RESUMEN

BACKGROUND: The DELLA proteins, a class of GA signaling repressors, belong to the GRAS family of plant-specific nuclear proteins. Members of DELLA gene family encode transcriptional regulators with diverse functions in plant development and abiotic stress responses. To date, DELLAs have been identified in various plant species, such as Arabidopsis thaliana, Malus domestica, Populus trichocarpa, and other land plants. Most information of DELLA family genes was obtained from A. thaliana, whereas little is known about the DELLA gene family in blueberry. RESULTS: In this study, we identified three DELLA genes in blueberry (Vaccinium darrowii, VdDELLA) and provided a complete overview of VdDELLA gene family, describing chromosome localization, protein properties, conserved domain, motif organization, and phylogenetic analysis. Three VdDELLA members, containing two highly conserved DELLA domain and GRAS domain, were distributed across three chromosomes. Additionally, cis-acting elements analysis indicated that VdDELLA genes might play a critical role in blueberry developmental processes, hormone, and stress responses. Expression analysis using quantitative real-time PCR (qRT-PCR) revealed that all of three VdDELLA genes were differentially expressed across various tissues. VdDELLA2 was the most highly expressed VdDELLA in all denoted tissues, with a highest expression in mature fruits. In addition, all of the three VdDELLA genes actively responded to diverse abiotic stresses. Based on qRT-PCR analysis, VdDELLA2 might act as a key regulator in V. darrowii in response to salt stress, whereas VdDELLA1 and VdDELLA2 might play an essential role in cold stress response. Under drought stress, all of three VdDELLA genes were involved in mediating drought response. Furthermore, their transiently co-localization with nuclear markers in A. thaliana protoplasts demonstrated their transcriptional regulator roles. CONCLUSIONS: In this study, three VdDELLA genes were identified in V. darrowii genome. Three VdDELLA genes were closely related to the C. moschata DELLA genes, S. lycopersicum DELLA genes, and M. domestica DELLA genes, respectively, indicating their similar biological functions. Expression analysis indicated that VdDELLA genes were highly efficient in blueberry fruit development. Expression patterns under different stress conditions revealed the differentially expressed VdDELLA genes responding to salt, drought, and cold stress. Overall, these results enrich our understanding of evolutionary relationship and potential functions of VdDELLA genes, which provide valuable information for further studies on genetic improvement of the plant yield and plant resistance.

Asunto(s)

RESUMEN

BACKGROUND: Parkinson's disease (PD) is a common central neurodegenerative disease in middle-aged and elderly people. The progressive degeneration and death of dopaminergic neurons leads to insufficient dopamine (DA) neurotransmitters. Acupuncture and moxibustion can alleviate the aging of neurons. Therefore, studying the neuroprotective effects of electroacupuncture (EA) in PD mice is particularly important. METHODS: Intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 20 mg/kg) was used to establish a PD mouse model, and lipopolysaccharide (LPS) was used to induce microglia polarization. Western blotting, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), Nissl staining and immunohistochemistry were used to detect neuronal apoptosis and injury, α-syn expression and microglial accumulation in PD mice. In addition, the levels of serum inflammatory factors were determined using enzyme-linked immunosorbent assay (ELISA). Flow cytometry was used to detect the Ca2+ content. The fluorescein isothiocyanate (FITC) labeling method was used to assess glucose uptake. A reagent kit was used to detect glucose and lactate levels. RESULTS: MPTP induced the selective loss of DA neurons in the SN of mice, altered Ca2+ homeostasis, and induced an inflammatory response. In addition, maintaining Ca2+ homeostasis depends on the activity of transient receptor potential channel 1 (TRPC1). EA therapy promotes TRPC1 expression, which has a negative regulatory effect on sodium-glucose cotransporter 1 (SGLT1). Under the action of EA, TRPC1 protein expression increased, Ca2+ concentrations increased, and the effect of SGLT1 was inhibited, thereby facilitating glucose metabolism, blocking the activation of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway, restraining M1 polarization of microglia, and alleviating the PD process. CONCLUSION: EA promotes TRPC1/Ca2+ pathway activation, inhibits SGLT1-mediated regulation of glucose metabolism and PI3K/AKT pathway activation, inhibits microglial M1 polarization, and alleviates PD.

