Various types of mycorrhizal fungi sequences detected in single intracellular vesicles.

A diverse range of microbes have been observed to coexist in plant roots in the field, among which arbuscular mycorrhizal fungi (AMFs) are universal and have recently been shown to be of two types: one belonging to the subphylum Glomeromycotina (G-AMF) and the other to the subphylum Mucoromycotina (M-AMF). These two types of mycorrhizal fungi are known to co-occur in roots. This is because, in addition to the morphological evidence, diverse ribosomal RNA (rRNA) gene sequences, including those of G-AMF, are detected in mycorrhizae colonized with M-AMF. However, it is difficult to physically distinguish between these AMFs, and amplification bias of G-AMF and M-AMF by PCR has hampered analysis of the detailed symbiotic behaviour of both AMFs. In this study, we isolated a single vesicle of lipid-accumulating AMF in the root and sequenced its rRNA gene by PCR using uniquely designed primers with reduced amplification bias. Notably, G-AMF and M-AMF rRNA gene sequences were detected in one vesicle. These results suggest new avenues for mycorrhizal research on the overlooked morphology of AMF vesicles and their mode of genetic co-occurrence of G-AMF and M-AMF.