis defined SC29 as a distinct Protomyces sp. Analysis of gene family expansions, gene retention, and gene loss patterns among these Protomyces spp. lead us to hypothesize that SC29 may have undergone a host jump. The role of phyllosphere residency in the lifecycle of Protomyces spp. was previously unknown. Genomic changes in SC29 and all other Protomyces spp. were consistent with adaptations to the plant phylloplane. As predicted by our analysis of its mating locus, SC29 did not cause disease on Arabidopsis as a single strain, but could persist in its phylloplane, while the closely related P. inouyei does not. SC29 treated Arabidopsis exhibited enhanced immunity against Botrytis cinerea infection, associated with activation of MAPK3/6, camalexin, and SA-signalling pathways. We conclude that SC29 is a novel Protomyces sp. able to survive in the Arabidopsis phylloplane and that phylloplane residency is an important element in the lifecycle of Protomyces spp.

microbiology↗