The gene space of European mistletoe (Viscum album)

SUMMARYEuropean mistletoe (Viscum album) is a hemiparasitic flowering plant that is known for its very special life cycle and extraordinary biochemical properties. Particularly,V. albumhas an unusual mode of cellular respiration that takes place in the absence of mitochondrial complex I. However, insights into the molecular biology ofV. albumso far are very limited. Since the genome ofV. albumis extremely large (estimated 600 times larger than the genome of the model plantArabidopsis thaliana) it has not been sequenced up to now. We here report sequencing of theV. albumgene space (defined as the space including and surrounding genic regions, encompassing coding as well as 5′ and 3′ non‐coding regions). mRNA fractions were isolated from differentV. albumorgans harvested in summer or winter and were analyzed via single‐molecule real‐time sequencing. We determined sequences of 39 092 distinct open reading frames encoding 32 064V.albumproteins (designatedV. albumprotein space). Our data give new insights into the metabolism and molecular biology ofV. album, including the biosynthesis of lectins and viscotoxins. The benefits of theV. albumgene space information are demonstrated by re‐evaluating mass spectrometry‐based data of theV. albummitochondrial proteome, which previously had been evaluated using theA. thalianagenome sequence. Our re‐examination allowed the additional identification of nearly 200 mitochondrial proteins, including four proteins related to complex I, which all have a secondary function not related to respiratory electron transport. TheV. albumgene space sequences are available at the NCBI.