Alternative splicing regulation in plants by effectors of symbiotic arbuscular mycorrhizal fungi

Most plants in natural ecosystems live in association with AM (arbuscular mycorrhizal) fungi to survive under poor nutrient conditions and to cope with other abiotic and biotic stresses. To engage in symbiosis, AM fungi secrete effector molecules that, similar to pathogenic effectors, reprogram plant cells. Despite numerous effectors being predicted in the genome of AM fungi, only a few have been functionally characterized. Here we show that the SP7-like family, a Glomeromycotina-specific effector family, impacts on the alternative splicing program of their hosts. SP7-like effectors localize at nuclear condensates and interact with the plant mRNA processing machinery, most prominently with the splicing factor SR45 and the core splicing proteins U170K and U2AF35. Ectopic expression of two of these effectors in the crop plant potato changed the alternative splicing pattern of a specific subset of genes. Unravelling the communication mechanisms between symbiotic fungi and their host plants will help to identify targets to improve plant nutrition.