1-06: Global changes in mineral transporters in the crowns and rhizomes of an upland tetraploid switchgrass over a growing season

Mineral uptake, mobilization, and recycling in perennial bioenergy feedstocks, such as switchgrass, are keys for sustainable production of biomass.  Understanding how these processes work and are controlled can lead to the identification of genetic markers which can be used to breed improved cultivars.  Utilizing bioinformatics and the switchgrass draft genome (Pvi0) released by the DOE-Joint Genomes Institute (JGI) we identified many of the putative mineral transporters encoded by the switchgrass genome. We identified approximately 40 classes of nutrient transporters comprised of 520 genes in the tetraploid switchgrass genome, compared to 274 and 281 nutrient transporter genes in the related diploid C4 grasses Sorghum bicolor and Setaria italica respectively.  We next analyzed the expression levels of these transporters in crowns and rhizomes, which comprise the junction point between the shoots and roots, and thereby play an important role in controlling mineral flux between the above ground and below ground tissues.  We used existing Roche Instruments 454 crown and rhizome transcriptome datasets gathered over the course of a growing season to obtain expression profiles for 401 of the 520 genes identified by bioinformatics.  qPCR of select genes was used to verify if the observed expression profiles matched the predicted profiles obtained from 454 sequencing.  Analysis of crown and rhizome expression data, coupled with mineral abundance measurements in the same tissue provided insights into the mineral assimilation and translocation patterns between the rhizosphere and tillers over the course of a growing season.  Data from several experiments addressing these issues will be discussed.