Molecular identification of mQTL and overlapping biomass QTL´s

Quantitative genetic approaches are followed to identify novel genes important for metabolic composition and/or plant growth advantage. These studies are performed in close collaboration with Prof. Dr. T Altmann, IPK Gatersleben in Arabidopsis thaliana and with Prof. Dr. Melchinger in Zea mays.

In case of A. thaliana, several RIL and NIL populations established for a number of Arabidopsis thaliana ecotypes which were developed in the group of Prof Altmann, carry the additional advantage that they display large variation in biomass and are derived from a F1 cross showing strong heterosis. Applying metabolic profiling towards these populations has allowed the identification of more than 200 QTL´s for more than 100 metabolites. A large fraction of these QTL´s were found in both RIL´s and corresponding NIL´s.

In addition, based on the simultaneous analysis of biomass and metabolite composition it was possible to predict biomass based on the metabolic profile. Both metabolites with known and unknown chemical structure contributed to the predictor. Metabolic profiling of test crosses between RIL´s and the corresponding parents has resulted in the identification of a number of heterotic metabolic QTL´s. Analysis of the chromosome segment carrying the mQTL for potential candidate genes and their subsequent analysis by reversed genetics T-DNA KO lines) has in several cases allowed the validation of the candidate gene as indeed being responsible for the metabolic QTL.

In case of Zea Mays, a population of about 300 inbred lines and two tester lines were grown in the field at two locations and leaf samples harvested about 4 weeks after germination were analyzed for their metabolic composition. Again candidate genes for several metabolites were identified. Furthermore some of these mQTL´s overlapped with QTL´s mapped in the same population encoding agronomic traits. Under the (nonvalidated) assumption that at least in some cases the mQTL and the agronomic trait QTL are indeed encoded by the same gene this would offer a new approach for identifying novel routes for improving given agronomic traits via modulating metabolic traits.

References

Lisec, J., Meyer, R.C., Steinfath, M., Redestig, H., Becher, M., Witucka-Wall, H., Fiehn, O., Torjek, O., Selbig, J., Altmann, T. & Willmitzer, L. Identification of metabolic and biomass QTL in Arabidopsis thaliana in a parallel analysis of RIL and IL populations. Plant Journal 53,960-972 (2008).

Brotman, Y., Riewe, D., Lisec, J., Meyer, R.C., Willmitzer, L. & Altmann, T. Identification of enzymatic and regulatory genes of plant metabolism through QTL analysis in Arabidopsis. Journal of Plant Physiology 168, 1387-1394 (2011).

Riewe, D., Mehrana, K., Lisec, J., Pfeiffer, M., Lippmann, R., Schmeichel, J., Willmitzer, L. & Altmann, T. A tyrosine aminotransferase involved in tocopherol synthesis in Arabidopsis . Plant Journal 71, 850-859 ( 2012)

Riedelsheimer, C., Lisec, J., Czedik-Eysenberg, A., Sulpice, R., Flis, A., Grieder, C., Altmann, T., Stitt, M., Willmitzer, L. & Melchinger, A.E. Genome-wide association mapping of leaf metabolic profiles for dissecting complex traits in maize. Proceedings of the National Academy of Sciences of the United States of America 109, 8872-8877 (2012).

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