Cytonuclear coevolution in a holoparasitic plant with highly disparate organellar genomes

CERIOTTI, LUIS FEDERICO; GATICA SORIA, LEONARDO MARTIN; SÁNCHEZ PUERTA, MARÍA VIRGINIA

;

Congreso; I Congreso Latinoamericano de Evolución-CLEVOL, 2021; 2021

Sociedad Chilena de Evolución SOCEVOL; Asociación Colombiana de Biología Evolutiva COLEVOL; Sociedad Argentina de Biología Evolutiva SABE

The organellar genomes of the holoparasitic plant Lophophytum (Balanophoraceae) are exceptional. In the non-photosynthetic plastid, the genome has been severely reduced and presents a >85% AT content. In contrast, most protein-coding genes in the mitochondrial genome have been replaced by homologs acquired by horizontal gene transfer (HGT) from their hosts (Fabaceae). Genes in both genomes encode proteins that form multi-subunit complexes with products of nuclear genes, creating the opportunity for cytonuclear coevolution. In this study, we assessed the evolutionary rates, and their impact on cyto-nuclear evolution, of genes involved in multi-subunit complexes related to lipid biosynthesis and proteolysis in the plastid and those in charge of the oxidative phosphorylation in the mitochondria. A subset of non-organellar nuclear genes was included as a measure of the substitution rate in the nuclear genome. Genes in the plastid and the mitochondrial (both native and foreign) genomes of Lophophytum showed extremely high and ordinary substitution rates, respectively. Consistent with this, nuclear genes encoding subunits of plastid complexes showed disproportionate increases in non-synonymous substitution rates, while those of the mitochondrial complexes did not show different rates than the control (i.e. non-organellar nuclear genes). Moreover, the rate increases in the nuclear-encoded subunits of plastid complexes were positively correlated with the level of physical interaction they exhibit with the plastid-encoded ones. Overall, these results suggest that a structurally-mediated compensatory factor may be driving plastid-nuclear coevolution and that mito-nuclear coevolution was not obviously altered by HGT.