Growth-regulating factor 15-mediated gene regulatory network enhances salt tolerance in poplar.

Soil salinity is an important determinant of crop productivity and triggers salt stress response pathways in plants. The salt stress response is controlled by transcriptional regulatory networks that maintain regulatory homeostasis through combinations of transcription factor (TF)-DNA and TF-TF interactions. We investigated the transcriptome of poplar 84 K (Populus alba × Populus glandulosa) under salt stress using samples collected at 4- or 6-h intervals within 2 days of salt stress treatment. We detected 24,973 differentially expressed genes, including 2,231 TFs that might be responsive to salt stress. To explore these interactions and targets of TFs in perennial woody plants, we combined gene regulatory networks, DNA affinity purification sequencing, yeast two-hybrid-sequencing, and multi-gene association approaches. Growth-regulating factor 15 (PagGRF15) and its target, high-affinity K+ transporter 6 (PagHAK6), were identified as an important regulatory module in the salt stress response. Overexpression of PagGRF15 and PagHAK6 in transgenic lines improved salt tolerance by enhancing Na+ transport and modulating H2O2 accumulation in poplar. Yeast two-hybrid assays identified more than 420 PagGRF15-interacting proteins, including ETHYLENE RESPONSE FACTOR TFs and a zinc finger protein (C2H2) that are produced in response to a variety of phytohormones and environmental signals and are likely involved in abiotic stress. Therefore, our findings demonstrate that PagGRF15 is a multifunctional TF involved in growth, development, and salt stress tolerance, highlighting the capability of a multifaceted approach in identifying regulatory nodes in plants.

The transcriptional landscape of Populus pattern/effector-triggered immunity and how PagWRKY18 involved in it.

Plants trigger a robust immune response by activating massive transcriptome reprogramming through crosstalk between PTI and ETI. However, how PTI and ETI contribute to the quantitative or/and qualitative output of immunity and how they work together when both are being activated were unclear. In this study, we performed a comprehensive overview of pathogen-triggered transcriptomic reprogramming by analyzing temporal changes in the transcriptome up to 144 h after Colletotrichum gloeosporioides inoculated in Populus. Moreover, we constructed a hierarchical gene regulatory network of PagWRKY18 and its potential target genes to explore the underlying regulatory mechanisms of PagWRKY18 that are not yet clear. Interestingly, we confirmed that PagWRKY18 protein can directly bind the W-box elements in the promoter of a transmembrane leucine-rich repeat receptor-like kinase, PagSOBIR1 gene, to trigger PTI. At the same time, PagWRKY18 functions in disease tolerance by modulation of ROS homeostasis and induction of cell death via directly targeting PagGSTU7 and PagPR4 respectively. Furthermore, PagPR4 can interact with PagWRKY18 to inhibit the expression of PagPR4 genes, forming a negative feedback loop. Taken together, these results suggest that PagWRKY18 may be involved in regulating crosstalk between PTI and ETI to activate a robust immune response and maintain intracellular homeostasis.

Interlayer coupled dual-layer metagratings for broadband and high-efficiency anomalous reflection.

Recent progress in metagratings highlights the promise of high-performance wavefront engineering devices, notably for their exterior capability to steer beams with near-unitary efficiency. However, the narrow operating bandwidth of conventional metagratings remains a significant limitation. Here, we propose and experimentally demonstrate a dual-layer metagrating, incorporating enhanced interlayer couplings to realize high-efficiency and broadband anomalous reflection within the microwave frequency band. The metagrating facilitated by both intralayer and interlayer couplings is designed through the combination of eigenmode expansion (EME) algorithm and particle swarm optimization (PSO) to significantly streamline the computational process. Our metagrating demonstrates the capacity to reroute a normally incident wave to +1 order diffraction direction across a broad spectrum, achieving an average efficiency approximately 90% within the 14.7 to 18 GHz range. This study may pave the way for future applications in sophisticated beam manipulations, including spatial dispersive devices, by harnessing the intricate dynamics of multi-layer metagratings with complex interlayer and intralayer interactions.

A transcriptional cascade mediated by two APETALA2 family members orchestrates carotenoid biosynthesis in tomato.

