Revealing the Freezing-Induced Alteration in Microplastic Behavior and Its Implication for the Microplastics Released from Seasonal Ice.

Ice can serve as a significant temporary repository and conveyance mechanism for microplastics (MPs). MPs present in the water column can become entrapped within developing ice formations, subsequently being sequestered and transported by ice floes. With changing temperatures, MPs stored in ice can be released back into the environment, while freezing conditions can alter the properties of MPs, ultimately affecting the fate of MPs in the environment. Freezing of MPs in freshwater ice results in the aggregation of MP particles due to physical compression, leading to an increase in particle size once the MPs are released from the ice. The freezing-induced aggregation enhances buoyancy effects, accelerating the settling/rising velocity of MPs in water. Additionally, freezing can lead to enhanced surface wetting alterations, thus improving the dispersion of hydrophobic MPs. The presence of salt in the water can mitigate the effect of freezing on MPs due to the formation of a brine network within the ice structure, which reduces the pressure on MPs entrapped by ice. In cold regions, numerous MPs undergo freezing and thawing, re-entering the water column.

Confirmation of a measurement model for hospital supply chain resilience.

Background: The hospital supply chain has revealed increasing vulnerabilities and disruptions in the wake of the COVID-19 pandemic, threatening the healthcare services and patient safety. The resilience of hospital supply chains has emerged as a paramount concern within the healthcare system. However, there is a lack of systematic research to develop an instrument tailored to the healthcare industry that is both valid and reliable for measuring hospital supply chain resilience. Therefore, this study aims to construct and validate a comprehensive scale for assessing hospital supply chain resilience, based on dynamic capability theory. Methods: This study followed rigorous scale development steps, starting with a literature review and 15 semi-structured interviews to generate initial items. These items were then refined through expert panel feedback and three rounds of Delphi studies. Using data from 387 hospitals in Province S, mainland China, the scale underwent rigorous testing and validation using structural equation modeling. To ensure the most effective model, five alternative models were examined to determine the most suitable parsimonious model. Results: The study produced a 26-item scale that captures five dimensions of resilience in line with dynamic capability theory: anticipation, adaptation, response, recovery, and learning, all showing satisfactory consistency, reliability and validity. Conclusion: The multi-dimensional scale offers hospital managers a valuable tool to identify areas needing attention and improvement, benchmark resilience against their counterparts, and ultimately strengthen their supply chains against unexpected risks.

Heart size variation in anurans from China does not follow the Hesse's rule.

We failed to dissect the associations between relative heart size and geographical gradients (altitude and latitude) and climatic factors (annual temperature, rainfall, and wind speed) across 116 species, which suggests that heart size variation in anurans did not follow the Hesse's rule.

Shape Memory Polyurethane Composite With Fast Response to Near-Infrared Light Based on Tannic Acid-Iron and Dynamic Phenol-Carbamate Network.

Intelligent materials derived from green and renewable bio-based materials garner widespread attention recently. Herein, shape memory polyurethane composite (PUTA/Fe) with fast response to near-infrared (NIR) light is successfully prepared by introducing Fe3+ into the tannic acid-based polyurethane (PUTA) matrix through coordination between Fe3+ and tannic acid. The results show that the excellent NIR light response ability is due to the even distribution of Fe3+ filler with good photo-thermal conversion ability. With the increase of Fe3+ content, the NIR light response shape recovery rate of PUTA/Fe composite films is significantly improved, and the shape recovery time is reduced from over 60 s to 40 s. In addition, the mechanical properties of PUTA/Fe composite film are also improved. Importantly, owing to the dynamic phenol-carbamate network within the polymer matrix, the PUTA/Fe composite film can reshape its permanent shape through topological rearrangement and show its good NIR light response shape memory performance. Therefore, PUTA/Fe composites with high content of bio-based material (TA content of 15.1-19.4%) demonstrate the shape memory characteristics of fast response to NIR light; so, it will have great potential in the application of new intelligent materials including efficient and environmentally friendly smart photothermal responder.

High burden of human papillomavirus infection among men in Guangzhou, South China: Implications for HPV vaccination strategies.