RESUMEN

BACKGROUND: WOX genes are a class of plant-specific transcription factors. The WUSCHEL-related homeobox (WOX) family is a member of the homeobox transcription factor superfamily. Previous studies have shown that WOX members play important roles in plant growth and development. However, studies of the WOX gene family in blueberry plants have not been reported. RESULTS: In order to understand the biological function of the WOX gene family in blueberries, bioinformatics were used methods to identify WOX gene family members in the blueberry genome, and analyzed the basic physical and chemical properties, gene structure, gene motifs, promoter cis-acting elements, chromosome location, evolutionary relationships, expression pattern of these family members and predicted their functions. Finally, 12 genes containing the WOX domain were identified and found to be distributed on eight chromosomes. Phylogenetic tree analysis showed that the blueberry WOX gene family had three major branches: ancient branch, middle branch, and WUS branch. Blueberry WOX gene family protein sequences differ in amino acid number, molecular weight, isoelectric point and hydrophobicity. Predictive analysis of promoter cis-acting elements showed that the promoters of the VdWOX genes contained abundant light response, hormone, and stress response elements. The VdWOX genes were induced to express in both stems and leaves in response to salt and drought stress. CONCLUSIONS: Our results provided comprehensive characteristics of the WOX gene family and important clues for further exploration of its role in the growth, development and resistance to various stress in blueberry plants.

Asunto(s)

RESUMEN

Introduction: Hybrid poplars are industrial trees in China. An understanding of the molecular mechanism underlying wood formation in hybrid poplars is necessary for molecular breeding. Although the division and differentiation of vascular cambial cells is important for secondary growth and wood formation, the regulation of this process is largely unclear. Methods: In this study, mPagGRF15 OE and PagGRF15-SRDX transgenic poplars were generated to investigate the function of PagGRF15. RNA-seq and qRT-PCR were conducted to analyze genome-wide gene expression, while ChIP‒seq and ChIP-PCR were used to identified the downstream genes regulated by PagGRF15. Results and discussion: We report that PagGRF15 from hybrid poplar (Populus alba × P. glandulosa), a growth-regulating factor, plays a critical role in the regulation of vascular cambium activity. PagGRF15 was expressed predominantly in the cambial zone of vascular tissue. Overexpression of mPagGRF15 (the mutated version of GRF15 in the miR396 target sequence) in Populus led to decreased plant height and internode number. Further stem cross sections showed that the mPagGRF15 OE plants exhibited significant changes in vascular pattern with an increase in xylem and a reduction in phloem. In addition, cambium cell files were decreased in the mPagGRF15 OE plants. However, dominant suppression of the downstream genes of PagGRF15 using PagGRF15-SRDX showed an opposite phenotype. Based on the RNA-seq and ChIP-seq results, combining qRT-PCR and ChIP-PCR analysis, candidate genes, such as WOX4b, PXY and GID1.3, were obtained and found to be mainly involved in cambial activity and xylem differentiation. Accordingly, we speculated that PagGRF15 functions as a positive regulator mediating xylem differentiation by repressing the expression of the WOX4a and PXY genes to set the pace of cambial activity. In contrast, PagGRF15 mediated the GA signaling pathway by upregulating GID1.3 expression to stimulate xylem differentiation. This study provides valuable information for further studies on vascular cambium differentiation mechanisms and genetic improvement of the specific gravity of wood in hybrid poplars.

RESUMEN

The phytohormone salicylic acid (SA) plays a crucial role in plant growth and development. However, the mechanism of high-concentration SA-affected gravitropic response in plant root growth and root hair development is still largely unclear. In this study, wild-type, pin2 mutant and various transgenic fluorescence marker lines of Arabidopsis thaliana were investigated to understand how root growth is affected by high SA treatment under gravitropic stress conditions. We found that exogenous SA application inhibited gravitropic root growth and root hair development in a dose-dependent manner. Further analyses using DIRECT REPEAT5 (DR5)-GFP, auxin sensor DII-VENUS, auxin efflux transporter PIN2-GFP, trans-Golgi network/early endosome (TGN/EE) clathrin-light-chain 2 (CLC2)-mCherry and prevacuolar compartment (PVC) (Rha1)-mCherry transgenic marker lines demonstrated that high SA treatment severely affected auxin accumulation, root-specific PIN2 distribution and PIN2 gene transcription and promoted the vacuolar degradation of PIN2, possibly independent of clathrin-mediated endocytic protein trafficking. Our findings proposed a new underlying mechanism of SA-affected gravitropic root growth and root hair development via the regulation of PIN2 gene transcription and PIN2 protein endocytosis in plants.

