Bacteria helped plants to colonize the land
Scientists found that around 580 million years ago, soil bacteria transferred their genes into early ancestors of algae and vascular land plants. The phenomenon, called horizontal gene transfer, probably helped plants to cope with droughts. It involved at least two gene families: GRAS and PYR/PYL/RCAR.
The insights were gathered thanks to genome sequencing of S. musicola and M. endlicherianium at ~400X coverage. The first organism was found to posses over 27 thousand genes, in comparison to the second, which harbors 11 thousand genes. This difference was attributed to the recent triplication of the whole genome.
Genomic comparisons with bacteria and land plants revealed 902 common genes, including at least two gene groups contributing to dessication-related conditions.
We suggest that the common ancestor of Zygnematophyceae and embryophytes already lived in a subaerial/terrestrial environment and obtained genes from soil bacteria that, after diversification, played an important role in the evolution and radiation of embryophytes, regulating processes from growth and development to defense against biotic and abiotic stresses and to symbiotic interactions.
Graphical abstract provided by Cell:
Publication: Cheng, S., Xian, W., Fu, Y., Marin, B., Keller, J., Wu, T., … Melkonian, M. (2019). Genomes of Subaerial Zygnematophyceae Provide Insights into Land Plant Evolution. Cell, 179(5), 1057–1067.e14. doi:10.1016/j.cell.2019.10.019.
Photo: Tina Carvalho, University of Hawaii at Manoa.