The epidemiological and clinical aspects of Human Papillomavirus (HPV) infection in women have been extensively studied. However, there is a lack of information regarding HPV characteristics in males. In this study, we conducted a retrospective and observational study of 3737 consecutive male individuals attending outpatient clinics of Guangdong Women and Children Hospital from 2012 to 2023 in Guangzhou, South China, to determine the age- and genotype-specific prevalence of HPV in men. The results showed the overall prevalence of HPV among men was 42.15% (1575/3737), with variations ranging from 29.55% to 81.31% across distinct diagnostic populations. Low-risk HPV6 (15.47%), HPV11 (8.94%), and high-risk HPV52 (5.51%) were the most common types. The annual HPV prevalence decreased significantly (Z = -3.882, p < .001), ranging from 31.44% to 52.90%. 28.77% (1075/3737) of men manifested infection with a singular HPV type, predominantly identified as a low-risk type. The age-specific distribution of HPV infections revealed distinctive peaks in the < 25 y age group (47.60%, 208/437) and the 40-44 y age group (44.51%, 154/346). Notably, the positive rate of Chlamydia trachomatis was significantly higher among HPV-positive individuals in comparison to HPV-negatives (16.14% vs. 11.25%, p < .05). Our findings reveal a substantial prevalence of HPV infection among outpatient men in Guangzhou, South China. It is recommended to consider the inclusion of HPV vaccination for adolescent males in national immunization schedules, once an adequate supply of vaccines is accessible.

Advances in the Application of Single-Cell Transcriptomics in Plant Systems and Synthetic Biology.

Plants are complex systems hierarchically organized and composed of various cell types. To understand the molecular underpinnings of complex plant systems, single-cell RNA sequencing (scRNA-seq) has emerged as a powerful tool for revealing high resolution of gene expression patterns at the cellular level and investigating the cell-type heterogeneity. Furthermore, scRNA-seq analysis of plant biosystems has great potential for generating new knowledge to inform plant biosystems design and synthetic biology, which aims to modify plants genetically/epigenetically through genome editing, engineering, or re-writing based on rational design for increasing crop yield and quality, promoting the bioeconomy and enhancing environmental sustainability. In particular, data from scRNA-seq studies can be utilized to facilitate the development of high-precision Build-Design-Test-Learn capabilities for maximizing the targeted performance of engineered plant biosystems while minimizing unintended side effects. To date, scRNA-seq has been demonstrated in a limited number of plant species, including model plants (e.g., Arabidopsis thaliana), agricultural crops (e.g., Oryza sativa), and bioenergy crops (e.g., Populus spp.). It is expected that future technical advancements will reduce the cost of scRNA-seq and consequently accelerate the application of this emerging technology in plants. In this review, we summarize current technical advancements in plant scRNA-seq, including sample preparation, sequencing, and data analysis, to provide guidance on how to choose the appropriate scRNA-seq methods for different types of plant samples. We then highlight various applications of scRNA-seq in both plant systems biology and plant synthetic biology research. Finally, we discuss the challenges and opportunities for the application of scRNA-seq in plants.

Emergence and circulation of enterovirus B species in infants in southern China: A multicenter retrospective analysis.

BACKGROUND: Enteroviruses (EV) are common and can cause severe diseases, particularly in young children. However, the information of EV infection in infants in China is limited due to the vast population size and extensive geographical area of the country. Here, we conducted a retrospective multicenter analysis of available EV data to assess the current epidemiological situation in the infant population in southern China. METHODS: The study enrolled infants with suspected EV infection from 34 hospitals across 12 cities in southern China between 2019 to 2022, and the confirmation of EV was done using RT-PCR and VP1 gene sequencing. RESULTS: Out of 1221 infants enrolled, 330 (27.03%) were confirmed as EV-infected. Of these, 260 (78.79%) were newborns aged 0-28 days. The EV belonged to three species: EV-B (80.61%), EV-A (11.82%), and human rhinovirus (7.58%). Newborns were more susceptible to EV-B than older infants (p < 0.001). Within EV-B, we identified 15 types, with coxsackievirus (CV) B3 (20.91%), echovirus (E) 11 (19.70%), and E18 (16.97%) being the most common. The predominant EV types changed across different years. EV infection in infants followed a seasonal pattern, with a higher incidence from May to August. Furthermore, perinatal mother-to-child EV transmission in 12 mother-newborn pairs were observed. CONCLUSION: Our study is the first to demonstrate the emergence and widespread circulation of EV-B species, mainly CVB3, E11, and E18, in southern China, primarily affecting young infants. This research provides valuable insights for future epidemic assessment, prediction, as well as the elimination of mother-to-child transmission.

Spotlight on the vertical migration of aged microplastics in coastal waters.