Asunto(s)

RESUMEN

Cytochrome P450 monooxygenases (CYP450s) play crucial roles in the regulation of plant growth and response to abiotic stress. However, their functions in woody trees are still largely unknown. Previously, we reported that expression of the rice cytochrome P450 monooxygenase gene OsCYP714D1 increased gibberellic acid (GA) accumulation and shoot growth in transgenic poplar. In this work, we demonstrate that expression of OsCYP714D1 improved the salt tolerance of transgenic poplar plants. Compared to wild type, plant height and K+ content were significantly higher, whereas plant growth inhibition and Na+ content were significantly lower, in transgenic plants grown under high salt stress condition. Transcriptomic analyses revealed that OsCYP714D1 expression up-regulated the expressions of GA biosynthesis, signaling and stress responsive genes in transgenic plants under both normal and high salt stress conditions. Further gene ontology (GO) analyses indicated that genes involved in plant hormone and ion metabolic activities were significantly enriched in transgenic plants. Our findings imply that OsCYP714D1 participated in the regulation of both shoot growth and salt resistance through regulating gibberellin and ion homeostasis in transgenic poplar, and it can be used as a candidate gene for the engineering of new tree varieties with improved biomass production and salt stress resistance.

Asunto(s)

RESUMEN

Growth-regulating factors (GRFs) are important regulators of plant development and growth, but their possible roles in xylem development in woody plants remain unclear. Here, we report that Populus alba × Papulus glandulosa PagGRF12a negatively regulates xylem development in poplar. PagGRF12a is expressed in vascular tissues. Compared to non-transgenic control plants, transgenic poplar plants overexpressing PagGRF12a exhibited reduced xylem width and plants with repressed expression of PagGRF12a exhibited increased xylem width. Xylem NAC domain 1 (XND1) encodes a NAC domain transcription factor that regulates xylem development and transcriptional analyses revealed that PagXND1a is highly upregulated in PagGRF12a-overexpressing plants and downregulated in PagGRF12a-suppressed plants, indicating that PagGRF12a may regulate xylem development through PagXND1a. Transient transcriptional assays and chromatin immunoprecipitation-polymerase chain reaction assays confirmed that PagGRF12a directly upregulates PagXND1a. In addition, PagGRF12a interacts with the GRF-Interacting Factor (GIF) PagGIF1b, and this interaction enhances the effects of PagGRF12a on PagXND1a. Our results indicate that PagGRF12a inhibits xylem development by upregulating the expression of PagXND1a.

Asunto(s)

RESUMEN

Inflammation plays a pivotal role in promoting the pathophysiology of ischemic stroke (IS). Microglia is the major immunocompetent cells involved in different neuropathologies. The activation of cyclic GMP-AMP synthase (cGAS) and its downstream signaling protein-stimulator of interferon genes (STING) is increasingly recognized as a crucial determinant of neuropathophysiology. However, the mechanisms underlying cGAS-STING signaling regulating inflammatory response during IS remains to be elucidated. In this study, HT22 cells was used to establish an oxygen-glucose deprivation (OGD) cell model in vitro, and then this cell culture supernatant containing OGD-induced DAMPs (OIDs) was employed to stimulate BV2 microglia. Furthermore, a middle cerebral artery occlusion (MCAO) mouse model was established. Cells and MCAO mice were treated with si-cGAS or si-NC lentivirus. The expression levels of STING, cGAS and p-IRF3 in BV2 cells or MCAO mouse brain; the microglial M1/M2 polarization of BV2 microglia or isolated microglial cells from MCAO mouse brain; the contents of iNOS, TNF-α, TGF-ß and IL-10 in the culture medium of BV2 cells or in murine brain homogenates, were all detected. In addition, the severity of cerebral infarction with or without the knockdown of cGAS in a MCAO mouse model was also determined by TTC staining. Results showed that OGD-induced DAMPs strongly activated cGAS-STING pathway and triggered microglia polarization in BV2 cells, reflecting as the accumulation of a plethora of pro-inflammatory factors in activated microglia. However, these effects could be inhibited by cGAS knockdown. In the MCAO mouse model, the inhibition of cGAS-STING pathway resulted from cGAS knockdown could effectively diminish cell apoptosis in mouse brain stimulated by MIDs (MCAO-induced DAMPs), reduced the area ratio of cerebral infarction and ultimately improved the injured nerve function during IS. Taken together, our elucidation of underlying mechanisms involved in the microglial inflammatory response, triggered by cGAS-STING signaling, highlights this pathway as a potential therapeutic target in IS.

