The neighbouring genes AvrLm10A and AvrLm10B are part of a large multigene family of cooperating effector genes conserved in Dothideomycetes and Sordariomycetes

Abstract

Fungal effectors (small-secreted proteins) have long been considered as species or even subpopulation-specific. The increasing availability of high-quality fungal genomes and annotations has allowed the identification of trans-species or trans-genera families of effectors. Two avirulence effectors, AvrLm10A and AvrLm10B, of Leptosphaeria maculans, the fungus causing stem canker of oilseed rape, are members of such a large family of effectors. AvrLm10A and AvrLm10B are neighbouring genes, organized in divergent transcriptional orientation. Sequence searches within the L. maculans genome showed that AvrLm10A/AvrLm10B belong to a multigene family comprising five pairs of genes with a similar tail-to-tail organization. The two genes, in a pair, always had the same expression pattern and two expression profiles were distinguished, associated with the biotrophic colonization of cotyledons and/or petioles and stems.Of the two protein pairs further investigated, AvrLm10A_like1/AvrLm10B_like1 and AvrLm10A_like2/AvrLm10B_like2, the second one had the ability to physically interact, similarly to what was previously described for the AvrLm10A/AvrLm10B pair, and cross-interactions were also detected for two pairs. AvrLm10A homologues were identified in more than 30 Dothideomycete and Sordariomycete plant-pathogenic fungi. One of them, SIX5, is an effector from Fusarium oxysporum f. sp. lycopersici physically interacting with the avirulence effector Avr2. We found that AvrLm10A/ SIX5 homologues were associated with at least eight distinct putative effector families, suggesting that AvrLm10A/SIX5 is able to cooperate with different effectors.These results point to a general role of the AvrLm10A/SIX5 proteins as "cooperating proteins", able to interact with diverse families of effectors whose encoding gene is co-regulated with the neighbouring AvrLm10A homologue.

Breeding and management of major resistance genes to stem canker/blackleg in Brassica crops

“…Another example is the two-gene for one gene interaction between both AvrLm10A and AvrLm10B and Rlm10. These two avirulence genes are necessary to induce avirulence towards Rlm10 (Petit-Houdenot et al 2019;Talbi et al 2023). Some other avirulence genes have dual recognition specificities, such as AvrLm4, which was renamed AvrLm4-7 as it can generate a resistance response in the presence of both Rlm4 and Rlm7 (Parlange et al 2009), or AvrLm5-9 that induces responses to both Rlm5 and Rlm9 (Van De Wouw et al 2014;Ghanbarnia et al 2018;).…”