Multichromosomal structure and foreign tracts in the Ombrophytum subterraneum (Balanophoraceae) mitochondrial genome

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

PLANT MOLECULAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2020

0167-4412

Horizontal gene transfer (HGT) is frequent in parasitic plant mitochondria as a result of vascular connections established inhost-parasite relationships. Recent studies of the holoparasitic plant Lophophytum mirabile (Balanophoraceae) revealed theunprecedented acquisition of a large amount of mitochondrial sequences from its legume host. We focused on a close rela-tive, the generalist holoparasite Ombrophytum subterraneum, to examine the incidence of HGT events in the mitochondrialgenome (mtDNA). The mtDNA of O. subterraneum assembles into 54 circular chromosomes, only 34 of which contain the51 full-length coding regions. Numerous foreign tracts (totaling almost 100 kb, ~ 14% of the mtDNA), including 12 intactgenes, were acquired by HGT from the Asteraceae hosts. Nine chromosomes concentrate most of those regions and eightare almost entirely foreign. Native homologs of each foreign gene coexist in the mtDNA and are potentially functional. Alarge proportion of shorter regions were related to the Fabaceae (a total of ~ 110 kb, 15.4%), some of which were sharedwith L. mirabile. We also found evidence of foreign sequences donated by angiosperm lineages not reported as hosts (Apoc-ynaceae, Euphorbiaceae, Lamiaceae, and Malvales). We propose an evolutionary hypothesis that involves ancient transfersfrom legume hosts in the common ancestor of Ombrophytum and Lophophytum followed by more recent transfer events inL. mirabile. Besides, the O. subterraneum mtDNA was also subjected to additional HGT events from diverse angiospermlineages, including large and recent transfers from the Asteraceae, and also from Lamiaceae.