FOREIGN MITOCHONDRIAL GENES IN A PARASITIC PLANT

PONCE, GABRIELA; SANCHEZ-PUERTA, M. VIRGINIA; GARCIA, LAURA E.; ROULET, MARIA EMILIA; GANDINI, CAROLINA L.

Mendoza

Congreso; XXXVI Reunión Científica Anual Sociedad de Biología de Cuyo; 2018

Sociedad de Biología de Cuyo

Parasitism is a highly successful life strategy originated independently in 11-13 lineages during the evolution of flowering plants.Parasitic plants are characterized by their ability to feed directly from other plants, invading the roots or stems of their plant hoststhrough a specialized structure called haustorium. This vascular connection allows the passage of water, nutrients, pathogens andnucleic acids. Consequently, parasitic relationships facilitate the exchange of genetic information, a process known as horizontalgene transfer (HGT). HGT refers to the movement of genetic information between unrelated organisms, and most cases of plantHGT involve the mitochondria, in contrast to nuclear and chloroplast compartments. Mitochondrial sequences of the donor aretransferred to the mitochondrial genome of another angiosperm and incorporated through homologous recombination. Parasitic plantsare particularly susceptible to this phenomenon and represent an excellent system to examine the role of HGT in the evolution of themitochondrial genome. In this study, we sequenced and analyzed the mitochondrial genome (mtDNA) of the holoparasiteOmbrophytum subterraneum (family Balanophoraceae). Total DNA extraction and massive sequencing with Illumina technologywere performed. The assembly of the DNA sequences was carried out with Velvet Assembler and Consed v29 based on informationof paired-end reads from the Illumina dataset. The mtDNA is composed of 56 circular molecules (1-27kb in length) totaling 713,111bp. This multipartite chromosomal architecture was recently described in a close relative, Lophophytum mirabile. The mtDNA wasannotated in Geneious using BLAST. The O. subterraneum mtDNA encodes 2 ribosomal RNA, 14 transfer RNA, and 30 proteingenes. The majority of these genes were present in multiple copies, resulting in a total of 65 genes. Only 29 chromosomes containcomplete mitochondrial genes, while the remaining are devoid of known genes. Maximum Likelihood phylogenetic analyses wereperformed for 24 protein genes to assess their evolutionary history. About 37.5% of them were associated with species of the FamilyAsteraceae, indicating that they were transferred from asterid hosts. Most foreign genes coexist with native homologs in themitochondrial genome of O. subterraneum. Additional studies are required to understand which copy is functional in O.subterraneum. Comparative analyses of the mitochondrial genomes of O. subterraneum and L. mirabile suggest that eachholoparasite acquired foreign sequences from their hosts in independent events.