Atypical RXLR effectors are involved in pathogenesis.

Unlabelled: RXLR effectors are pathogenic factors secreted from oomycetes to manipulate the immunity of the host. Typical RXLR effectors contain an RXLR-dEER motif at the N-terminus, whereas atypical RXLRs show variations on this motif. The oomycete is known to infect over 200 plant species, resulting in significant agricultural economic losses. Although genome-wide identification and functional analyses of typical RXLRs from have been performed, little is known of atypical PcaRXLRs. Here, we identified RXLRs, both typical and atypical, in and compared them with those of other oomycete pathogens. Fewer RXLRs were identified in compared with other species, possibly due to fewer duplication events of RXLRs. In contrast, the percentage of atypical RXLRs was higher in than in other species, suggesting significant roles in pathogenesis. Analysis of RXLR gene expression showed that most were transcribed, suggesting their functionality. Transient expression of two atypical RXLRs in showed that they induced necrosis dependent on host SGT1 and HSP90. Furthermore, two additional atypical RXLRs suppressed the defense response in and promoted infection. These results demonstrate the vital role of atypical RXLRs in and provide valuable information on their evolutionary patterns and interactions with host plants.

Supplementary Information: The online version contains supplementary material available at 10.1007/s42994-025-00198-4.