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.
Highlights
Phytophthora infestans is one of the most devastating plant pathogens, infecting many species in the Solanaceae family, potato and tomato
The overall aim of the current work was to advance the understanding of mechanisms explaining differences of mating capacity at the early stages between different European P. infestans strains
Based on single nucleotide polymorphism (SNPs) data, we found that the Sw1 genotype was more similar to the Dutch and British strains than to the three other Swedish strains
Summary
Phytophthora infestans is one of the most devastating plant pathogens, infecting many species in the Solanaceae family, potato and tomato. It is a fungal-like, filamentous pathogen, which belongs to Oomycota. Its leading role as one of the most notorious plant pathogens worldwide is associated with its rapid adaptation to fungicides and newly introduced plant resistance genes (Fry, 2008) This high speed of adaptation can be explained by an efficient and mixed reproduction system, and the large amount of effector genes and transposable elements in the P. infestans genome (Fry, 2008; Haas et al, 2009). Mating in P. infestans requires the presence of A1 and A2 mating types, leading to zygote formation within the developing oospore (Goodwin and Drenth, 1997)
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