Coastal waters are complex and dynamic areas with unique environmental attributes that complicate the vertical migration of microplastics (MPs). The MPs that enter coastal waters from diverse sources, including terrestrial, riverine, oceanic, and shoreline inputs undergo various aging pathways. In this study, the variations in the physiochemical characteristics of MPs undergoing various aging pathways and their vertical migration under dynamic conditions subjected to the effects of different MP characteristics and coastal environmental features were comprehensively explored. Opposite effects of aging on the vertical migration of hydrophobic and hydrophilic MPs were observed, with aging appearing to promote the dispersion of hydrophobic MPs but enhance the vertical migration of hydrophilic ones. The positive role of salinity and the negative role of humic acid (HA) concentrations on MP vertical migration were identified, and the mechanisms driving these effects were analyzed. Notably, intense turbulence not only promoted the floating of positively buoyant MPs but also reversed the migration direction of negatively buoyant MPs from downward to upward. Aging-induced changes in MP characteristics had a limited effect on MP vertical migration. The inherent characteristics of MPs and the surrounding environmental features, however, played major roles in their vertical migration dynamics. ENVIRONMENTAL IMPLICATION: Microplastics (MPs) have emerged as a significant global environmental concern and the coastal zones are the hotspots for MP pollution due to their high population density. This study comprehensively investigated the variations in the physiochemical characteristics of MPs undergoing various aging pathways. Their vertical migration patterns under dynamic conditions subjected to the effects of different MP characteristics and coastal environmental features were revealed. The roles of turbulence and MP density in their migration were identified. The findings of this study have important implications for understanding the transport and determining the ecological risks of MPs in coastal waters.

Prolonged drying impedes the detachment of microplastics in unsaturated substrate: Role of flow regimes.

The detachment of microplastics (MPs) from porous media under different moisture conditions and flow regimes has garnered limited attention within the research community. The present study investigates the detachment of MPs from porous media under wet and dry conditions combined with steady and transient flow. For both the wet and dry conditions, the increase in flow rates is found to decrease the detachment of hydrophobic polyethylene of two sizes and of hydrophilic polymethylmethacrylate. Intermittent flow is found to result in effluent peaks and a higher rate of MP detachment compared to steady flow. The ionic strength of inflow drops in a stepwise manner, leading to abrupt peaks followed by a tail corresponding to the arrival of each ionic strength front. Each step increase in flow rate leads to a steep peak followed by slow release over several pore volumes. Although transient flow facilitates the detachment of MPs, drying significantly impedes the detachment of MPs irrespective of flow regime. Ultraviolet weathering of MPs for 60 days weakens the inhibition effect of drying on hydrophilic polymethylmethacrylate, facilitating their detachment. Furthermore, the release of MPs decreases markedly with an increase in air-drying duration from 0 h to 72 h. Hydrus-1D two-site kinetic models are used to successfully simulate time-dependent processes, implying that drying heightens the energy barrier for MPs to detach. Our analysis confirms the significance of moisture in determining the remobilization of MPs, providing valuable insights concerning the fate of MPs in unsaturated substrate under prolonged drought conditions.

Inhibiting ferroptosis in brain microvascular endothelial cells: A potential strategy to mitigate polystyrene nanoplastics‒induced blood‒brain barrier dysfunction.

Polystyrene nanoplastics (PS-NPs), a group of ubiquitous pollutants, may injure the central nervous system through the blood‒brain barrier (BBB). However, whether exposure to PS-NPs contributes to BBB disruption and the underlying mechanisms are still unclear. In vivo, we found that PS-NPs (25 mg/kg BW) could significantly increase BBB permeability in mice and downregulate the distribution of the tight junction-associated protein zona occludens 1 (ZO-1) in brain microvascular endothelial cells (BMECs). Using an in vitro BBB model, exposure to PS-NPs significantly reduced the transendothelial electrical resistance and altered ZO-1 expression and distribution in a dose-dependent manner. RNA-seq analysis and functional investigations were used to investigate the molecular pathways involved in the response to PS-NPs. The results revealed that the ferroptosis and glutathione metabolism signaling pathways were related to the disruption of the BBB model caused by the PS-NPs. PS-NPs treatment promoted ferroptosis in bEnd.3 cells by inducing disordered glutathione metabolism in addition to Fe2+ and lipid peroxide accumulation, while suppressing ferroptosis with ferrostatin-1 (Fer-1) suppressed ferroptosis-related changes in bEnd.3 cells subjected to PS-NPs. Importantly, Fer-1 alleviated the decrease in ZO-1 expression in bEnd.3 cells and the exacerbation of BBB damage induced by PS-NPs. Collectively, our findings suggest that inhibiting ferroptosis in BMECs may serve as a potential therapeutic target against BBB disruption induced by PS-NPs exposure.

