Project description:Sustainable production of switchgrass (Panicum virgatum) as a bioenergy crop hinges in part on efficient use of soil macronutrients, especially nitrogen (N). This study investigated the physiological, metabolic and transcriptomic responses of switchgrass to N limitation. Moderate N limitation marked a tipping point for large changes in plant growth, root-to-shoot ratio, root system architecture and total nitrogen content. Integration of transcriptomic and metabolic data revealed that N limitation reduced switchgrass photosynthetic capacity and carbon(C)-fixation activities. Switchgrass balanced C-fixation with N-assimilation, transport and recycling of N compounds by rerouting C-flux from glycolysis, the oxidative branch of the pentose phosphate pathway (OPPP) and from the tricarboxylic acid (TCA) cycle in an organ specific manner. The energy and reduction power so generated, and C-skeletons appear to be directed towards N uptake, biosynthesis of energy storage compounds with high C/N ratio such as sucrose, non-N-containing lipids, and various branches of secondary metabolism.
Project description:Knowing how switchgrass (Panicum virgatum L.) responds and adapts to phosphorus (P)-limitation will aid efforts to optimize P acquisition and use in this species for sustainable biomass production. This integrative study investigated the impacts of mild, moderate, and severe P-stress on genome transcription and whole-plant metabolism, physiology and development in switchgrass. P-limitation reduced overall plant growth, increased root/shoot ratio, increased root branching at moderate P-stress, and decreased root diameter with increased density and length of root hairs at severe P-stress. RNA-seq analysis revealed thousands of genes that were differentially expressed under moderate and severe P-stress in roots and/or shoots compared to P-replete plants, with many stress-induced genes involved in transcriptional and other forms of regulation, primary and secondary metabolism, transport, and other processes involved in P-acquisition and homeostasis. Amongst the latter were multiple miRNA399 genes and putative targets of these. Metabolite profiling showed that levels of most sugars and sugar alcohols decreased with increasing P stress, while organic and amino acids increased under mild and moderate P-stress in shoots and roots, although this trend reversed under severe P-stress, especially in shoots.
Project description:In this project, we report on aluminum (Al)-induced root proteomic changes in switchgrass. After growth in a hydroponic culture system supplemented with 400μM of Al, plants began to show signs of physiological stress such as a reduction in photosynthetic rate. At this time, the basal 2‐cm long root tips were harvested and divided into two segments, each of 1‐cm in length, for protein extraction. Al-induced changes in proteomes were identified using tandem mass tags mass spectrometry (TMT-MS)-based quantitative proteomics analysis. A total of 216 proteins (approximately 3.6% of total proteins) showed significant differences between non-Al treated control and treated groups with significant fold change (twice the standard deviation; FDR adjusted p-value, q<0.05). The basal root tip tissues expressed more dramatic proteome changes (164 significantly changed proteins; 3.9% of total proteins quantified) compared to the elongation/maturation zones (52 significantly changed proteins, 1.1% of total proteins quantified). Significantly changed proteins from the basal-1cm root apex tissues were clustered into 25 biological pathways, three proteins in cell cycles were all at a reduced abundance level compared to the non-treated control group. In the root elongation and maturation zone tissues, the identified proteins were placed into 18 pathways, proteins in secondary cell wall formation (lignin biosynthesis) were identified. Several STRING protein interaction networks were developed for these Al-induced significantly changed proteins. This study has identified a large number of Al-responsive proteins, including transcription factors, which will be used for exploring new Al tolerance genes and mechanisms.
Project description:In this project, we report on aluminum (Al)-induced root proteomic changes in switchgrass. After growth in a hydroponic culture system supplemented with 400μM of Al, plants began to show signs of physiological stress such as a reduction in photosynthetic rate. At this time, the basal 2‐cm long root tips were harvested and divided into two segments, each of 1‐cm in length, for protein extraction. Al-induced changes in proteomes were identified using tandem mass tags mass spectrometry (TMT-MS)-based quantitative proteomics analysis. A total of 216 proteins (approximately 3.6% of total proteins) showed significant differences between non-Al treated control and treated groups with significant fold change (twice the standard deviation; FDR adjusted p-value, q<0.05). The basal root tip tissues expressed more dramatic proteome changes (164 significantly changed proteins; 3.9% of total proteins quantified) compared to the elongation/maturation zones (52 significantly changed proteins, 1.1% of total proteins quantified). Significantly changed proteins from the basal-1cm root apex tissues were clustered into 25 biological pathways, three proteins in cell cycles were all at a reduced abundance level compared to the non-treated control group. In the root elongation and maturation zone tissues, the identified proteins were placed into 18 pathways, proteins in secondary cell wall formation (lignin biosynthesis) were identified. Several STRING protein interaction networks were developed for these Al-induced significantly changed proteins. This study has identified a large number of Al-responsive proteins, including transcription factors, which will be used for exploring new Al tolerance genes and mechanisms.
Project description:Small RNA libraries were constructed, sequenced, and analyzed with our Sequence Homology Pipeline for miRNA discovery (Jeong et al. 2013) to identify 59 unique conserved miRNA sequences from 199 precursors in switchgrass.
Project description:We profiled the root and shoot transcriptomes of BFO-colonized (Bacteria, Fungi, Oomycetes) and germ free A. thaliana exposed to Low PAR (photoactive radiation, LP) and normal condition (NC) in the gnotobiotic FlowPot system five weeks post inoculation.