Is it easy to become C2? - Molecular components and evolutionary significance of Gldp promoter regulation in Arabidopsis thaliana
Plant Genetics and Genomics
Final Report Abstract
During photosynthesis plants fix atmospheric CO2 into carbohydrates. The associated photosynthetic assimilation rates differ among different photosynthetic variants, in which C3 photosynthesis represents the more ancestral photosynthetic variant, whereas C4 photosynthesis evolved much later. C4 photosynthesis evolved independently more than 60 times, possibly via intermediate C3-C4 variants that are referred to as plant species with C2 photosynthesis and which are considered to be a bridge between C3 and C4 photosynthesis. A better understanding of the molecular basis of the evolution of C4 holds the potential of improving crop productivity. This project focused mainly on one of the earliest steps of development of the C4-trait which is assumed to be the restriction of the glycine decarboxylase (GDC) complex to the bundle sheath (BS) of C2 plants. By using promoter deletion mutants, this work shows that restriction of the GDC to the BS of C3 plants is possible. The cis-element responsible for this spatial expression was isolated from the promoter of AtGldp1, one of the two genes encoding the GDC-P subunit in A. thaliana. The identified element is referred to as the M-box. Bioinformatic analysis shows the presence of the M-box in promoters of several C3 Gldp1 Brassicaceae genes and its loss from promoters of several C2 Moricandia Gldp genes. This provides a potential molecular mechanism for restriction of GDC to BS, at least in the genus Moricandia. The bioinformatic analysis was further validated experimentally by isolating additional previously uncharacterized C3 and C2 promoters from other species of the genus Moricandia by restriction genome walking. It was shown that the M-box is present in the promoter of a C3 Moricandia species but absent in Gldp promoters of three different C2 Moricandia species. The isolated promoters were further studied in A. thaliana. Furthermore, a potential M-box binding factor was defined to be a member of the GATA transcription factor family via a yeast-one-hybrid screening coupled with co-expression analyses and the processing of previous genome-wide footprint sequencing data. Collective results from this study identify and characterize a simple mechanism for establishing C2-specific gene expression in a C3 plant like A. thaliana.
Publications
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(2015) A simple mechanism for the establishment of C2-specific gene expression in Brassicaceae. The Plant Journal 84: 1231–1238
Adwy W, Laxa M, Peterhänsel C
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(2019) Loss of the M-box from the glycine decarboxylase P-subunit promoter in C2 Moricandia species. Plant Gene
Adwy W, Schlüter U, Papenbrock J, Peterhänsel C, Offermann S