Unveiling the Vertical Migration of Microplastics with Suspended Particulate Matter in the Estuarine Environment: Roles of Salinity, Particle Properties, and Hydrodynamics.

The estuary is an energetic area connecting the inland, river, and ocean. The migration of microplastics (MPs) in this highly complex area is tied to the entire ecosystem. In this study, the effects of cohesive SPM (clay) and noncohesive SPM (sand) on the vertical migration of positively buoyant MPs, polyethylene (PE), and negatively buoyant MPs, polytetrafluoroethylene (PTFE), in the estuarine environment under hydrodynamic disturbances were investigated. The settling of positively buoyant MPs was more reliant on the cohesive SPM compared to the settling of negatively buoyant MPs. Moreover, MPs interacting with the SPM mixture at a clay-to-sand ratio of 1:9 settled more efficiently than those interacting with clay alone. A significant positive correlation was observed between MP settling percentage and the salinity level. MP settling percentage was significantly negatively correlated with fluid shear stress for both types of MPs, meanwhile, negatively buoyant MPs were able to resist greater hydraulic disturbances. In the low-energy mixing state, for both types of MPs, the settling percentage reached about 50% in only 10 min. The resuspension process of MPs under hydrodynamic disturbances was also uncovered. Additionally, the migration and potential sites of MPs were described in the context of prevalent environmental phenomena in estuaries.

An Untethered Soft Crawling Robot Driven by Wireless Power Transfer Technology.

Soft robots based on flexible materials have attracted the attention due to high flexibility and great environmental adaptability. Among the common driving modes, electricity, light, and magnetism have the limitations of wiring, poor penetration capability, and sophisticated equipment, respectively. Here, an emerging wireless driving mode is proposed for the soft crawling robot based on wireless power transfer (WPT) technology. The receiving coil at the robot's tail, as an energy transfer station, receives energy from the transmitting coil and supplies the electrothermal responsiveness to drive the robot's crawling. By regulating the WPT's duration to control the friction between the robot and the ground, bidirectional crawling is realized. Furthermore, the receiving coil is also employed as a sensory organ to equip the robot with localization, ID recognition, and sensing capabilities based on electromagnetic coupling. This work provides an innovative and promising strategy for the design and integration of soft crawling robots, exhibiting great potential in the field of intelligent robots.

Foveal Microstructure and Visual Outcomes after Pars Plana Vitrectomy in Patients with Different Types of Epiretinal Membrane Foveoschisis.

INTRODUCTION: The aim of this study was to evaluate the clinical characteristics and surgical outcomes of the epiretinal membrane foveoschisis (ERM-FS) with different morphological types. METHODS: This retrospective observational study reviewed 44 consecutive ERM-FS patients who underwent ERM surgery. According to the optical coherence tomography images, ERM-FS was classified into three groups: group A, FS crossed the fovea with the foveola elevated; group B, FS located at the foveal edges with a near-normal central foveal point thickness; and group C, FS with undermined foveal edges with a near-normal central foveal point thickness. RESULTS: There were 10 eyes in group A, 20 eyes in group B, and 14 eyes in group C. Preoperatively, eyes in group A had the best best-corrected visual acuity (BCVA), the thickest central foveal point thickness, and the highest ellipsoid zone (EZ) intact rate among the three groups. After surgery, a resolution of foveoschisis was observed in 40.0%, 45.0%, and 50.0% of the eyes in group A, group B, and group C (p = 0.928), respectively. BCVA was significantly improved postoperatively. Although there was no significant difference in BCVA among the three groups at 1 month postoperatively, BCVA of group A was the best at 4 and 10 months. Correlation analysis indicated that the type of ERM-FS, baseline BCVA, central foveal point thickness, and postoperative EZ continuity (all p < 0.05) were important factors for the final BCVA. CONCLUSIONS: The damage to the retinal structure and visual function was milder in group A ERM-FS. Our study emphasized the necessity of OCT-based subtyping in patients with ERM-FS.

Numerical simulation of mechanical properties of epiretinal membrane peeling.

An epiretinal membrane (ERM) is a fibrocellular proliferation on the inner surface of the retina causing blurred and distorted central vision. Surgery is the only effective method for ERM removal. This paper investigated the mechanical properties of ERM peeling using the finite element (FE) method. A FE model of ERM formation on the retina surface was constructed. The failure criterion was applied to the attachment pegs to represent the adhesive force between the ERM and retina. The simulation results were consistent with the experimental data in published research. The maximum peeling force was 4.1 mN at a peeling velocity of 2 mm/s and an angle of 30°. The peeling force was minimum at the peeling angle of 45° and increased with the increase in peeling velocity and Young's modulus of the membrane. The outcome of this paper can improve the safety and efficiency of ERM removal.