Asunto(s)

RESUMEN

OBJECTIVE: To evaluate the efficacy of the second operation within 1 week after ineffective microvascular decompression (MVD) for patients with primary hemifacial spasm (HFS), and to find out the causes of failure. METHODS: The surgery records and postoperative follow-ups of 52 primary HFS patients who had poor relief of spasm after their first MVDs were investigated. Patients were divided into 2 groups. Group A included 46 patients (16 males and 30 females) that went through the second operation within 1 week after the failure of the first MVD. Group B included 6 patients (3 males and 3 females) which did not take the reoperation. The level of spasm of each patient was then re-evaluated 1 year after the first surgery. RESULTS: Among 52 patients who had poor relief after the first MVD between April 2016 and October 2019, 46 patients underwent a second MVD within 1 week while 6 patients refused to take the reoperation. Their mean duration of HFS was 102.4 ±â€Š57.9 months. During reoperations for patients in group A, we discovered additional sites of neurovascular compression in 11 cases (23.91%). Forty-five patients (97.82%) in group A achieved complete relief 1 year after the second surgery while there was 1 recurrent case. Four patients (66.67%) in group B achieved delayed relief 1 year after the first surgery, while the other 2 patients were still suffering facial spasm in the 1-year follow-up. Group A demonstrated higher relief rate compared to group B in the 1 year follow up (P = 0.032). Although no severe complications occurred on patients in both group, 4 of them suffered grade II facial palsy, and another 3 patients had developed mild temporary hearing loss on the operation side. CONCLUSION: The second operation within 1 week after an ineffective MVD is safe and effective. Full revealing of root exit zone and making sure no neurovascular compression missed with abnormal muscle response monitoring are the keys to a successful MVD.

Asunto(s)

RESUMEN

BACKGROUND: Growth-regulating factors (GRFs) are plant-specific transcription factors that control organ size. Nineteen GRF genes were identified in the Populus trichocarpa genome and one was reported to control leaf size mainly by regulating cell expansion. In this study, we further characterize the roles of the other poplar GRFs in leaf size control in a similar manner. RESULTS: The 19 poplar GRF genes were clustered into six groups according to their phylogenetic relationship with Arabidopsis GRFs. Bioinformatic analysis, degradome, and transient transcription assays showed that 18 poplar GRFs were regulated by miR396, with GRF12b the only exception. The functions of PagGRF6b (Pag, Populus alba × P. glandulosa), PagGRF7a, PagGRF12a, and PagGRF12b, representing three different groups, were investigated. The results show that PagGRF6b may have no function on leaf size control, while PagGRF7a functions as a negative regulator of leaf size by regulating cell expansion. By contrast, PagGRF12a and PagGRF12b may function as positive regulators of leaf size control by regulating both cell proliferation and expansion, primarily cell proliferation. CONCLUSIONS: The diversity of poplar GRFs in leaf size control may facilitate the specific, coordinated regulation of poplar leaf development through fine adjustment of cell proliferation and expansion.

Asunto(s)

RESUMEN

Paper mulberry, a vigorous pioneer species used for ecological reclamation and a high-protein forage plant for economic development, has been widely planted in China. To further develop its potential value, it is necessary to explore the regulatory mechanism of nitrogen metabolism for rational nitrogen utilization. In this study, we investigated the morphology, physiology and transcriptome of a paper mulberry hybrid (Broussonetia kazinoki × B. papyrifera) in response to different nitrogen concentrations. Moderate nitrogen promoted plant growth and biomass accumulation. Photosynthetic characteristics, concentration of nitrogenous compounds and activities of enzymes were stimulated under nitrogen treatment. However, these enhancements were slightly or severely inhibited under excessive nitrogen supply. Nitrite reductase and glutamate synthase were more sensitive than nitrate reductase and glutamine synthetase and more likely to be inhibited under high nitrogen concentrations. Transcriptome analysis of the leaf transcriptome identified 161,961 unigenes. The differentially expressed genes associated with metabolism of nitrogen, alanine, aspartate, glutamate and glycerophospholipid showed high transcript abundances after nitrogen application, whereas those associated with glycerophospholipid, glycerolipid, amino sugar and nucleotide sugar metabolism were down-regulated. Combined with weighted gene coexpression network analysis, we uncovered 16 modules according to similarity in expression patterns. Asparagine synthetase and inorganic pyrophosphatase were considered two hub genes in two modules, which were associated with nitrogen metabolism and phosphorus metabolism, respectively. The expression characteristics of these genes may explain the regulation of morphological, physiological and other related metabolic strategies harmoniously. This multifaceted study provides valuable insights to further understand the mechanism of nitrogen metabolism and to guide utilization of paper mulberry.

