Project description:To better understand the molecular control of leaf senescence, we examined transcriptome changes during seasonal leaf senescence in Populus trichocarpa Nisqually-1, the Populus reference genome, growing in its natural habitat. Using monthly (from May to October) transcriptomes for three years (2009, 2015, and 2016), we identified 17,974 differentially expressed genes (DEGs; false discovery rate <0.05; log-fold change cutoff = 0) from 36,007 expressed Populus gene models. A total of 14,415 DEGs were directly related to transitions between four major developmental phases - growth, senescence initiation, reorganization, and senescence termination. These DEGs were significantly (p?<?0.05) enriched in 279 gene ontology (GO) terms, including those related to photosynthesis, metabolic process, catalytic activity, protein phosphorylation, kinase activity, pollination, and transport. Also, there were 881 differentially expressed transcription factor (TF) genes from 54 TF families, notably bHLH, MYB, ERF, MYB-related, NAC, and WRKY. We also examined 28 DEGs known as alternative splicing (AS) factors that regulate AS process, and found evidence for a reduced level of AS activity during leaf senescence. Furthermore, we were able to identify a number of promoter sequence motifs associated with leaf senescence. This work provides a comprehensive resource for identification of genes involved in seasonal leaf senescence in trees, and informs efforts to explore the conservation and divergence of molecular mechanisms underlying leaf senescence between annual and perennial species.
Project description:Abiotic stress is a major factor affecting the growth, development, yield and quality in plants including the important biomass yield such as in a bioenergy feedstock crops. In a first of its kind, RNA-seq based high resolution survey of abiotic stress-induced transcriptome of bioenergy feedstock model plant western poplar (Populus trichocarpa accesion Nisqually-1) was carried out by way of 81 libraries made from total RNA isolated from three tissues, mature vascular leaf, stem xylem and root sampled from plants subjected to untreated control and treated with four individual stress treatments cold, heat, drought and high salinity. For every tissue and treatment type including controls, three individual plants were used per treatment as biological replicates. This research project is supported by the DOE Office of Science, Office of Biological and Environmental Research (BER), USA, grant no. DE-SC0008570
Project description:DNA methylation is an important biological form of epigenetic modification, playing key roles in plant development and environmental responses. In this study, we examined single-base resolution methylomes of Populus under control and drought stress conditions using high-throughput bisulfite sequencing for the first time. Our data showed methylation levels of methylated cytosines, upstream2kp, downstream2kb, and repeatitive sequences significantly increased after drought treatment in Populus. Interestingly, methylation in 100 bp upstream of the transcriptional start site (TSS) repressed gene expression, while methylations in 100 – 2000bp upstream of TSS and within the gene body were positively associated with gene expression. Integrated with the transcriptomic data, we found that all cis-splicing genes were non-methylated, suggesting that DNA methylation may not associate with cis-splicing. However, our results showed that 80% of trans-splicing genes were methylated. Moreover, we found 1156 transcription factors (TFs) with reduced methylation and expression levels and 690 TFs with increased methylation and expression levels after drought treatment. These TFs may play important roles in Populus drought stress responses through the changes of DNA methylation. Taken together, these findings may provide valuable new insight into our understanding of the interaction between gene expression and methylation of drought responses in Populus. Methylomes of Poplar response to drought
Project description:This research uses terminal branches from a wild poplar tree to track somatic genetic, epigenetic, and transcriptional changes. Using a multi-omics approach, we aim to identify and describe mutations which arise during the lifetime of a long-lived perennial plant.
Project description:TA inhibits cellulose synthesis but its actual mode of action is unknown. Addition of TA to hybrid poplar (Populus trichocarpa x Populus deltoides) cell suspensions can activate a cellular program leading to cell death. In contrast, it is possible to habituate hybrid poplar cell cultures to grow in the presence of TA levels that would normally induce cell death. This habituation was performed by adding increasing levels of TA to cell cultures at the time of subculture over a period of 12 months. TA-habituated cells were then cultured in the absence of TA for more than 18 months. These cells displayed a reduced size and growth compared to control cells and had fragmented vacuoles filled with electron-dense material. Habituation to TA was associated with changes in the cell wall composition, with a reduction in cellulose and an increase in pectin levels. Remarkably, high level of resistance to TA was maintained in TA-habituated cells even after being cultured in the absence of TA. Moreover, these cells exhibited enhanced resistance to two other inhibitors of cellulose biosynthesis, dichlobenil and isoxaben. Analysis of gene expression in TA-habituated cells using Affymetrix GeneChip Poplar Genome Array revealed that durable resistance to TA is associated with a major and complex reprogramming of gene expression implicating processes such as cell wall synthesis and modification, lignin and flavonoid synthesis, as well as DNA and chromatin modifications. Experiment Overall Design: Each sample was taken from an individual flask of control cells or TA-habituated resistant cells grown without the toxin for 18 months (TA(-)hab cells) that had grown for 5 d after subculture. Six arrays were hybridized, representing 3 arrays per cell type.
