The gene space of European mistletoe (Viscum album)

Abstract

European mistletoe (Viscum album) is a hemiparasitic flowering plant that is known for its very special life cycle and extraordinary biochemical properties. Particularly, V. album has an unusual mode of cellular respiration that takes place in the absence of mitochondrial complex I. However, insights into the molecular biology of V. album so far are very limited. Since the genome of V. album is extremely large (estimated 600 times larger than the genome of the model plant Arabidopsis thaliana) it has not been sequenced up to now. We here report sequencing of the V. album gene space (defined as the space including and surrounding genic regions, encompassing coding as well as 5 0 and 3 0 non-coding regions). mRNA fractions were isolated from different V. album organs 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 32 064 V. album proteins (designated V. album protein space). Our data give new insights into the metabolism and molecular biology of V. album, including the biosynthesis of lectins and viscotoxins. The benefits of the V. album gene space information are demonstrated by re-evaluating mass spectrometry-based data of the V. album mitochondrial proteome, which previously had been evaluated using the A. thaliana genome 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. The V. album gene space sequences are available at the NCBI.

Structural insights into the assembly and the function of the plant oxidative phosphorylation system

“…Nevertheless, no CA activity has been measured in vitro (Fromm et al ., 2016). Interestingly, the NDUCAs that form CI's CA domain are found in the mitochondrial proteome of European mistletoe (Petersen et al ., 2022; Schroder et al ., 2022), which does not have CI (Maclean et al ., 2018; Senkler et al ., 2018). This suggests that NDUCAs may have additional functions unrelated to CI.…”

The photosynthesis apparatus of European mistletoe (Viscum album)

“…We used 44 gel slices for the thylakoid fractions from V. album and A. thaliana , respectively ( Supplemental Figure S4 ). Data from MS were evaluated using the Araport11 database ( https://www.arabidopsis.org/ ) for A. thaliana and the V. album gene space database ( https://viscumalbum.pflanzenproteomik.de/ , Schröder et al, 2022a ) for V. album . Table 1 summarizes our results: For both species, about 400–600 proteins were detected per gel fraction ( Figure 4 ; Supplemental Figure S5 ).…”

“…BN gel lanes were each horizontally dissected into 44 gel slices, and subjected to label-free quantitative shotgun proteomics ( Supplemental Figure 4 ). Top: Identified proteins per gel slice fraction in V. album ; evaluation of MS data was based on the V. album gene space database; https://viscumalbum.pflanzenproteomik.de/ , Schröder et al (2022a) . Bottom: Identified proteins per gel slice fraction in A. thaliana ; evaluation of MS data was based on the Araport11 database ( https://www.arabidopsis.org/ ).…”

“…Initially, it was reported that several genes are absent in the mitochondrial genomes of Viscum species, which code for subunits of the NADH dehydrogenase complex (Complex I) of the respiratory chain ( Petersen et al, 2015a ; Skippington et al, 2015 ; Skippington et al, 2017 ). It was later shown that the entire enzyme complex, which is composed of close to 50 protein subunits in plants ( Klusch et al, 2021 ), is absent in V. album ( MacLean et al, 2018 ; Senkler et al, 2018 ; Petersen et al, 2022 ; Schröder et al, 2022a ). Currently, mistletoe species are the only examples of multicellular organisms that can carry out cellular respiration in the absence of Complex I ( Petersen et al, 2020 ).…”

The future of Viscum album L. in Europe will be shaped by temperature and host availability

“…Recently, mistletoe has become a plant of relatively high interest, and a large number of papers have been published on this species covering morphology, chemistry, genetics, and occurrence 25 , 32 , 35 , 36 , 38 – 42 . To date, however, no work has been published on modelling the potential future European range of this species, which would allow us to better understand the currently observed dynamics of mistletoe spread and to plan strategies related to the management of forests threatened by this hemi-parasite 28 , 43 .…”