Project description:Protein-coding genes are considered to be a dominant component of the eukaryotic transcriptome; however, many studies have shown that intergenic, non-coding transcripts also play an important role. Long intergenic non-coding RNAs (lincRNAs) were found to play a vital role in human and Arabidopsis. However, lincRNAs and their regulatory roles remain poorly characterized in woody plants, especially Populus trichocarpa (P. trichocarpa). A large set of Populus RNA-Seq data were examined with high sequencing depth under control and drought conditions and a total of 2542 lincRNA candidates were identified. In total, 51 lincRNAs and 20 lincRNAs were identified as putative targets and target mimics of known Populus miRNAs, respectively. A total of 504 lincRNAs were found to be drought responsive, eight of which were confirmed by RT-qPCR. These findings provide a comprehensive view of Populus lincRNAs, which will enable in-depth functional analysis.
Project description:BACKGROUND: Alternative splicing (AS) of genes is an efficient means of generating variation in protein structure and function. AS variation has been observed between tissues, cell types, and different treatments in non-woody plants such as Arabidopsis thaliana (Arabidopsis) and rice. However, little is known about AS patterns in wood-forming tissues and how much AS variation exists within plant populations. RESULTS: Here we used high-throughput RNA sequencing to analyze the Populus trichocarpa (P. trichocarpa) xylem transcriptome in 20 individuals from different populations across much of its range in western North America. Deep transcriptome sequencing and mapping of reads to the P. trichocarpa reference genome identified a suite of xylem-expressed genes common to all accessions. Our analysis suggests that at least 36% of the xylem-expressed genes in P. trichocarpa are alternatively spliced. Extensive AS was observed in cell-wall biosynthesis related genes such as glycosyl transferases and C2H2 transcription factors. 27902 AS events were documented and most of these events were not conserved across individuals. Differences in isoform-specific read densities indicated that 7% and 13% of AS events showed significant differences between individuals within geographically separated southern and northern populations, a level that is in general agreement with AS variation in human populations. CONCLUSIONS: This genome-wide analysis of alternative splicing reveals high levels of AS in P. trichocarpa and extensive inter-individual AS variation. We provide the most comprehensive analysis of AS in P. trichocarpa to date, which will serve as a valuable resource for the plant community to study transcriptome complexity and AS regulation during wood formation.
Project description:Populus trichocarpa is an important woody model organism whose entire genome has been sequenced. This resource has facilitated the annotation of microRNAs (miRNAs), which are short non-coding RNAs with critical regulatory functions. However, despite their developmental importance, P. trichocarpa miRNAs have yet to be annotated from numerous important tissues. Here we significantly expand the breadth of tissue sampling and sequencing depth for miRNA annotation in P. trichocarpa using high-throughput smallRNA (sRNA) sequencing. miRNA annotation was performed using three individual next-generation sRNA sequencing runs from separate leaves, xylem, and mechanically treated xylem, as well as a fourth run using a pooled sample containing vegetative apices, male flowers, female flowers, female apical buds, and male apical and lateral buds. A total of 276 miRNAs were identified from these datasets, including 155 previously unannotated miRNAs, most of which are P. trichocarpa specific. Importantly, we identified several xylem-enriched miRNAs predicted to target genes known to be important in secondary growth, including the critical reaction wood enzyme xyloglucan endo-transglycosylase/hydrolase and vascular-related transcription factors. This study provides a thorough genome-wide annotation of miRNAs in P. trichocarpa through deep sRNA sequencing from diverse tissue sets. Our data significantly expands the P. trichocarpa miRNA repertoire, which will facilitate a broad range of research in this major model system.
Project description:Our analysis provides a comprehensive picture of how P. trichocarpa responds to drought stress at physiological and transcriptome levels which may help to understand molecular mechanisms associated with drought response and could be useful for genetic engineering of woody plants. Drought stress treatment was performed dividing P. trichocarpa plants into the well-watered (WW) group (soil volumetric water content of 40â??45 %) and the water-limited group (soil volumetric water content of 10â??15 %). Two cDNA libraries constructed separately from the WW and WL groups were subjected to high-throughput Illumina sequencing.
