Some parasitic plants steal genetic material from their host plants and use the stolen genes to more effectively siphon off the host's nutrients. A new study led by researchers at Penn State and Virginia Tech reveals that the parasitic plant dodder has stolen a large amount of genetic material from its hosts, including over 100 functional genes. These stolen genes contribute to dodder's ability to latch onto and steal nutrients from the host and even to send genetic weapons back into the host. The new study appears on July 22, 2019, in the journal Nature Plants. "Horizontal gene transfer, the movement of genetic material from one organism into the genome of another species, is very common in microbes and is a major way that bacteria can acquire antibiotic resistance," said Claude dePamphilis, professor of biology at Penn State and senior author of the study. "We don't see many examples of horizontal gene transfer in complex organisms like plants, and when we do see it, the transferred genetic material isn't generally used. In this study, we present the most dramatic case known of functional horizontal gene transfer ever found in complex organisms."
Parasitic plants like dodder cannot live on their own by generating energy through photosynthesis. Instead, they use structures called haustoria to tap into a host plant's supply of water and nutrients. Dodder wraps itself around its host plant, growing into its vascular tissue, and often feeds on multiple plants at one time. It can parasitize many different species, wild plants as well as those of agricultural and horticultural importance. "Parasitic plants live very intimately in connection with their host, extracting nutrients," said dePamphilis. "But they also get genetic material in the process, and sometimes they incorporate that material into their genome. Previous studies focused on single transferred genes. Here, we used genome-scale datasets about gene expression to determine whether the large amount of genetic material coming over through horizontal gene transfer is actually being used."
The research team identified 108 genes that have been added to dodder's genome by horizontal gene transfer and now seem to be functional in the parasite, contributing to haustoria structure, defense responses, and amino acid metabolism. One stolen gene even produces small segments of RNA known as micro RNAs that are sent back into the host plant, acting as weapons that may play a role in silencing host defense genes. The team used rigorous criteria to determine whether the stolen genetic material was likely to be functional: The genes had to be full length, they had to contain all the necessary parts of a gene, they had to be transcribed into an RNA sequence that later builds proteins, and they had to be expressed in relevant structures. The team also explored the evolution of these transferred genes as additional support for functionality.
(Source: Agriculture and Food News, Science Daily. www.sciencedaily.com)