Living with a giant, flowering parasite: metabolic differences between Tetrastigma loheri Gagnep. (Vitaceae) shoots uninfected and infected with Rafflesia (Rafflesiaceae) and potential applications for propagation

Jeanmaire Molina,William Mclaughlin,Ronniel Pedales,Elmer-Rico E Mojica,James Adams,Jashvanth Raaj Jeevarathanam,Ari Novy,Dejan Nikolic,Eun-Jung Park,Danilo Tandang,Richard B Van Breemen,Rinat Abzalimov,Kyle Wallick,John M Pezzuto,Susan K Pell

doi:10.1007/s00425-021-03787-x

Abstract

Main conclusionMetabolites in Rafflesia-infected and non-infected Tetrastigma were compared which may have applications in Rafflesia propagation. Benzylisoquinoline alkaloids, here reported for the first time in Vitaceae, were abundant in non-infected shoots and may be a form of defense. In Rafflesia-infected shoots, oxylipins, which mediate immune response, were elevated.Endemic to the forests of Southeast Asia, Rafflesia (Rafflesiaceae) is a genus of holoparasitic plants producing the largest flowers in the world, yet completely dependent on its host, the tropical grape vine, Tetrastigma. Rafflesia species are threatened with extinction, making them an iconic symbol of plant conservation. Thus far, propagation has proved challenging, greatly decreasing efficacy of conservation efforts. This study compared the metabolites in the shoots of Rafflesia-infected and non-infected Tetrastigma loheri to examine how Rafflesia infection affects host metabolomics and elucidate the Rafflesia infection process. Results from LC–MS-based untargeted metabolomics analysis showed benzylisoquinoline alkaloids were naturally more abundant in non-infected shoots and are here reported for the first time in the genus Tetrastigma, and in the grape family, Vitaceae. These metabolites have been implicated in plant defense mechanisms and may prevent a Rafflesia infection. In Rafflesia-infected shoots, oxygenated fatty acids, or oxylipins, and a flavonoid, previously shown involved in plant immune response, were significantly elevated. This study provides a preliminary assessment of metabolites that differ between Rafflesia-infected and non-infected Tetrastigma hosts and may have applications in Rafflesia propagation to meet conservation goals.

Highlights

Rafflesia (Rafflesiaceae, Malpighiales) is a genus of plants producing the world’s largest flowers (Fig. 1), yet it is a holoparasite with no stems, roots or leaves, deriving all nutrients solely from its host vine, the genus Tetrastigma (Vitaceae; Nais 2001; Davis et al 2007)
One uninfected cutting was found to be T. papillosum (Blume) Planch., and liquid chromatography–mass spectrometry (LC–MS) raw data for this sample were excluded from further analysis to rule out interspecific differences in metabolites
We sought to determine which metabolites were significantly different between Rafflesia-infected and non-infected T. loheri to understand how Rafflesia infection affects host metabolomics, to characterize these unique metabolites, as well as assess their potential ecological roles to generate insights that can facilitate a Rafflesia infection to aid in conservation efforts

Summary

Introduction

Rafflesia (Rafflesiaceae, Malpighiales) is a genus of plants producing the world’s largest flowers (Fig. 1), yet it is a holoparasite with no stems, roots or leaves, deriving all nutrients solely from its host vine, the genus Tetrastigma (Vitaceae; Nais 2001; Davis et al 2007). 30 species that are unique to the tropics of Southeast Asia with many endangered of extinction (Barcelona et al 2009; Wicaksono et al 2016). Efforts to propagate Philippine Rafflesia for ex situ conservation have had only incremental success (Molina et al 2017). Molina and collaborators have been transporting Rafflesia-infected Tetrastigma cuttings from the Philippines for propagation at the United States Botanic Garden (USBG) in Washington, D.C. since 2015. The cuttings have rooted and survived for a maximum of 11 months, but no shoots have been produced

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