Project description:Poplar is a short-rotation woody crop routinely studied because of its importance as a sustainable bioenergy crop. The establishment of a successful poplar plantation partially depends on its rhizosphere, a dynamic zone governed by complex interactions between plant roots and a plethora of commensal, mutualistic, symbiotic, or pathogenic microbes that shape plant fitness. Here, we examined a consortium of ectomycorrhizal fungi and a beneficial Pseudomonas sp. strain GM41 for their effect on plant growth (height, stem girth, leaf, and root growth) and growth rate over time of four poplar genotypes of Populus trichocarpa. We also compare the total organic carbon and plant exometabolites profiles produced by these different poplar genotypes when colonized by the microbial consortium. We determined that when comparing the treatments to the control, plant growth parameters were not significantly different across the poplar genotypes eight weeks post-inoculation. However, total organic carbon and exometabolite profiles were significantly different between the genotypes and due to the treatments. These findings indicate that this microbial consortium can induce early and different signaling responses in poplar.
Project description:Microarray technology was used to assess transcriptome changes in poplar (Populus alba L.) under a realistic simulation of increased UV-B radiation. Plants were UV-Bbe (UV-B biologically effective radiation) supplemented with a dose of 6 kJ/m2/day for 12 hours per day and allowed to recover during the night. Poplar plants were UV-B treated using a refined controlled environment able to guarantee a realistic simulation of natural conditions, especially for light parameters such as presence of background UV-B radiation for control plants and balanced PAR/UV-A/UV-B ratio. A time course experiment was planned to look both at the rapid and delayed response of poplar to UVB; two time points after 3 h (T3h) and 30 h (6th hour of the third day of treatment, T30h) were considered. 4 independent biological replicates were analysed for each time point. Competitive hybridisations were carried out using the PICME 28K microarray. Keywords: Time course experiment, stress response
Project description:Populus deltoides and Populus trichocarpa were exposed to either ambient air or an acute ozone exposure of 200 ppb for 9 hrs and ozone response was profiled for each genotype by hybridising control against ozone-exposed samples per genotype. Keywords: stress response, genotype comparrison, ozone exposure
Project description:affy_pop_2011_08 - poplar estradiol study - genes regulated by PtaZFP2 in absence of mechanical stress - genes regulated by PtaZFP2 after one bending.Species: Populus tremula x Populus alba-The laboratory previously established a poplar transgenic line overexpressing PtaZFP2 under the control of an estradiol-inducible promoter. - the experiment, conducted on 3-month-old hydroponically-grown poplars, consists in the comparison of WT poplars treated with estradiol and the PtaZFP2-overexpressing line treated with estradiol. We also compared unbent and bent PtaZFP2-overexpressing poplars. The applied strain is quantitatively controlled (Coutand & Moulia, 2000, JExpBot; coutand et al., 2009, Plant Physiology) 9 arrays - poplar; time course
Project description:BACKGROUND: SPLs, a family of transcription factors specific to plants, play vital roles in plant growth and development through regulation of various physiological and biochemical processes. Although Populus trichocarpa is a model forest tree, the PtSPL gene family has not been systematically studied. RESULTS: Here we report the identification of 28 full-length PtSPLs, which distribute on 14 P. trichocarpa chromosomes. Based on the phylogenetic relationships of SPLs in P. trichocarpa and Arabidopsis, plant SPLs can be classified into 6 groups. Each group contains at least a PtSPL and an AtSPL. The N-terminal zinc finger 1 (Zn1) of SBP domain in group 6 SPLs has four cysteine residues (CCCC-type), while Zn1 of SPLs in the other groups mainly contains three cysteine and one histidine residues (C2HC-type). Comparative analyses of gene structures, conserved motifs and expression patterns of PtSPLs and AtSPLs revealed the conservation of plant SPLs within a group, whereas among groups, the P. trichocarpa and Arabidopsis SPLs were significantly different. Various conserved motifs were identified in PtSPLs but not found in AtSPLs, suggesting the diversity of plant SPLs. A total of 11 pairs of intrachromosome-duplicated PtSPLs were identified, suggesting the importance of gene duplication in SPL gene expansion in P. trichocarpa. In addition, 18 of the 28 PtSPLs, belonging to G1, G2 and G5, were found to be targets of miR156. Consistently, all of the AtSPLs in these groups are regulated by miR156. It suggests the conservation of miR156-mediated posttranscriptional regulation in plants. CONCLUSIONS: A total of 28 full-length SPLs were identified from the whole genome sequence of P. trichocarpa. Through comprehensive analyses of gene structures, phylogenetic relationships, chromosomal locations, conserved motifs, expression patterns and miR156-mediated posttranscriptional regulation, the PtSPL gene family was characterized. Our results provide useful information for evolution and biological function of plant SPLs.