Horizontal gene transfer (HGT) is the transfer of genetic material across species boundaries and has been a driving force in prokaryotic evolution. HGT involving eukaryotes appears to be much less frequent, and the functional implications of HGT in eukaryotes are poorly understood. We test the hypothesis that parasitic plants, because of their intimate feeding contacts with host plant tissues, are especially prone to horizontal gene acquisition. We sought evidence of HGTs in transcriptomes of three parasitic members of Orobanchaceae, a plant family containing species spanning the full spectrum of parasitic capabilities, plus the free-living Lindenbergia. Following initial phylogenetic detection and an extensive validation procedure, 52 highconfidence horizontal transfer events were detected, often from lineages of known host plants and with an increasing number of HGT events in species with the greatest parasitic dependence. Analyses of intron sequences in putative donor and recipient lineages provide evidence for integration of genomic fragments far more often than retro-processed RNA sequences. Purifying selection predominates in functionally transferred sequences, with a small fraction of adaptively evolving sites. HGT-acquired genes are preferentially expressed in the haustorium-the organ of parasitic plants-and are strongly biased in predicted gene functions, suggesting that expression products of horizontally acquired genes are contributing to the unique adaptive feeding structure of parasitic plants.

Habitat fragmentation is a major concern of conservation biologists, since reduced gene flow between isolated subpopulations may further decrease the effective population size of a species. Rock wallaby (genus Petrogale) colonies provide a naturally occurring system to study the genetic consequences of habitat fragmentation. Colonies of less than 10 to more than 50 adult rock wallabies are restricted to isolated rock outcrops, and are thus expected to exhibit the genetic and demographic consequences of small population size. In this paper, we describe the characterization of a series of microsatellite loci from the allied rock-wallaby, Petrogale assirnilis, and their use to estimate genetic variation. Despite the small population sizes, a high degree of heterozygosity was observed at all the loci investiga ted.Single-locus microsatellite typing exploits the natural variability of simple repetitive sequences, and has been extensively employed in the medical sciences and in animal husbandry. Despite the potential applications of this technology in conservation genetics, few marsupial microsatellite loci have been characterized to date. In a wide range of eutherian mammals, microsatellites with the general form (TG), are by far the most common class in the genome (see, for example, Moore et nl. 1991). Our preliminary studies (Odorico et aI. 1992) imply that this is also true for marsupials. We therefore characterized a series of (TG), microsatellite loci from I? ussimilis, with the aim of developing microsatellite PCR systems for kinship and population studies.A partial genomic library was constructed for P. ussimilis and screened by standard techniques (Weber L May 1989;Tautz 1989; reviewed in Queller et nl. 1993). In the initial round of screening, seven clones containing (TG), microsatellites with n > 20 were identified; several additional clones contained imperfect or lower numbers of (TG), repeats. A further single clone contained ( n X o and another a complex locus containing two tetranucleotide repeats (Table 1). Oligonucleotide primers were designed to enable PCR amplification at several of these loci (Table 1); in one case the repeat region was too close to the end of the clone to permit this, and in a second case the microsatellite was monomorphic. For two other (TG), loci we do not yet have allelic data.PCR reactions were performed in 1 0 -m~ Tris containing 5 0 -m~ KC1, 1.5-m~ MgCl, 1 unit of Taq polymerase (Promega) and 50-100 ng of template DNA in a total volume of 25 ycL. For each locus, the dNTP (0.2-0.8 mM) and primer (1-8 IIM) concentrations were optimized, and in each case one of the primers was end-labelled using [y-XPI-ATP. Varying the primer and dNTP concentrations were found to have major effects on the amount of 'bandstuttering' (Tautz 1989; Luty et al. 1990) observed, and hence the interpretability of results. After an initial denaturation period of 5 min at 95 "C, 30 cycles of PCR were performed, each cycle consisting of 1 min denaturation at 93 "C, 30 s at the annealing temperature (Tab...

Background Parasitic plants engage in a complex molecular dialog with potential host plants to identify a host and overcome host defenses to initiate development of the parasitic feeding organ, the haustorium, invade host tissues, and withdraw water and nutrients. While one of two critical signaling events in the parasitic plant life cycle (germination via stimulant chemicals) has been relatively well-studied, the signaling event that triggers haustorium formation remains elusive. Elucidation of this poorly understood molecular dialogue will shed light on plant-plant communication, parasitic plant physiology, and the evolution of parasitism in plants. Results Here we present an experimental framework that develops easily quantifiable contrasts for the facultative generalist parasitic plant, Triphysaria , as it feeds across a broad range of diverse flowering plants. The contrasts, including variable parasite growth form and mortality when grown with different hosts, suggest a dynamic and host-dependent molecular dialogue between the parasite and host. Finally, by comparing transcriptome datasets from attached versus unattached parasites we gain insight into some of the physiological processes that are altered during parasitic behavior including shifts in photosynthesis-related and stress response genes. Conclusions This work sheds light on Triphysaria’s parasitic life habit and is an important step towards understanding the mechanisms of haustorium initiation factor perception, a unique form of plant-plant communication. Electronic supplementary material The online version of this article (10.1186/s12870-019-1856-1) contains supplementary material, which is available to authorized users.