Dominance of Mating Type A1 and Indication of Epigenetic Effects During Early Stages of Mating in Phytophthora infestans

Abstract

The potato late blight pathogen Phytophthora infestans has both an asexual and a sexual mode of reproduction. In Scandinavia, the pathogen is reproducing sexually on a regular basis, whereas clonal lineages dominate in other geographical regions. This study aimed at elucidating events or key genes underlying this difference in sexual behavior. First, the transcriptomes of eight strains, known as either clonal or sexual, were compared during early stages of mating. Principal component analysis (PCA) divided the samples in two clusters A and B and a clear grouping of the mating samples together with the A1 mating type parents was observed. Induction of genes encoding DNA adenine N6-methylation (6mA) methyl-transferases clearly showed a bias toward the cluster A. In contrast, the Avrblb2 effector gene family was highly induced in most of the mating samples and was associated with cluster B in the PCA, similarly to genes coding for acetyl-transferases, which play an important role in RXLR modification prior to secretion. Avrblb2 knock-down strains displayed a reduction in virulence and oospore formation, suggesting a role during the mating process. In conclusion, a number of gene candidates important for the reproductive processes were revealed. The results suggest a possible epigenetic influence and involvement of specific RXLR effectors in mating-related processes.

Epigenetic insight into regulatory role of chromatin covalent modifications in lifecycle and virulence of Phytophthora

“…During mating of 10 different European P. infestans strain combinations, gene ontology analysis of transcriptome datasets showed significant enrichment of transferase activity, including the induced expression of eight acetyltransferases in strains and mating samples (Tzelepis et al, 2020). Since the authors only refer to these proteins as enzymes with putative acetyltransferase activity (Tzelepis et al, 2020), we looked for more specific HATs conserved domains and found that six of the reported proteins carry putative HATs domains. Both mating types of P. infestans (A1 and A2) are spread throughout Europe, increasing mating and leading to high genetic variability and more difficulties in controlling this pathogen (Heremans and Haesaert, 2004;Brurberg et al, 2011;Li et al, 2012;Runno-Paurson et al, 2016).…”

“…Furthermore, the epigenetic regulation of P. infestans sexual reproduction was recently proposed (Tzelepis et al, 2020). During mating of 10 different European P. infestans strain combinations, gene ontology analysis of transcriptome datasets showed significant enrichment of transferase activity, including the induced expression of eight acetyltransferases in strains and mating samples (Tzelepis et al, 2020).…”

“…Furthermore, the epigenetic regulation of P. infestans sexual reproduction was recently proposed (Tzelepis et al, 2020). During mating of 10 different European P. infestans strain combinations, gene ontology analysis of transcriptome datasets showed significant enrichment of transferase activity, including the induced expression of eight acetyltransferases in strains and mating samples (Tzelepis et al, 2020). Since the authors only refer to these proteins as enzymes with putative acetyltransferase activity (Tzelepis et al, 2020), we looked for more specific HATs conserved domains and found that six of the reported proteins carry putative HATs domains.…”

“…Another large family of histone demethylases comprises proteins with the Jumonji C (JmjC) domain capable to demethylate both Lys and Arg methylated residues (Tsukada et al, 2006;Chang et al, 2007). Recently, differential expression of a gene containing multiple Tudor domains (HDM-associated domains involved in chromatin binding) was reported during mating of P. infestans isolates from different European latitudes (Tzelepis et al, 2020), suggesting that HDMs are important in sexual reproduction (Fig. 1).…”

“…In another report, three DAMT genes showed differential expression patterns during mating between certain European parental strains of P . infestans (Tzelepis et al ., 2020). All three genes were upregulated during sexual reproduction suggesting a potential impact of DNA methylation on this process (Fig.…”