Asunto(s)

RESUMEN

Wood formation is the terminal differentiation of xylem mother cells derived from cambial initials, and negative regulators play important roles in xylem differentiation. The molecular mechanism of the negative regulator of xylem differentiation PagKNAT2/6b was investigated. PagKNAT2/6b is an ortholog of Arabidopsis KNAT2 and KNAT6 that is highly expressed in phloem and xylem. Compared to nontransgenic control plants, transgenic poplar plants overexpressing PagKNAT2/6b present with altered vascular patterns, characterized by decreased secondary xylem with thin cell walls containing less cellulose, xylose and lignin. RNA sequencing analyses revealed that differentially expressed genes are enriched in xylem differentiation and secondary wall synthesis functions. Expression of NAM/ATAF/CUC (NAC) domain genes including PagSND1-A1, PagSND1-A2, PagSND1-B2 and PagVND6-C1 is downregulated by PagKNAT2/6b, while PagXND1a is directly upregulated. Accordingly, the dominant repression form of PagKNAT2/6b leads to increased xylem width per stem diameter through downregulation of PagXND1a. PagKNAT2/6b can inhibit cell differentiation and secondary wall deposition during wood formation in poplar by modulating the expression of NAC domain transcription factors. Direct activation of PagXND1a by PagKNAT2/6b is a key node in the negative regulatory network of xylem differentiation by KNOXs.

Asunto(s)

RESUMEN

Adventitious roots occur naturally in many species and can also be induced from explants of some tree species including Populus, providing an important means of clonal propagation. Auxin has been identified as playing a crucial role in adventitious root formation, but the associated molecular regulatory mechanisms need to be elucidated. In this study, we examined the role of PagFBL1, the hybrid poplar (Populus alba × P. glandulosa clone 84K) homolog of Arabidopsis auxin receptor TIR1, in adventitious root formation in poplar. Similar to the distribution pattern of auxin during initiation of adventitious roots, PagFBL1 expression was concentrated in the cambium and secondary phloem in stems during adventitious root induction and initiation phases, but decreased in emerging adventitious root primordia. Overexpressing PagFBL1 stimulated adventitious root formation and increased root biomass, while knock-down of PagFBL1 transcript levels delayed adventitious root formation and decreased root biomass. Transcriptome analyses of PagFBL1 overexpressing lines indicated that an extensive remodelling of gene expression was stimulated by auxin signalling pathway during early adventitious root formation. In addition, PagIAA28 was identified as downstream targets of PagFBL1. We propose that the PagFBL1-PagIAA28 module promotes adventitious rooting and could be targeted to improve Populus propagation by cuttings.

Asunto(s)

RESUMEN

Growth-regulating factors (GRFs) are involved in various developmental events, particularly leaf development. However, the functions of GRFs in woody plants remain elusive. In this study, functional characterization of GRF15 in Populus was performed. Most GRFs are preferentially expressed in young leaves. As GRF15 was expressed at the highest level and with highest ratio in Populus species with large leaves, this gene was investigated through transgenic analyses. Promotor-ß-glucuronidase analysis revealed expression of GRF15 at the leaf expansion zone. Additionally, GRF15 was found to be localized in the nucleus and regulated by miR396. Leaf size and palisade cell size were significantly increased and decreased in GRF15-overexpressing and dominant repression lines, respectively. Consistently, expression of EXPA11a, a homolog of cell-expansion marker EXPA11 in Arabidopsis, was strongly upregulated and downregulated in the GRF15-overexpressing and dominant repression lines, respectively, which was further manifested by activation of EXPA11a by GRF15 in transactivation assays. Therefore, GRF15 is required for leaf size control and primarily modulates cell expansion during leaf development in Populus.

