Are fungi‐derived genomic regions related to antagonism towards fungi in mosses?
Résumé
Land plants have been intimately associated with fungi over the course of their evolution. Because of their lack of sophisticated protective structures, early land plants would conceivably have required additional defense strategies against microbial pathogens, including various fungi. On the other hand, a symbiotic association between plants and fungi is instrumental to plant adaptation to terrestrial environments (Selosse & Le Tacon, 1998; Bidartondo et al., 2011; Martin et al., 2017). The crucial role of this partnership is further evidenced by the widespread occurrence of mycorrhiza (root–fungi association) in vascular plants, as well as mycorrhiza-like fungal associations (MFAs hereafter) in nonvascular plants, such as liverworts and hornworts (Wang & Qiu, 2006; Pressel et al., 2014). Surprisingly, although fungal symbiosis is commonly considered to be an ancestral trait for land plants (Wang & Qiu, 2006; Delaux et al., 2015), with the possible exception of the genus Takakia (Boullard, 1988; Grosche et al., 2018), no MFAs have been confirmed in other mosses (Pressel et al., 2014; Field et al., 2015), the most diverse group of nonvascular land plants.
Here, we report two genomic regions in the nuclear genome of the moss Physcomitrium patens, previously Physcomitrella patens (Medina et al., 2019; Rensing et al., 2020), that contain mostly fungi-specific genes and mobile genetic elements. These two regions were identified in our genome screening for horizontally acquired genes in P. patens. Available evidence indicates that these fungi-specific genes are probably involved in the interaction between mosses and fungi. We discuss how these fungi-specific genes might have contributed to the defense against fungal and other microbial pathogens, as well as the loss of MFAs in mosses.