Gene loss and horizontal gene transfer in plants as a consequence of parasitism
Authors
Karsten Fischer (presenting author) [1]
Stian Olsen [1]
Rainer Schwanke [2]
Kirsten Krause [1]
Keywords
Cuscuta; genomics; horizontal gene transfer; NUP genes; parasitic plants
Abstract
The parasitic flowering plant genus Cuscuta (dodder) is a parasitic weed that infects many important crops. Once it winds around the shoots of potential host plants and initiates the development of penetration organs, called haustoria, only a few plant species have been shown to deploy effective defense mechanisms to ward off Cuscuta parasitization. In contrast to photosynthetically active non-parasitic plants, Cuscuta has only limited need for photosynthesis and an ensuing reduced or absent capacity for autotrophic growth, leading to a different selection pressure on the parasite’s genomes. While the chloroplast genome has been intensively studied in the past, the analysis of the other cellular genomes has lagged significantly behind. With the publication of the first parasitic plant genomes in 2018 (Cuscuta campestris by Vogel et al. and C. australis by Sun et al.), it has finally become possible to investigate what effect the morphological and physiological reductions have had on their overall gene content and coding capacity. An emerging hallmark of Cuscuta’s genomes are losses of genes performing redundant or obsolete functions. On the other hand, new genes were gained by trans-species horizontal gene transfer from the genomes of their numerous host plants. Based on an analysis of an extensive dataset including the parasite Cuscuta campestris and other parasitic plant species, we identified unique evolutionary histories of some of their genes that will be exemplified here with the gene rpl32 which codes for an essential plastid ribosomal subunit in angiosperm plants.
Funding
Tromsø Research Foundation, Grant #16-TF-KK to Krause.