New papers from the Schön and Schwechheimer labs.
Stable Carbon Isotope Discrimination Is under Genetic Control in the C4 Species Maize with Several Genomic Regions Influencing Trait Expression.
Sebastian Gresset, Peter Westermeier, Svenja Rademacher, Milena Ouzunova, Thomas Presterl, Peter Westhoff and Chris-Carolin Schön (2014).
In plants with C4 photosynthesis, physiological mechanisms underlying variation in stable carbon isotope discrimination (Delta13C) are largely unknown, and genetic components influencing Delta13C have not been described. We analyzed a maize (Zea mays) introgression library derived from two elite parents to investigate whether Delta13C is under genetic control in this C4 species. High-density genotyping with the Illumina MaizeSNP50 Bead Chip was used for a detailed structural characterization of 89 introgression lines. Phenotypic analyses were conducted in the field and in the greenhouse for kernel Delta13C as well as plant developmental and photosynthesis-related traits. Highly heritable significant genetic variation for Delta13C was detected under field and greenhouse conditions. For several introgression library lines, Delta13C values consistently differed from the recurrent parent within and across the two phenotyping platforms. Delta13C was significantly associated with 22 out of 164 analyzed genomic regions, indicating a complex genetic architecture of Delta13C. The five genomic regions with the largest effects were located on chromosomes 1, 2, 6, 7, and 9 and explained 55% of the phenotypic variation for Delta13C. Plant development stage had no effect on Delta13C expression, as phenotypic as well as genotypic correlations between Delta13C, flowering time, and plant height were not significant. To our knowledge, this is the first study demonstrating Delta13C to be under polygenic control in the C4 species maize.
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ML3 is a NEDD8- and ubiquitin-modified protein.
Jana P. Hakenjos, Sarosh Bejai, Quirin Ranftl, Carina Behringer, Anna Corina Vlot, Birgit Absmanner , Ulrich Hammes, Stephanie Heinzlmeir, Bernhard Kuster, Claus Schwechheimer (2013).
NEDD8 (NEURAL PRECURSOR CELL-EXPRESSED, DEVELOPMENTALLY DOWN-REGULATED PROTEIN8) is an evolutionarily conserved 8-kD protein that is closely related to ubiquitin and that can be conjugated like ubiquitin to specific lysine residues of target proteins in eukaryotes. In contrast to ubiquitin, for which a broad range of substrate proteins are known, only a very limited number of NEDD8 target proteins have been identified to date. Best understood, and also evolutionarily conserved, is the NEDD8 modification (neddylation) of cullins, core subunits of the cullin-RING-type E3 ubiquitin ligases that promote the polyubiquitylation of degradation targets in eukaryotes. Here, we show that Myeloid differentiation factor-2-related lipid-recognition domain protein ML3 is an NEDD8- as well as ubiquitin-modified protein in Arabidopsis (Arabidopsis thaliana) and examine the functional role of ML3 in the plant cell. Our analysis indicates that ML3 resides in the vacuole as well as in endoplasmic reticulum (ER) bodies. ER bodies are Brassicales-specific ER-derived organelles and, similar to other ER body proteins, ML3 orthologs can only be identified in this order of flowering plants. ML3 gene expression is promoted by wounding as well as by the phytohormone jasmonic acid and repressed by ethylene, signals that are known to induce and repress ER body formation, respectively. Furthermore, ML3 protein abundance is dependent on NAI1, a master regulator of ER body formation in Arabidopsis. The regulation of ML3 expression and the localization of ML3 in ER bodies and the vacuole is in agreement with a demonstrated importance of ML3 in the defense to herbivore attack. Here, we extend the spectrum of ML3 biological functions by demonstrating a role in the response to microbial pathogens.
