Researchers in Brno have discovered an unexpected trend in plant genomes through their research. Based on prior studies, they anticipated that the genome size, which significantly affects plant growth, would increase from the equator towards the poles. However, their research showed significant differences between the Northern and Southern Hemispheres, attributed to how genome size influences plant distribution in relation to the local climate.
The unique investigation began in 2016, involving collaboration with British colleagues from the Royal Botanic Gardens, Kew. The study eventually included more than 16,000 species of angiosperms, or flowering plants, the most species-rich plant lineage that has adapted to a wide range of environments across all continents. According to the Brno botanists, the tremendous diversity in their genome sizes could open new perspectives on their evolution and biogeography.
"Our research on the global distribution of genome sizes showed that while in the Southern Hemisphere, plant genome size increases from the equator towards the pole, in the Northern Hemisphere, it increases only towards the temperate climate zone and then decreases further north. The largest genome sizes are then found between the 40th and 50th parallels," summarized Prof. Petr Bureš from the Department of Botany and Zoology at the Faculty of Science, Masaryk University. "This belt includes, for example, areas from Southern Europe to the Czech Republic or the territory between New York and Canada in North America," added team member František Zedek from the Faculty of Science, MU, for better visualization.
A global map of genome sizes, a result of the study recently published in the prestigious journal New Phytologist by the team led by Petr Bureš, suggests that the different trends in genome sizes between the Northern and Southern Hemispheres might be due to the Northern Hemisphere's inhabitable land extending far beyond the Arctic Circle. Here, plants have to cope with much lower temperatures than on the continents of the Southern Hemisphere inhabited by plants. These lower temperatures in the north slow down cell division, which, combined with a large genome, would be unsustainable. Another important finding of the Czech-British study is that plants with a broader geographical distribution (occupying large geographic ranges) do not have large genomes.
The size of a genome, or the weight of DNA in a cell nucleus, can be determined both by sequencing (reading the sequence of nucleotides) the entire genome and more easily and quickly by measuring the fluorescence of cell nuclei using a flow cytometer. The research on the global distribution of plant genome sizes was supported by the Czech Science Foundation under project GA20-15989S and primarily took place in the cytometry laboratory of the Institute of Botany and Zoology, equipped with eight flow cytometers, a "fleet" unmatched by any other cytometry facility in plant biology worldwide.
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