GSO4SCHOOL Summer School 2020
Conifers make up one of the most successful groups of plants on Earth. Pines, spruces, and other coniferous species have dominated many forest ecosystems for millions of years. For instance, Earth’s oldest living individual plants belong to this group: the bristlecone pines in California; conifers are similarly Earth’s largest individual trees: the “giant Sequoias”. With around 650 different species, adaptation to different environments all over the Northern Hemisphere seems to flourish within this group.
This could not have escaped scientists’ interest and curiosity: What is the secret that makes conifers so successful? What is written in the evolutionary history of conifer species? What does their genetic code tell us about evolutionary success? How many functioning genes are in conifers’ genomes and how different is that from other plants or animals? Where exactly within the genome are those genes located, that might account for conifers’ longevity? Which are the genes that control important adaptive or economical traits and how are different phenotypes associated to different genotypes?
The first step has been taken: Norway spruce (the common Christmas tree with the scientific name Picea abies) was the first conifer to be sequenced, about two years ago, by scientists in Umeå Plant Science Center and the Science for Life Laboratory (SciLifeLab) in Stockholm. Its draft genome sequence is expected to shed plenty of light on some of these scientific questions or to provide educated guidelines for further basic or applied research in the fields of evolutionary biology and breeding.
However this is far from being a trivial task; Norway spruce’s genome counts ca. 20 Gb (gigabases pairs), and this is seven times larger than our own genome (3,2 Gb) and more than 100 times larger than the genome of the model plant species Arabidopsis thaliana, (0.135 Gb)! The mere size of Norway spruce’s genome makes sequencing even more challenging. Imagine trying to put in the correct order the letters, words and sentences of a text that was written in a language of four letters (the DNA nucleotides A, C, G, T) and had the length of 20 billion letters. And now imagine that almost half of this text consisted of repetitive sentences!
The genome sequence of Norway spruce resulted in the identification of ca. 28000 genes. Surprisingly, this number is very close to the ca. 27000 genes of A. thaliana, and slightly higher than the gene number of humans, despite its enormously larger genome.
Dr. Amaryllis Vidalis’ research at the group of Evolutionary Genetics, Department of Ecology and Environmental Sciences of Umea University (Sweden) focuses on the development of genetic probes that target practically all the expressed genes of Norway spruce, with a sequencing method called exome capture. The exome of an organism consists of all the “EXpressed regioONs” of its genes, or in other words, the “functional” part of its genome.
The ultimate goal of their research is the calculation of a genetic map (linkage map), that will not only make it possible to assign the majority of the genes of Norway Spruce to chromosomes for the first time, but will also facilitate the improvement of its genome assembly, by specifying the relative position of the genes, The genetic map of Norway spruce will be a very useful tool for association mapping of the genes of the species with specific adaptive and ecological traits, as well as economical characteristics such as growth, wood chemistry, wood physical properties (density, elasticity, structure etc.), reproduction properties and resistance to fungal infection.
The era of genomics, is vigorously invading the field of ecology. The possibilities of sequencing and genotyping full genomes at a low cost and in high speed, together with the accessibility to publicly available genomic resources, gives a unique advantage to the scientists that investigate non-model species in the field of ecological adaptation. The paradigm example of Norway spruce is just the beginning in the long and exciting way of untying the knot of conifer evolution, and its comparison with angiosperms and other lineages of life.
More info: http://congenie.org
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