Regulation of Zn and Fe transporters by the GPC1 gene during wheat monocarpic senescence
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ABSTRACT: TaGPC1 and TaGPC2 are NAC-domain transcription factors which accelerate the onset of senescence and facilitate nutrient translocation in wheat. We developed knockout mutants of these genes in tetraploid wheat and used RNA-seq to identify the effect of these mutations on the wheat flag leaf transcriptome during monocarpic senescence. Several transporter-related genes were identified which were upregulated during senescence and differentially expressed between genotypes.
Project description:TaGPC1 and TaGPC2 are NAC-domain transcription factors which accelerate the onset of senescence and facilitate nutrient translocation in wheat. We developed knockout mutants of these genes in tetraploid wheat and used RNA-seq to identify the effect of these mutations on the wheat flag leaf transcriptome during monocarpic senescence. Several transporter-related genes were identified which were upregulated during senescence and differentially expressed between genotypes. Illumina cDNA libraries were constructed from four biological replicates of three genotypes (WT, gpc-a1 and gpc-a1/gpc-b2) at three timepoints (Heading date, 12 days after anthesis and 22 days after anthesis). Reads were aligned to a collection of assembled genomic contigs from flow-sorted chromosome arms (A and B genomes only) provided by the International Wheat Genome Sequencing Consortium. A custom GTF file was generated to identify 139828 gene loci corresponding to transcribed regions of this reference sequence. Please note that the contig names provided by URGI (http://wheat-urgi.versailles.inra.fr/Seq-Repository) were used in the analysis. Most, but not all, of these loci are present in Ensembl (With a modified name, but the same basic information, chromosome arm and unique contig ID) at ftp://ftp.ensemblgenomes.org/pub/plants/release-22/fasta/triticum_aestivum/dna/ Therefore, the contig IDs from URGI (which are available for all our sequences) were used in the processed data file (i.e. the count table and GFF file) and an additional file describing the corresponding Ensembl names for these was provided (Additional_file_2.xlsx).
Project description:Bread wheat (Triticum aestivum cv. Mace) mature and senescent flag leaves were collected over a 48 h time course in continuous conditions to investigate changes in circadian clock regulation that occur during leaf senescence.
Project description:To explore the effect of stable RNAi on the small RNA (sRNA) population in wheat, we constructed a sRNA library from hexaploid wheat that expresses an RNAi construct under the 35S promoter that targets the endogenous NO APICAL MERISTEM (TaNAM) gene. The presence of this RNAi transgene causes a 40% reduction in expression of the target genes as measured by quantitative RT-PCR and significantly delays senescence and reduces remobilization of N, Fe, and Zn to the grain. RNA was extracted from flag-leaves of transgenic NAM-RNAi plants at 12 days post-anthesis. RNA was collected from a pool of flag-leaves from four plants.
Project description:We used isobaric tags for relative and absolute quantitation (iTRAQ) to perform a quantitative proteomic analysis of immature spikes harvested from tetraploid near-isogenic lines of wheat with normal spikelete (NSs), FRSs, and RSs and investigated the molecular mechanisms of lateral meristem differentiation and development. This work provides valuable insight into the underlying functions of the lateral meristem and how it can produce differences in the branching of tetraploid wheat spikes.
Project description:Wheat is a cereal grain and one of the world’s major food crops. Recent advances in wheat genome sequencing are by now facilitating genomic and proteomic analyses of this crop. However, little is known about the protein levels of hexaploid versus tetraploid wheat cultivars, and knowledge on phosphorylated proteins still limited. Using our recently established (phospho)proteomic workflow, we performed a parallel analysis of the proteome and phosphoproteome on seedling leaves from two hexaploid wheat cultivars (Pavon 76 and USU-Apogee) and a tetraploid wheat (Senatore Cappelli). This revealed that a large portion of proteins and phosphosites can be quantified in all cultivars. Our shotgun proteomics data revealed a high similarity between hexaploid and tetraploid varieties with respect to protein abundance. However, we could identify a set of proteins that were differentially abundant between hexaploid and tetraploid cultivars. In addition, already at seedling stage, a small set of proteins were differential between the small (USU-Apogee) and larger hexaploid wheat cultivar (Pavon 76), which could potentially act as growth predictors. Finally, the phosphosites identified in this study can be retrieved from the in-house developed plant PTM-Viewer (bioinformatics.psb.ugent.be/webtools/ptm_viewer/), making this the first repository for phosphorylated wheat proteins. This paves the way for further in depth, quantitative (phospho)proteome-wide differential analyses upon a specific trigger or environmental change.
Project description:A transcriptomic time-course study was performed on the senescence process in flag leaves of the spring wheat cultivar Bobwhite grown in the green-house. Leaf samples were harvested at eight time-points from the time of ear emergence until 50% yellowing of the harvested leaf sample.
Project description:During wheat senescence, leaf components are degraded in a coordinated manner, releasing amino acids and micronutrients which are subsequently transported to the developing grain. We have previously shown that the simultaneous downregulation of Grain Protein Content (GPC) transcription factors, GPC1 and GPC2, greatly delays senescence and disrupts nutrient remobilization, and therefore provide a valuable entry point to identify genes involved in micronutrient transport to the wheat grain.We generated loss-of-function mutations for GPC1 and GPC2 in tetraploid wheat and showed in field trials that gpc1 mutants exhibit significant delays in senescence and reductions in grain Zn and Fe content, but that mutations in GPC2 had no significant effect on these traits. An RNA-seq study of these mutants at different time points showed a larger proportion of senescence-regulated genes among the GPC1 (64%) than among the GPC2 (37%) regulated genes. Combined, the two GPC genes regulate a subset (21.2%) of the senescence-regulated genes, 76.1% of which are upregulated at 12 days after anthesis, before the appearance of any visible signs of senescence. Taken together, these results demonstrate that GPC1 is a key regulator of nutrient remobilization which acts predominantly during the early stages of senescence. Genes upregulated at this stage include transporters from the ZIP and YSL gene families, which facilitate Zn and Fe export from the cytoplasm to the phloem, and genes involved in the biosynthesis of chelators that facilitate the phloem-based transport of these nutrients to the grains.This study provides an overview of the transport mechanisms activated in the wheat flag leaf during monocarpic senescence. It also identifies promising targets to improve nutrient remobilization to the wheat grain, which can help mitigate Zn and Fe deficiencies that afflict many regions of the developing world.
Project description:A global, systems-based study of the transcriptome response of three drought resistant durum wheat genotypes to water stress. Two parents of a mapping population (Lahn x Cham 1) and a recombinant inbred line (RIL2219), selected for their drought resistance in multiyear field trials, were subjected to controlled time series water stress and samples taken over a six day period to study flag leaf gene expression in parallel with physiological measurements. The aim was to dissect the responses to water stress in an attempt to identify molecular and physiological properties defining stress resistance and thus to build knowledge to accelerate the breeding effort.