Unveiling the Microbes of the World’s Largest Flower

The plant family Rafflesiaceae is known for producing the largest flowers in the world. They are solely parasitic to the plant genus Tetrastigma of the grape family. Interestingly, members of Rafflesiaceae are the only plants we know so far that have lost their chloroplast genome. Rafflesiaceae is comprised of three genera: Rafflesia, Sapria, and Rhizanthes. Members of Rafflesiaceae are restricted to the fast-disappearing tropical forests of Southeast Asia and are endangered. It is virtually unknown how Rafflesiaceae infects its hosts. This makes Rafflesiaceae very difficult to conserve and propagate. However, bacterial endophytes have shown to play a major role in promoting the growth of plants. In this study, we characterized and analyzed the associated microbiome of Rafflesiaceae, particularly Rafflesia speciosa and Sapria himalayana to find “microbial markers” of Rafflesiaceae infection. It was hypothesized that Rafflesia and its Tetrastigma host will have similar microbiomes given their intimate connection, however, results across different taxonomic levels demonstrate that Rafflesia buds have a distinct microbial endophyte composition and possessed some unique genera compared to its infected hosts. Its microbiome was also diverse compared to Sapria’s. Non-host Tetrastigma spp. possessed unique bacteria that may be antagonistic to Rafflesia infection. This study unveiled the symbiotic microbes of Rafflesia and Sapria, which may have potential horticultural application in propagating the world’s largest flowers.