Carotenoids are important nutrients for human health that must be obtained from plants since they cannot be biosynthesized by the human body. Dissecting the regulatory mechanism of carotenoid metabolism in plants represents the first step toward manipulating carotenoid contents in plants by molecular design breeding. In this study, we determined that SlAP2c, an APETALA2 (AP2) family member, acts as a transcriptional repressor to regulate carotenoid biosynthesis in tomato (Solanum lycopersicum). Knockout of SlAP2c in both the "MicroTom" and "Ailsa Craig" backgrounds resulted in greater lycopene accumulation, whereas overexpression of this gene led to orange-ripe fruit with significantly lower lycopene contents than the wild type. We established that SlAP2c represses the expression of genes involved in lycopene biosynthesis by directly binding to the cis-elements in their promoters. Moreover, SlAP2c relies on its EAR motif to recruit the co-repressors TOPLESS (TPL)2/4 and forms a complex with histone deacetylase (had)1/3, thereby reducing the histone acetylation levels of lycopene biosynthesis genes. Furthermore, SlAP2a, a homolog of SlAP2c, acts upstream of SlAP2c and alleviates the SlAP2c-induced repression of lycopene biosynthesis genes by inhibiting SlAP2c transcription during fruit ripening. Therefore, we identified a transcriptional cascade mediated by AP2 family members that regulates lycopene biosynthesis during fruit ripening in tomato, laying the foundation for the manipulation of carotenoid metabolism in plants.

High-speed ADC based on photonic time-stretched technology with dispersion-tunable CFBG.

We propose a photonic time-stretched analog-to-digital converter (PTS-ADC) based on dispersion-tunable chirped fiber Bragg grating (CFBG), by demonstrating a economical ADC system with seven different stretch factors. The stretch factors are tunable by changing the dispersion of CFBG, in order to obtain different sampling points. Accordingly, the total sampling rate of the system can be improved. Only a single channel is required to increase the sampling rate and achieve the effect of multi-channel sampling. Finally, seven groups of different stretch factors ranging from 1.882 to 2.206 are obtained, which are equivalent to seven groups of different sampling points. We successfully recover the input radio frequency (RF) signals with frequencies from 2 GHz to 10 GHz. In addition, the sampling points are increased by 14.4 times and the equivalent sampling rate is increased to 288 GSa/s. The proposed scheme is suitable for commercial microwave radar systems, which can obtain a much higher sampling rate at a low cost.

Design of arbitrary energy distribution beam splitters base on multilayer metagratings by a hybrid evolutionary particle swarm optimization.

Multilayer metagratings have strong wavefront manipulation capabilities and find important applications in beam splitters. Traditional methods rely on the phase gradient design of generalized Snell's law, which can achieve highly efficient beam splitters with uniform energy distribution. However, designing arbitrary energy distributions in different channels under two orthogonal polarizations remains a challenge because it requires more complex structures to modulate the energy flow. In this work, we employed a hybrid evolutionary particle swarm optimization (HEPSO) from the combination of particle swarm optimization (PSO) and genetic algorithm (GA) which has a strong ability to find the optimal structures that satisfy the specific energy flow distributions. We used the crossover and mutation operators of GA to improve the global search capabilities, and the velocity updating formula of PSO to replace the selection operator of GA to avoid local optimization. Using this approach, we successfully designed a uniform beam splitter with an efficiency of over 90% and two beam splitters with arbitrary energy distributions, achieving an average error of about 0.5%. The optimal and average efficiencies obtained from running 10 optimizations are 2.2% and 4% higher than those obtained using PSO alone with 30 populations and 75 iterations. We envision that the proposed method can also provide an idea for other photonics design problems.

Accelerated organic matter decomposition in thermokarst lakes upon carbon and phosphorus inputs.

Mineralization of dissolved organic matter (DOM) in thermokarst lakes plays a non-negligible role in the permafrost carbon (C) cycle, but remains poorly understood due to its complex interactions with external C and nutrient inputs (i.e., aquatic priming and nutrient effects). Based on large-scale lake sampling and laboratory incubations, in combination with 13 C-stable-isotope labeling, optical spectroscopy, and high-throughput sequencing, we examined large-scale patterns and dominant drivers of priming and nutrient effects of DOM biodegradation across 30 thermokarst lakes along a 1100-km transect on the Tibetan Plateau. We observed that labile C and phosphorus (P) rather than nitrogen (N) inputs stimulated DOM biodegradation, with the priming and P effects being 172% and 451% over unamended control, respectively. We also detected significant interactive effects of labile C and nutrient supply on DOM biodegradation, with the combined labile C and nutrient additions inducing stronger microbial mineralization than C or nutrient treatment alone, illustrating that microbial activity in alpine thermokarst lakes is co-limited by both C and nutrients. We further found that the aquatic priming was mainly driven by DOM quality, with the priming intensity increasing with DOM recalcitrance, reflecting the limitation of external C as energy sources for microbial activity. Greater priming intensity was also associated with higher community-level ribosomal RNA gene operon (rrn) copy number and bacterial diversity as well as increased background soluble reactive P concentration. In contrast, the P effect decreased with DOM recalcitrance as well as with background soluble reactive P and ammonium concentrations, revealing the declining importance of P availability in mediating DOM biodegradation with enhanced C limitation but reduced nutrient limitation. Overall, the stimulation of external C and P inputs on DOM biodegradation in thermokarst lakes would amplify C-climate feedback in this alpine permafrost region.

