Sebastian Triesch (Heinrich Heine University Düsseldorf)
GUS staining of an Arabidopsis thaliana leaf. In two genetically modified A. thaliana lines, the GUS reporter gene was expressed under the control of two regulatory elements (promoters). The C3 variant of the promoter causes GUS-mediated blue coloration of the entire leaf. The regulatory region from the C3-C4 intermediate shows a structural genetic variation and mediates GUS staining only along the leaf veins. Image. Sebastian Triesch
Sebastian Triesch's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Heinrich Heine University Düsseldorf in the year 2021
Titl: Evolution of differential gene expression patterns in Brassicaceae with C3-C4 photosynthesis
C3-C4 intermediate plants provide an insight into the evolution of the highly complex C4 photosynthesis. In this work, genetic mechanisms underlying C3-C4 intermediate photosynthesis were investigated.
Photosynthesis, the central pathway for energy production in plants, suffers from the affinity of the enzyme Rubisco to atmospheric oxygen. When Rubisco reacts with oxygen, toxic by-products are formed. Therefore, over 60 times independently in evolution, the so-called C4 photosynthesis, a more efficient form of plant metabolism, arose. C4 photosynthesis is highly complex and occurs in only a few important crop plants. Plants that are “on the evolutionarily path” to C4 photosynthesis can help to better understand its evolution and find the genetic mechanisms that underlie it. These C3-C4 intermediate plants include, for example, Diplotaxis tenuifolia, also known as rocket.
To investigate the genetic underpinnings of C3-C4 intermediate photosynthesis, the genomes of over 20 species from the crucifer family (Brassicaceae) were used. Specifically, genetic traits that correlate with the occurrence of the C3-C4 intermediate phenotype were sought.
An important strategy in the evolution of C3-C4 intermediate photosynthesis is the cell-specific activity of certain genes. In this work, it was shown that a gene that plays an important role in photosynthesis is active in C3-C4 plants only along the leaf veins (see figure). In C3 plants, however, the gene is active throughout the leaf. At the genetic level, it was shown that a mobile DNA element (transposon) is selectively present in the regulatory region (promoter) of the gene only in C3-C4 plants. Interestingly, in three different species with C3-C4 intermediate photosynthesis, different types of structural variation can be found. Thus, in the evolution of C3-C4 photosynthesis, the same genetic mechanisms were probably found independently to shift the activity of the target gene specifically along the leaf veins.
The results of this work not only show how evolution finds similar genetic solutions to existing problems; they also point to possible starting points for genetic modification of plants. Highly complex phenotypes such as C4 photosynthesis can be introduced into crop plants once the basic genetic mechanisms that led to the natural evolution of the traits are understood.
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Sebastian Triesch conducted this work the Institute of Plant Biochemistry (Cluster of Excellence on Plant Sciences, CEPLAS) led by Prof. Dr. Andreas P. M. Weber.