AUTHOR=D’Andrea Lucio , Sierro Nicolas , Ouadi Sonia , Hasing Tomas , Rinaldi Elijah , Ivanov Nikolai V. , Bombarely Aureliano 

TITLE=Polyploid Nicotiana section Suaveolentes originated by hybridization of two ancestral Nicotiana clades

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 14 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.999887

DOI=10.3389/fpls.2023.999887

ISSN=1664-462X

ABSTRACT=Nicotiana section Suaveolentes is an almost all-Australian clade of allopolyploid tobacco species that emerged through hybridization between diploid relatives of the genus. In this study, we aimed to assess the phylogenetic relationship of the Suaveolentes section with several Nicotiana diploid species based on both plastidial and nuclear-encoded genes. The Nicotiana plastome-based phylogenetic analysis representing 47 newly re-built plastid genomes suggested that an ancestor of the N. section Noctiflorae is the most likely maternal donor of the Suaveolentes clade. Nevertheless, we found clear evidence of plastid recombination with an ancestor from the Sylvestres clade. We analyzed 411 maximum likelihood-based phylogenetic trees from a set of conserved nuclear-encoded diploid single copy gene families following an approach that assessed the genomic origin of each homeolog. We found that Nicotiana section Suaveolentes is monophyletic with contributions from the sections Alatae, Sylvestres, Petunioides and Noctiflorae. The dating of the divergence between these sections indicates that the Suaveolentes hybridization event predates the split between Alatae/Sylvestres, and Noctiflorae/Petunioides.  We propose that Nicotiana section Suaveolentes arose from the hybridization of two ancestral species from which the Noctiflorae/Petunioides and Alatae/Sylvestris sections are derived, with Noctiflorae the maternal parent. This study is a good example in which the use of genome wide data provided additional evidence about the origin of a complex polyploid clade.