The worldwide endoparasite family Apodanthaceae (Cucurbitales): Its natural history, biogeography, taxonomy, and plastid genome

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In flowering plants, parasitism has arisen some 11 times, four of them leading to endoparasitism in which parasites only emerge from the host to flower and fruit. Parasites´ most striking adaptations are the loss of leaves and photosynthetic capacity, and their communication with the host, including the exchange of proteins and nucleic acids. Perhaps not surprisingly, most cases of horizontal gene transfers in Viridiplantae come from parasitic plants. Genomic studies have focused on the exoparasites Cuscuta and Orobanchaceae, while only one endoparasite has been investigated (Rafflesia cantleyi, Xi et al., 2012). The present proposal focuses on the endoparasitic Apodanthaceae (Cucurbitales), a worldwide group of 18 species with minute (5 mm-long) flowers that mostly parasitize Fabaceae and on whose natural history we have accumulated data from fieldwork in Australia, Zimbabwe, and Iran. Partly analyzed Illumina/Solexa- and 454-sequenced plastomes of one Australian and one African species suggest more gene loss than found in any parasitic plant yet analyzed. We now plan to (i) produce a dated phylogeny for the Apodanthaceae using a novel approach, (ii) study the differentiation of their plastid genome compared to other parasites and autotrophic relatives (mainly Cucumis sativus), and (iii) look for horizontally transferred hosts genes. We also have on loan c. 450 specimens from 11 herbaria and will analyze species circumscriptions, geographic ranges, and host specificity.