Project description:To identify genes that are drought-responsive we conducted drought (soil water depletion) experiments on 3-month-old *P*. *trichocarpa *clonal plants. The plants undergo five different stages based on the appearance of their shoots and leaves during the drought experiments. Stage I: The shoot and leaves are green, and the leaves are well-spread. Stage II: The leaves are droopy. Stage III: The shoot is droopy, and the leaves are partially dry. Stage IV: The leaves are brown and totally dry. Stage V: The shoot is brown. With fully irrigation, the soil water content is 74% and the xylem water content is 80.6%. Plants in Stage III (Day 5) are under a mild drought state. The soil and xylem water content in Stage III dropped to 33% and 75.3%, respectively. Stage IV (Day 6-10) is a severe drought state where the soil and xylem water content continued decreasing to 29% and 74.3%, respectively in Day 7. The stressed plants from Stage I-IV could all recover in 3 days after rehydration, but the plants in Stage V could not recover after rehydration.
Project description:A COMPASS histone H3K4 trimethyltransferase pentamer transactivates drought tolerance and growth/biomass production in Populus trichocarpa
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.
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:PtrHSFB3-1 and PtrMYB092 are xylem specific genes in xylem of P. trichocarpa, and their expression levels are down regulated most significantly in tension wood. These two transcription factors were transiently overexpressed in stem differentiating xylem (SDX) of P. trichocarpa , and transcriptomic sequencing was performed to identify the regulatory effects of the two transcription factors on wood formation related genes.
Project description:Brassinosteroids (BRs) are essential hormones that play crucial roles in plant growth, reproduction and response to abiotic and biotic stress. In Arabidopsis, AtCYP85A2 works as a bifunctional cytochrome P450 monooxygenase to catalyse the conversion of castasterone to brassinolide, a final rate-limiting step in the BR-biosynthetic pathway. Here, we report the functional characterizations of PtCYP85A3, one of the three AtCYP85A2 homologous genes from Populus trichocarpa. PtCYP85A3 shares the highest similarity with AtCYP85A2 and can rescue the retarded-growth phenotype of the Arabidopsis cyp85a2-2 and tomato dx mutants. Constitutive expression of PtCYP85A3, driven by the cauliflower mosaic virus 35S promoter, increased the endogenous BR levels and significantly promoted the growth and biomass production in both transgenic tomato and poplar. Compared to the wild type, plant height, shoot fresh weight and fruit yield increased 50%, 56% and 43%, respectively, in transgenic tomato plants. Similarly, plant height and stem diameter increased 15% and 25%, respectively, in transgenic poplar plants. Further study revealed that overexpression of PtCYP85A3 enhanced xylem formation without affecting the composition of cellulose and lignin, as well as the cell wall thickness in transgenic poplar. Our finding suggests that PtCYP85A3 could be used as a potential candidate gene for engineering fast-growing trees with improved wood production.
Project description:We report on the genome-wide distribution pattern of histone H3 lysine 9 acetylation (H3K9ac) and the pattern’s association with whole genome expression profiles in Populus trichocarpa subjected to soil-water depletion. We identified a set of drought responsive genes whose expression is directly regulated by differential modification of H3K9ac.
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 40â45 %) and the water-limited group (soil volumetric water content of 10â15 %). Two cDNA libraries constructed separately from the WW and WL groups were subjected to high-throughput Illumina sequencing.
Project description:Small RNAs (21-24 nt) are pivotal regulators of gene expression that guide both transcriptional and post-transcriptional silencing mechanisms in diverse eukaryotes, including most if not all plants. MicroRNAs (miRNAs) and short interfering RNAs (siRNAs) are the two major types, both of which have a demonstrated and important role in plant development, stress responses and pathogen resistance. In this work, we used a deep sequencing approach (Sequencing-By-Synthesis, or SBS) to develop sequence resources of small RNAs from Populus trichocarpa tissues (including leaves, xylem and mechanically-treated xylem). The high depth of the resulting datasets enabled us to examine in detail critical small RNA features as size distribution, tissue-specific regulation and sequence conservation between different organs in this species. We also developed database resources and a dedicated website (http://smallrna.udel.edu/) with computational tools for allowing other users to identify new miRNAs or siRNAs involved in specific regulatory pathways, verify the degree of conservation of these sequences in other plant species and map small RNAs on genes or larger regions of the maize genome under study.
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