Rhodaelectro-Catalyzed Decarboxylative Cross-Dehydrogenative Coupling of Indole-3-carboxylic Acids and Olefins via Weakly Coordinating Carboxyl Groups.

A rhodaelectro-catalyzed C2-H selectively decarboxylative alkenylation of 3-carboxy-1H-indoles employing electricity as the traceless terminal oxidant has been accomplished. The weakly coordinating carboxyl group serves as the traceless directing groups. External oxidant-free in an undivided cell with constant current in aqueous solution ensures the decarboxylative C-H alkenylation to be viable and sustainable.

Target and Mechanism of the Xihuang Pill Based on Network Pharmacology for Lung Squamous Cell Carcinoma.

Context: Lung squamous cell carcinoma (LUSC) accounts for 30% of non-small-cell lung cancers (NSCLC), and an effective pharmacological treatment for LUSC isn't yet available. The Xihuang Pill is a potent Chinese medicinal preparation widely prescribed for the management of LUSC. Objective: The study intended to use the network-pharmacology method to ascertain the effective active ingredients, targets of action, and cellular-signal transduction involved in the prevention and treatment of LUSC when using the Xihuang Pill and to identify the mechanism of action of the pills against LUSC, to provide a more adequate scientific basis for subsequent studies. Design: The research team performed a genetic study. Setting: The study took place at Shanghai. Outcome Measures: The research team: (1) created the feature sets, for both the LUSC and normal features, using the Cancer Genome Atlas' (TCGA's) LUSC dataset; (2) performed a weighted correlation network analysis (WGCNA) of the differentially expressed genes (DEGs) using the R package WGCNA; (3) searched for the chemical components of the Xihuang Pill using the Traditional Chinese Medicine Systematic Pharmacology Database and Analysis Platform (TCMSP) and the Herb Group Identification Platform, and (4) selected the novel the Matthews correlation coefficient (MCC) algorithm to screen the hub genes. Results: The study found 8713 DEGs between the LUSC and normal groups. The top ten, important, downregulated genes included: (1) advanced glycosylation end product (AGER), (2) chitinase, acidic pseudogene 2 (CHIAP2), (3) CD300 molecule like family member G (CD300LG), (4) solute carrier family 6 member 4 (SLC6A4), (5) carboxypeptidase B2 (CPB2), (6) claudin 18 (CLDN18), (7) gamma-glutamyltransferase light chain 1 (GGTLC1), (8) gastrokine 2 (GKN2), (9) progastricsin (PGC), and (10) pulmonary surfactant-associated protein C (SFTPC). The top 10 upregulated genes included: (1) cancer susceptibility 9 (CASC9), (2) homeobox C13 (HOXC13), (3) keratin 6a (KRT6A), (4) desmoglein 3 (DSG3), (5) keratin 16 (KRT16), (6) forkhead box E1 (FOXE1), (7) preferentially expressed antigen in melanoma (PRAME), (8) calmodulin-like protein 3 (CALML3), (9) KRT68, and (10) aldo-keto reductase family 1 member B10 (AKR1B10). The study found 41 active ingredients and 843 targets for the Xihuang Pill. The PPI network included 10 hub genes, including cyclin dependent kinase 1 (CDK1), cyclin B1 (CCNB1), cyclin B2 (CCNB2), polo-like kinase 1 (PLK1), aurora kinase B (AURKB), baculoviral IAP repeat containing 5 (BIRC5), cyclin A2 (CCNA2), aurora kinase A (AURKA), centrosome-associated protein E (CENPE), and threonine tyrosine kinase (TTK), which were the principal target genes at the core of the gene-pathway network for the drug compound to central-target relationship. The enrichment analyses used the overlapping genes and the 10 hub genes and found 390 biological processes (BPs), 25 molecular functions (MFs), 43 cellular components (CCs), and 10 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The main enrichment occurred in the regulation of protein serine-threonine kinase activity, mitotic nuclear division, progesterone-mediated oocyte maturation, and the cell cycle. Conclusions: The study found the targets and relevant pathways of the hub genes of Xihuang Pill using biological analysis and molecular docking and demonstrated the interactions of critical chemical compounds with the hub's targeted genes were. More research is necessary to further determine whether the Xihuang Pill can improve LUSC patients' survival rate by regulation of those genes.