Engineering Crassulacean Acid Metabolism in C3 and C4 Plants.

Carbon dioxide (CO2) is a major greenhouse gas contributing to changing climatic conditions, which is a grand challenge affecting the security of food, energy, and environment. Photosynthesis plays the central role in plant-based CO2 reduction. Plants performing CAM (crassulacean acid metabolism) photosynthesis have a much higher water use efficiency than those performing C3 or C4 photosynthesis. Therefore, there is a great potential for engineering CAM in C3 or C4 crops to enhance food/biomass production and carbon sequestration on arid, semiarid, abandoned, or marginal lands. Recent progresses in CAM plant genomics and evolution research, along with new advances in plant biotechnology, have provided a solid foundation for bioengineering to convert C3/C4 plants into CAM plants. Here, we first discuss the potential strategies for CAM engineering based on our current understanding of CAM evolution. Then we describe the technical approaches for engineering CAM in C3 and C4 plants, with a focus on an iterative four-step pipeline: (1) designing gene modules, (2) building the gene modules and transforming them into target plants, (3) testing the engineered plants through an integration of molecular biology, biochemistry, metabolism, and physiological approaches, and (4) learning to inform the next round of CAM engineering. Finally, we discuss the challenges and future opportunities for fully realizing the potential of CAM engineering.

PREDICTIVE FACTORS ASSOCIATED WITH THE VISUAL PROGNOSIS AFTER SURGERY FOR IDIOPATHIC VITREOMACULAR TRACTION.

PURPOSE: To investigate the predictive factors for postsurgical visual prognosis in patients with vitreomacular traction (VMT). METHODS: This retrospective study enrolled 31 eyes from 29 patients who underwent vitrectomy for idiopathic VMT with a follow-up period of ≥3 months. The VMT was divided into three grades based on optical coherence tomography images: Grade 1 denoted partial vitreomacular separation with foveal attachment; Grade 2 exhibited intraretinal cysts or cleft with grade 1 findings; and Grade 3 was Grade 2 plus the subretinal fluid. RESULTS: Three eyes developed a full-thickness macular hole after surgery, all of which were Grade 3 patients. In the rest 28 eyes, the mean postoperative follow-up period was 23.3 ± 25.8 months. The postoperative central foveal thickness ( P = 0.001) and final best-corrected visual acuity (BCVA; P < 0.001) were both significantly improved from baseline. Fifteen eyes (53.8%) gained ≥ two Snellen lines. Multilinear regression analysis showed that the worse the baseline BCVA ( P = 0.004), or the more advanced the VMT grade ( P = 0.049), the worse the final BCVA. Baseline BCVA was negatively associated with the postoperative visual improvement ( P < 0.001). Those Grade 3 patients with baseline Snellen BCVA of ≥20/40 were more likely to achieve a final Snellen BCVA of ≥20/25 ( P = 0.035). CONCLUSION: The VMT grade is an important predictive factor for the postsurgical visual prognosis. Surgical intervention should be performed as early as possible for Grade 3 patients to prevent further disease progression and maximize the postsurgical visual benefit.

Transcription factor DgMYB recruits H3K4me3 methylase to DgPEROXIDASE to enhance chrysanthemum cold tolerance.

Cold affects the growth and development of plants. MYB transcription factors and histone H3K4me3 transferase ARABIDOPSIS TRITHORAXs (ATXs) play important regulatory functions in the process of plant resistance to low-temperature stress. In this study, DgMYB expression was responsive to low temperature, and overexpression of DgMYB led to increased tolerance, whereas the dgmyb mutant resulted in decreased tolerance of Chrysanthemum morifolium (Dendranthema grandiflorum var. Jinba) to cold stresses. Interestingly, we found that only peroxidase (POD) activity differed substantially between wild type (WT), overexpression lines, and the mutant line. A DgATX H3K4me3 methylase that interacts with DgMYB was isolated by further experiments. DgATX expression was also responsive to low temperature. Overexpression of DgATX led to increased tolerance, whereas the dgatx mutant resulted in decreased tolerance of chrysanthemum to cold stresses. Moreover, the dgmyb, dgatx, and dgmyb dgatx double mutants all led to reduced H3K4me3 levels at DgPOD, thus reducing DgPOD expression. Together, our results show that DgMYB interacts with DgATX, allowing DgATX to specifically target DgPOD, altering H3K4me3 levels, increasing DgPOD expression, and thereby reducing the accumulation of reactive oxygen species (ROS) in chrysanthemum.

