Transcriptomic profile of Plasmodiophora brassicae during the early stages of infection with a focus on overexpressed transcripts

Abstract: Plasmodiophora brassicae, a member of the eukaryotic supergroup Rhizaria, is a
unicellular obligate biotrophic endoparasite that targets brassica plant hosts. It causes clubroot disease which is characterized by the emergence of large galls on the roots of its host plants, which in turn leads to critical depletion in the crop yield. So far data on the physiological basis of the development of P. brassicae during the initial infection and colonization of its host are largely unknown. Here we present a first analysis of a RNAseq dataset at 7 days post inoculation (dpi) of clubroot infected Arabidopsis thaliana plants. By analyzing a select group of genes that exhibited differential expression at 7 dpi, we were able to infer their functional annotation, particularly for the ones that showed strong upregulation compared to later life cycle stages. Overall, we could identify transcripts that were specifically linked to acquiring nutrients, promoting growth, and facilitating development. Additionally, transcripts that have the potential to impact the host’s immune and stress response could be identified. Despite efforts, a considerable portion of genes remains unannotated, creating significant knowledge gaps in our understanding of the early infection. The functions closely match the expected processes in the initial infection phase, considering disease progression and the pathogen’s life cycle. Nontheless, recognizing active transcripts during infection is a notable milestone in pathogen and host interaction research.