The oomycetes are a lineage of filamentous Eukaryotes most closely related to the heterokont (brown) algae. Many oomycetes are plant pathogens, however, some Pythium species are parasitic to fungi and other oomycetes (Pythium oligandrum and Pythium periplocum) whilst others such as Lagenidium giganteum are parasites of insects including mosquitos that vector Zika virus and Dengu fever. These three species have great potential as biocontrol agents. Molecular, genetic and genomic data from these species provides new insights into pathogenicity and the fundamental biology of oomycetes with diverse lifestyles beyond the well-studied plant pathogens.
We have carried out de novo genome sequencing and genome-wide transcriptomics (RNA-seq) of these three understudied oomycetes, using both paired end and mate pair Illumina Hiseq sequencing. In combination with lipidomic and cell wall proteomics data of the oospores, which are the major inoculum used in commercial preparations of P. oligandrum, our data will illuminate the genetic and molecular determinants of host specificity, reproduction and survival of these species.
RNA-seq data from P. oligandrum and P. periplocum colonising the potato late blight oomycete Phytophthora infestans reveals ABC transporters are important for mycoparasitism. Novel transcripts, including putative R-genes from P. infestans reveal how this oomycete defends itself against mycoparasitic attack, and may provide vital clues for the sustainable control of potato late blight in the future. Traits important for successful mycoparasitism are being revealed by comparative analyses of the hyper-aggressive mycoparasite P. oligandrum versus the weaker mycoparasite P. periplocum. We are also assessing the effects of these biocontrol agents on overall soil health. Microbiome sequencing reveals that P. oligandrum can affect changes within the soil bacterial community structure of potato roots when applied in the field. The implications of these data for the control of plant diseases and insect pests using oomycete biocontrol agents will be discussed.