Preparation and characterization of ι-carrageenan nanocomposite hydrogels with dual anti-HPV and anti-bacterial activities.

Sexually transmitted diseases (STDs) are usually caused by co-infections of bacteria and viruses. However, there is a lack of products that possess both antibacterial and antiviral activities without using chemical drugs. Here, we developed a carrageenan silver nanoparticle composite hydrogel (IC-AgNPs-Gel) based on the antiviral activity of iota carrageenan (IC) and the antibacterial effect of silver nanoparticles (AgNPs) to prevent STDs. IC-AgNPs-Gel showed excellent biocompatibility, hemostasis, antibacterial and antiviral effects. IC-AgNPs-Gel not only effectively prevented S. aureus, E. coli, P. aeruginosa, and C. albicans without using antibiotics, but also significantly inhibited human papilloma virus (HPV)-16 and HPV-6 without using chemotherapy drugs. Moreover, IC-AgNPs-Gel showed the effects of accelerating infected wound healing and reducing inflammation in a rat wound model infected with S. aureus. Therefore, the multifunctional hydrogel shows great potential application prospect in preventing STDs.

Photoreceptor Outer Segment Loss at the Macular Hole Border: Clinical Characteristics and Surgical Prognosis.

INTRODUCTION: During macular hole (MH) formation, the vitreofoveal traction may lead to foveal neural tissue avulsion and consequent photoreceptor loss. However, the clinical significance of the photoreceptor outer segment disruption at the MH border remains unclear. This study aims to investigate the clinical features and surgical outcomes of MHs with photoreceptor outer segment disruption at the MH border. METHODS: This study retrospectively reviewed 86 eyes from 85 patients who underwent vitrectomy combined with internal limiting membrane peeling for idiopathic MHs. Baseline and postoperative best-corrected visual acuity (BCVA) and foveal microstructure on optical coherence tomography images were compared between eyes with smooth and bumpy morphology, the latter of which was defined as those with an uneven and irregular surface with evident lumps and indentations at the MH border. RESULTS: The bumpy morphology was identified in 59 of 86 eyes (68.9%). At baseline, eyes with a bumpy MH morphology had a significantly larger minimum linear diameter (p = 0.043), a longer external limiting membrane defect (p = 0.013), and a worse baseline BCVA (p = 0.017) than those with a smooth morphology. Postoperatively, in a multivariate regression model adjusting preoperative confounding effects, eyes with bumpy borders were associated with a longer ellipsoid zone defect (p = 0.006) and a thinner central fovea (p = 0.002) at 1 month, and a thinner central fovea (p = 0.005) and a worse BCVA (p = 0.015) at 10 months. CONCLUSION: A severe photoreceptor outer segment loss is common at the MH border, which represents a chronic pathogenic process and may be an independent predictor for an incomplete photoreceptor recovery and worse long-term visual outcomes after surgery.

Functional analysis of Salix purpurea genes support roles for ARR17 and GATA15 as master regulators of sex determination.

The Salicaceae family is of growing interest in the study of dioecy in plants because the sex determination region (SDR) has been shown to be highly dynamic, with differing locations and heterogametic systems between species. Without the ability to transform and regenerate Salix in tissue culture, previous studies investigating the mechanisms regulating sex in the genus Salix have been limited to genome resequencing and differential gene expression, which are mostly descriptive in nature, and functional validation of candidate sex determination genes has not yet been conducted. Here, we used Arabidopsis to functionally characterize a suite of previously identified candidate genes involved in sex determination and sex dimorphism in the bioenergy shrub willow Salix purpurea. Six candidate master regulator genes for sex determination were heterologously expressed in Arabidopsis, followed by floral proteome analysis. In addition, 11 transcription factors with predicted roles in mediating sex dimorphism downstream of the SDR were tested using DAP-Seq in both male and female S. purpurea DNA. The results of this study provide further evidence to support models for the roles of ARR17 and GATA15 as master regulator genes of sex determination in S. purpurea, contributing to a regulatory system that is notably different from that of its sister genus Populus. Evidence was also obtained for the roles of two transcription factors, an AP2/ERF family gene and a homeodomain-like transcription factor, in downstream regulation of sex dimorphism.