Optical curvature sensor with high resolution based on in-line fiber Mach-Zehnder interferometer and microwave photonic filter.

Curvature measurement plays an important role in structural health monitoring, robot-pose measuring, etc. High-resolution curvature measurement is highly demanded. In this paper, an optical curvature sensor with high resolution based on in-fiber Mach-Zehnder interferometer (MZI) and microwave photonic filter (MPF) is proposed and experimentally demonstrated. The in-fiber MZI is constructed with a ring-core fiber (RCF) which is fusion spliced between two coreless fibers (CLFs). The structure of CLF-RCF-CLF is then sandwiched between two segments of single-mode fiber (SMF), making the whole interferometer structure of SMF-CLF-RCF-CLF-SMF. The operating principle is that different curvatures will cause the variations of the interference spectrum of MZI due to elastic-optic effect, and then the variations are converted into the frequency-shift of the MPF. The factors affecting the visibility of the interference spectrum are researched. A preliminary exploration of the multiplexing demodulation for the in-fiber-MZIs is also investigated and discussed, which is for the first time to the best of our knowledge, holding great potential to pave the way for constructing the sensing network composed of interferometric sensors. The curvature measurement sensitivity is -147.634 MHz/m-1, and the resolution is 6.774 × 10-6 m-1 which is the highest value up to now.

Quantitative demodulation of distributed low-frequency vibration based on phase-shifted dual-pulse phase-sensitive OTDR with direct detection.

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) has been proposed for distributed vibration sensing purpose over recent years. Emerging applications, including seismic and hydroacoustic wave detection, demand accurate low-frequency vibration reconstruction capability. We propose to use the direct-detection Φ-OTDR configuration to achieve quantitative demodulation of external low-frequency vibrations by phase-shifted dual-pulse probes. Simultaneous pulsing and phase shifting modulation is realized with a single acousto-optic modulator to generate such probes, relaxing the need for an additional optical phase modulator. In the experiments, vibrations with frequency as low as 0.5 Hz are successfully reconstructed with 10 m spatial resolution and 35 dB signal-to-noise ratio. Excellent linearity and repeatability are demonstrated between the optical phase demodulation results and the applied vibration amplitudes. The proposed method is capable of quantitative demodulation of low-frequency vibrations with a cost-effective system configuration and high computation efficiency, showing potential for commercial applications of distributed seismic or hydroacoustic wave acquisition.

Ultra-low sampling resolution technique for heterodyne phase-OTDR based distributed acoustic sensing.

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) based on heterodyne detection is widely used for its simple structure and high signal-to-noise ratio (SNR). However, the large amount of raw data of Φ-OTDR places a heavy burden on the storage device and also limits the transferability of the data. In this Letter, we propose an ultra-low sampling resolution technique to solve the data storage problem in heterodyne Φ-OTDR. Experimental results show that the optical phase variations induced by external vibrations can be successfully demodulated from the 1-bit-resolution raw data, and a vibration SNR of 58.03 dB is achieved. In addition, this work also reveals that a data acquisition device with extremely low sampling resolution is sufficient for heterodyne Φ-OTDR, signifying that the cost of the system can be further decreased.

Taohong Siwu decoction promotes the process of fracture healing by activating the VEGF-FAK signal pathway and systemically regulating the gut microbiota.