Asunto(s)

RESUMEN

OBJECTIVE: ?To compare the effects on the osteogenesis of bone marrow mesenchymal stem cells (BMSCs) between hypoxia and hypoxia mimetic agents dimethyloxalylglycine (DMOG) under normal oxygen condition. METHODS: ?BMSCs were isolated and cultured from healthy 3-4 weeks old Kunming mouse. Cell phenotype of CD29, CD44, CD90, and CD34 was assayed with flow cytometry; after osteogenic, adipogenic, and chondrogenic induction, alizarin red staining, oil red O staining, and toluidine blue staining were performed. The passage 3 BMSCs were cultured under normal oxygen in control group (group A), under 1%O2 in hypoxia group (group B), and under normal oxygen and 0.5 mmol/L DMOG in DMOG intervention group (group C). BMSCs proliferation was estimated by methyl thiazolyl tetrazolium assay at 1, 2, 3, and 4 days. Alkaline phophatase (ALP) expression was determined at 7 and 14 days after osteogenic induction. Western blot was employed for detecting hypoxia inducible factor-1α (HIF-1α) at 24 hours. Real time fluorescence quantitative PCR was employed for detecting the mRNA expression of runt-related transcription factor 2 (RUNX2) and Osterix at 3 and 7 days. Alizarin red staining was applied to assess the deposition of calcium tubercle at 21 days. RESULTS: ?The BMSCs presented CD29(+), CD44(+), CD90(+), and CD34(-); and results of the alizarin red staining, oil red O staining, and toluidine blue staining were positive after osteogenic, adipogenic, and chondrogenic induction. No significant difference in BMSCs proliferation was observed among 3 groups at 1 day (P>0.05); compared with group A, BMSCs proliferation was inhibited in group C at 2, 3, and 4 days, but no significant difference was observed (P>0.05); compared with group A, BMSCs proliferation was significantly promoted in group B (P<0.05). At each time point, compared with group A, the ALP expression, HIF-1α protein relative expression, and mRNA relative expressions of RUNX2 and Osterix were significantly up-regulated in groups B and C (P<0.05); compared with group B, the ALP expression, the RUNX2 and Osterix mRNA relative expression were significantly up-regulated in group C (P<0.05); compared with group C, the HIF-1α protein relative expression was significantly up-regulated in group B (P<0.05). The alizarin red staining showed little red staining materials in group A, some red staining materials in group B, and a large number of red staining materials in group C. CONCLUSIONS: ?Hypoxia can promote BMSCs proliferation, DMOG can not influence the BMSCs proliferation; both hypoxia and DMOG can improve osteogenic differentiation of BMSCs, and DMOG is better than hypoxia in improving the BMSCs osteogenesis.

RESUMEN

The plant hormone auxin is a central regulator of plant growth. TRANSPORT INHIBITOR RESPONSE 1/AUXIN SIGNALING F-BOX (TIR1/AFB) is a component of the E3 ubiquitin ligase complex SCF(TIR1/AFB) and acts as an auxin co-receptor for nuclear auxin signaling. The SCF(TIR1/AFB)-proteasome machinery plays a central regulatory role in development-related gene transcription. Populus trichocarpa, as a model tree, has a unique fast-growth trait to which auxin signaling may contribute. However, no systematic analyses of the genome organization, gene structure, and expression of TIR1-like genes have been undertaken in this woody model plant. In this study, we identified a total of eight TIR1 genes in the Populus genome that are phylogenetically clustered into four subgroups, PtrFBL1/PtrFBL2, PtrFBL3/PtrFBL4, PtrFBL5/PtrFBL6, and PtrFBL7/PtrFBL8, representing four paralogous pairs. In addition, the gene structure and motif composition were relatively conserved in each paralogous pair and all of the PtrFBL members were localized in the nucleus. Different sets of PtrFBLs were strongly expressed in the leaves, stems, roots, cambial zones, and immature xylem of Populus. Interestingly, PtrFBL1 and 7 were expressed mainly in vascular and cambial tissues, respectively, indicating their potential but different roles in wood formation. Furthermore, Populus FBLs responded differentially upon exposure to various stresses. Finally, over-expression studies indicated a role of FBL1 in poplar stem growth and response to drought stress. Collectively, these observations lay the foundation for further investigations into the potential roles of PtrFBL genes in tree growth and development.