Sequence of the Mitochondrial Genome of Lactuca virosa Suggests an Unexpected Role in Lactuca sativa’s Evolution

• Published in: Frontiers in plant science Vol. 12
• Main Authors: Fertet, Arnaud, Graindorge, Stéfanie, Koechler, Sandrine, de Boer, Gert-Jan, Guilloteau-Fonteny, Emilie, Gualberto, José M.
• Format: Journal Article
• Language: English
• Published: Frontiers 26-07-2021; Frontiers Media S.A
• Subjects: genome evolution; Lactuca saligna; Lactuca serriola; Lactuca virosa; lettuce; Life Sciences; mitochondrial genome; Plant Science; Vegetal Biology
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2021.697136

The involvement of the different
Lactuca
species in the domestication and diversification of cultivated lettuce is not totally understood.
Lactuca serriola
is considered as the direct ancestor and the closest relative to
Lactuca sativa
, while the other wild species that can be crossed with
L. sativa
,
Lactuca virosa
, and
Lactuca saligna
, would have just contributed to the latter diversification of cultivated typologies. To contribute to the study of
Lactuca
evolution, we assembled the mtDNA genomes of nine
Lactuca
spp. accessions, among them three from
L. virosa
, whose mtDNA had not been studied so far. Our results unveiled little to no intraspecies variation among
Lactuca
species, with the exception of
L. serriola
where the accessions we sequenced diverge significantly from the mtDNA of a
L. serriola
accession already reported. Furthermore, we found a remarkable phylogenetic closeness between the mtDNA of
L. sativa
and the mtDNA of
L. virosa
, contrasting to the
L. serriola
origin of the nuclear and plastidial genomes. These results suggest that a cross between
L. virosa
and the ancestor of cultivated lettuce is at the origin of the actual mitochondrial genome of
L. sativa.