AIMS: This study aimed to explore the effect of Taohong Siwu Decoction (THSWD) on bone marrow mesenchymal stem cells (BMSCs) at the cellular level and the possible mechanism of systemic regulation of gut microbiota on fracture recovery. METHODS AND RESULTS: Cell Counting Kit-8 (CCK-8) experiments show that THSWD effectively promotes the proliferation of BMSCs. Transwell and wound healing assays show that THSWD effectively promotes the invasion and migration of BMSCs. Alizarin red staining showed that the THSWD model enhanced the osteogenic differentiation of BMSCs. Moreover, the effect of THSWD on BMSCs is time- and concentration-dependent. RT-qPCR and western blot results showed that THSWD treatment up-regulated the expression of vascular endothelial growth factor (VEGF) and focal adhesion kinase (FAK) at mRNA and protein levels, respectively. Haematoxylin-eosin and crocin O-quick green staining showed that after 14 days of THSWD treatment, the area of callus and cartilage regeneration at the fracture site increased significantly in rats with right femoral shaft fractures. Gut microbiota was changed in fractured rats, such as the abundance of Bacteroidetes and Firmicutes was increased. THSWD showed positive regulation of both to a certain extent. CONCLUSION: THSWD up-regulates VEGF and activates the FAK signalling pathway to enhance the development and differentiation of BMSCs, and systematically regulates the gut microbiota to promote fracture healing. SIGNIFICANCE AND IMPACT OF STUDY: This study provides new insights on the cellular and systemic level to understand the mechanism of THSWD in the treatment of fractures.

Data Reduction in Phase-Sensitive OTDR with Ultra-Low Sampling Resolution and Undersampling Techniques.

Data storage is a problem that cannot be ignored in the long-term monitoring of a phase-sensitive optical time-domain reflectometry (Φ-OTDR) system. In this paper, we proposed a data-reduction approach for heterodyne Φ-OTDR using an ultra-low sampling resolution and undersampling techniques. The operation principles were demonstrated and experiments with different sensing configurations were carried out to verify the proposed method. The results showed that the vibration signal could be accurately reconstructed from the undersampled 1-bit data. A space saving ratio of 98.75% was achieved by converting 128 MB of data (corresponding to 268.44 ms of sensing time) to 1.6 MB. The proposed method led to a potentially new data-reduction approach for heterodyne Φ-OTDR, which also provided economical guidance for the selection of the data-acquisition device.

Real-Time Multi-Class Disturbance Detection for Φ-OTDR Based on YOLO Algorithm.

This paper proposes a real-time multi-class disturbance detection algorithm based on YOLO for distributed fiber vibration sensing. The algorithm achieves real-time detection of event location and classification on external intrusions sensed by distributed optical fiber sensing system (DOFS) based on phase-sensitive optical time-domain reflectometry (Φ-OTDR). We conducted data collection under perimeter security scenarios and acquired five types of events with a total of 5787 samples. The data is used as a spatial-temporal sensing image in the training of our proposed YOLO-based model (You Only Look Once-based method). Our scheme uses the Darknet53 network to simplify the traditional two-step object detection into a one-step process, using one network structure for both event localization and classification, thus improving the detection speed to achieve real-time operation. Compared with the traditional Fast-RCNN (Fast Region-CNN) and Faster-RCNN (Faster Region-CNN) algorithms, our scheme can achieve 22.83 frames per second (FPS) while maintaining high accuracy (96.14%), which is 44.90 times faster than Fast-RCNN and 3.79 times faster than Faster-RCNN. It achieves real-time operation for locating and classifying intrusion events with continuously recorded sensing data. Experimental results have demonstrated that this scheme provides a solution to real-time, multi-class external intrusion events detection and classification for the Φ-OTDR-based DOFS in practical applications.

A Growing Link between Circadian Rhythms, Type 2 Diabetes Mellitus and Alzheimer's Disease.

Type 2 diabetes mellitus (T2DM) patients are at a higher risk of developing Alzheimer's disease (AD). Mounting evidence suggests the emerging important role of circadian rhythms in many diseases. Circadian rhythm disruption is considered to contribute to both T2DM and AD. Here, we review the relationship among circadian rhythm disruption, T2DM and AD, and suggest that the occurrence and progression of T2DM and AD may in part be associated with circadian disruption. Then, we summarize the promising therapeutic strategies targeting circadian dysfunction for T2DM and AD, including pharmacological treatment such as melatonin, orexin, and circadian molecules, as well as non-pharmacological treatments like light therapy, feeding behavior, and exercise.

Assessing Heavy Metal Pollution of the Largest Nature Reserve in Tianjin City, China.

