bioRxiv | 2021
Conservation and diversity in transcriptional responses among host plants forming distinct arbuscular mycorrhizal morphotypes
Abstract
The morphotype of arbuscular mycorrhizal (AM) roots is distinct mostly depending on AM host species: Arum, Paris, and Intermediate types. We previously reported that gibberellin (GA) promotes the establishment of Paris-type AM symbiosis in Eustoma grandiflorum despite its negative effects on Arum-type AM symbiosis in model plants. However, the molecular mechanisms underlying the differential effects of GA on different morphotypes, including Intermediate-type AM symbiosis, remain elusive. Comparative transcriptomics revealed that several symbiosis-related genes were transcriptionally promoted upon AM fungal colonization in Lotus japonicus (Arum-type), Daucus carota (Intermediate-type), and E. grandiflorum (Paris-type). Interestingly, upon GA treatment, the fungal colonization levels and expression of symbiosis-related genes were suppressed in L. japonicus and D. carota but were promoted in E. grandiflorum. Exogenous GA transcriptionally inhibited the biosynthetic process of a host-derived signal molecule involved in AM symbiosis, strigolactone, in L. japonicus and E. grandiflorum. Additionally, disaccharides mainly metabolized in AM roots would be different between L. japonicus and D. carota/E. grandiflorum. This study uncovered the conserved transcriptional responses during mycorrhization and diverse responses to GA in AM roots with distinct morphotypes among phylogenetically distant host plants.