Project description:A microarray analysis of whole-genome gene expression in leaves was carried out in a (Populus trichocarpa X Populus deltoides) X Populus deltoides pseudo-backcross pedigree. Genetic variation in gene expression was quantified for 55,793 predicted gene models based on a single probe per gene. Resultant data contributed to the analysis of the genetic architecture of gene expression in leaves of Populus. Overall design: Data include one biological replicate of 183 individuals segregating from a pseudo-backcross pedigree of (Populus trichocarpa X Populus deltoides) X Populus deltoides analyzed for gene expression (GE) in roots using one probe per gene for 55793 independent gene models (probes E_POPLARSxxxxxPxxxxx) and single feature sequence polymorphism (SFP) using one probe per gene for 12084 independent gene models (probes G_POPLARSxxxxxPxxxxx). GE and SFP probes were selected from 6-7 probes per gene previously tested in a pilot study of the two parent trees of the cross (Populus deltoides X Populus trichocarpa)
Project description:Illumina HiSeq2000 technology was used to generate mRNA profiles from the ectomycorrhizal fungi Laccaria bicolor colonizing roots of Populus trichocarpa. Samples were taken after 3 months of contact in order to identify mycorrhiza-regulated transcripts. 100bp reads were generated and aligned to the Populus trichocarpa (http://www.phytozome.net/poplar.php) reference genome. Overall design: mRNA profiles from Populus trichocarpa roots colonized by Laccaria bicolor for three months as well as from control roots were generated by using one lane of 1X100bp Illumina HiSeq2000 sequencing per sample.
Project description:The ages and sizes of a sex-determination region (SDR) are difficult to determine in non-model species. Due to the lack of recombination and enrichment of repetitive elements in SDRs, the quality of assembly with short sequencing reads is universally low. Unique features present in the SDRs help provide clues about how SDRs are established and how they evolve in the absence of recombination. Several Populus species have been reported with a male heterogametic configuration of sex (XX/XY system) mapped on chromosome 19, but the exact location of the SDR has been inconsistent among species, and thus far, none of these SDRs has been fully assembled in a genomic context. Here we identify the Y-SDR from a Y-linked contig directly from a long-read PacBio assembly of a Populus trichocarpa male individual. We also identified homologous gene sequences in the SDR of P. trichocarpa and the SDR of the W chromosome in Salix purpurea. We show that inverted repeats (IRs) found in the Y-SDR and the W-SDR are lineage-specific. We hypothesize that, although the two IRs are derived from the same orthologous gene within each species, they likely have independent evolutionary histories. Furthermore, the truncated inverted repeats in P. trichocarpa may code for small RNAs that target the homologous gene for RNA-directed DNA methylation. These findings support the hypothesis that diverse sex-determining systems may be achieved through similar evolutionary pathways, thereby providing a possible mechanism to explain the lability of sex-determination systems in plants in general.
Project description:A microarray analysis of whole-genome gene expression in roots was carried out in a (Populus trichocarpa X Populus deltoides) X Populus deltoides pseudo-backcross pedigree. Genetic variation in gene expression was quantified for 55,793 predicted gene models based on a single probe per gene. Resultant data contributed to the analysis of the genetic architecture of gene expression in roots of Populus. Overall design: Data include one biological replicate of 163 individuals segregating from a pseudo-backcross pedigree of (Populus trichocarpa X Populus deltoides) X Populus deltoides analyzed for gene expression (GE) in roots using one probe per gene for 55793 independent gene models (probes E_POPLARSxxxxxPxxxxx) and single feature sequence polymorphism (SFP) using one probe per gene for 12084 independent gene models (probes G_POPLARSxxxxxPxxxxx). GE and SFP probes were selected from 6-7 probes per gene previously tested in a pilot study of the two parent trees of the cross (Populus deltoides X Populus trichocarpa)