Beidagang Wetland (BW) Nature Reserve is centrally situated in Tianjin City, experiencing an extreme industrial development. This study uses index characteristic analysis systems for assessing the individual and combined heavy metal pollution loading in the water during the spring and autumn seasons. By combining the pollution level of single pollutant, a more comprehensive evaluation of water quality in BW was achieved. Water quality was worst during autumn due to high level of Cd and Pb, which indicate the type of anthropogenic activities have a serious effect on heavy metal pollution in BW. In addition, high exchangeable amounts of Cd (> 40%) were found in the sediments of BW, indicating Cd pollution has emerged. There is a need for appropriate abatement actions curbing heavy metal loading and improving water quality of the BW Nature Reserve, thereby ensuring a sustainable management of its ecosystem services.

Clinical relevance of serum immunoglobulin G4 in glucocorticoid therapy of Graves' ophthalmopathy.

OBJECTIVE: Previous study suggested IgG4 levels were associated with the development of Graves' ophthalmopathy (GO). The aims of the present study were to investigate the role of IgG4 levels in glucocorticoid (GC) treatment in GO patients. DESIGN: 69 GO patients were enrolled. Serum thyroid hormones, thyroid antibodies, IgG, IgG4, ophthalmological examinations and orbital MRI were performed. Furthermore, the clinical outcomes (a composite response endpoint including the clinical activity score (CAS), proptosis, vision, intraocular pressure, diplopia and lid width) after high-dose intravenous GC treatment in 32 active moderate-to-severe GO patients were compared. PATIENTS: 69 consecutive patients with GO were asked to participate in the study. 32 of 69 GO patients were treated with high-dose intravenous GCs. MEASUREMENTS: Measurement of serum IgG and IgG4, serum thyroid hormones and thyroid autoantibodies. An overall ophthalmic assessment was performed pretherapy (week 0) and post-therapy (week 12). RESULTS: 33.3% of GO patients (23/69) had elevated IgG4 levels. IgG4 levels were positively correlated with the severity and activity of GO. After GC therapy, IgG4, IgG4/IgG, vision and CAS were significantly improved in GO patients. Patients with high IgG4 levels had a significantly reduced extraocular muscle area (EOMs) and better clinical outcomes than patients with normal IgG4 levels. CONCLUSIONS: Our results suggest a possible subgroup of elevated IgG4 GO patients, with more severe ophthalmopathy and better response to GCs treatment compare with normal IgG4 GO patients.

Low-cost compressive sensing imaging based on spectrum-encoded time-stretch structure.

A low-cost compressive sensing imaging (CSI) system based on spectrum-encoded time-stretch (SETS) structure involving cascaded Mach-Zehnder Interferometers (MZIs) for spectral domain random mixing (also known as the optical random pattern generator) is proposed and experimentally demonstrated. A proof-of-principle simulation and experiment is performed. A mode-locked laser with a repetition rate of 50MHz and low-cost cascaded MZIs as the key devices enable fast CSI system. Data compression ratio from 6% to 25% are obtained using proposed CSI based SETS system. The proposed design solves the big data issue in the traditional time-stretch system. It has great potential in fast dynamic phenomena with low-cost and easy-access components.

Synonymous mutation in Growth Regulating Factor 15 of miR396a target sites enhances photosynthetic efficiency and heat tolerance in poplar.

Heat stress damages plant tissues and induces multiple adaptive responses. Complex and spatiotemporally specific interactions among transcription factors (TFs), microRNAs (miRNAs), and their targets play crucial roles in regulating stress responses. To explore these interactions and to identify regulatory networks in perennial woody plants subjected to heat stress, we integrated time-course RNA-seq, small RNA-seq, degradome sequencing, weighted gene correlation network analysis, and multi-gene association approaches in poplar. Results from Populus trichocarpa enabled us to construct a three-layer, highly interwoven regulatory network involving 15 TFs, 45 miRNAs, and 77 photosynthetic genes. Candidate gene association studies in a population of P. tomentosa identified 114 significant associations and 696 epistatic SNP-SNP pairs that were linked to 29 photosynthetic and growth traits (P<0.0001, q<0.05). We also identified miR396a and its target, Growth-Regulating Factor 15 (GRF15) as an important regulatory module in the heat-stress response. Transgenic plants of hybrid poplar (P. alba × P. glandulosa) overexpressing a GRF15 mRNA lacking the miR396a target sites exhibited enhanced heat tolerance and photosynthetic efficiency compared to wild-type plants. Together, our observations demonstrate that GRF15 plays a crucial role in responding to heat stress, and they highlight the power of this new, multifaceted approach for identifying regulatory nodes in plants.