Transcriptome analyses of Acer Truncatum Bunge seeds to delineate the genes involved in fatty acid metabolism.

BACKGROUND: Acer truncatum Bunge is an economic, ecological, oil, and medicinal tree, and its kernel oil is rich in nervonic acid. It is crucial to explore the transcriptional expression patterns of genes affecting fatty acid synthesis to improve the quality of Acer truncatum oil. RESULTS: This study used the seeds from high fatty acid strain YQC and those from low fatty acid strain Y38 as the test materials. Specifically, we performed a comparative transcriptome analysis of Y38 seeds and YQC to identify differentially expressed genes (DEGs) at two time points (seeds 30 days after the blooming period and 90 days after the blooming period). Compared with YQC_1 (YQC seeds at 30 days after the blooming period), a total of 3,618 DEGs were identified, including 2,333 up-regulated and 1,285 downregulated DEGs in Y38_1 (Y38 seeds at 30 days after blooming period). In the Y38_2 (Y38 seeds at 90 days after the blooming period) versus YQC_2 (YQC seeds at 90 days after the blooming period) comparison group, 9,340 genes were differentially expressed, including 5,422 up-regulated and 3,918 down-regulated genes. The number of DEGs in Y38 compared to YQC was significantly higher in the late stages of seed development. Gene functional enrichment analyses showed that the DEGs were mainly involved in the fatty acid biosynthesis pathway. And two fatty acid synthesis-related genes and seven nervonic acid synthesis-related genes were validated by qRT-PCR. CONCLUSIONS: This study provides a basis for further research on biosynthesizing fatty acids and nervonic acidnervonic acids in A. truncatum seeds.

Integrated analysis of metabolome, transcriptome, and bioclimatic factors of Acer truncatum seeds reveals key candidate genes related to unsaturated fatty acid biosynthesis, and potentially optimal production area.

BACKGROUND: Lipids found in plant seeds are essential for controlling seed dormancy, dispersal, and defenses against biotic and abiotic stress. Additionally, these lipids provide nutrition and energy and are therefore important to the human diet as edible oils. Acer truncatum, which belongs to the Aceaceae family, is widely cultivated around the world for its ornamental value. Further because its seed oil is rich in unsaturated fatty acids (UFAs)- i.e. α-linolenic acid (ALA) and nervonic acid (NA)- and because it has been validated as a new food resource in China, the importance of A. truncatum has greatly risen. However, it remains unknown how UFAs are biosynthesized during the growth season, to what extent environmental factors impact their content, and what areas are potentially optimal for their production. RESULTS: In this study, transcriptome and metabolome of A. truncatum seeds at three representative developmental stages was used to find the accumulation patterns of all major FAs. Cumulatively, 966 metabolites and 87,343 unigenes were detected; the differential expressed unigenes and metabolites were compared between stages as follows: stage 1 vs. 2, stage 1 vs. 3, and stage 2 vs. 3 seeds, respectively. Moreover, 13 fatty acid desaturases (FADs) and 20 ß-ketoacyl-CoA synthases (KCSs) were identified, among which the expression level of FAD3 (Cluster-7222.41455) and KCS20 (Cluster-7222.40643) were consistent with the metabolic results of ALA and NA, respectively. Upon analysis of the geographical origin-affected diversity from 17 various locations, we found significant variation in phenotypes and UFA content. Notably, in this study we found that 7 bioclimatic variables showed considerable influence on FAs contents in A. truncatum seeds oil, suggesting their significance as critical environmental parameters. Ultimately, we developed a model for potentially ecological suitable regions in China. CONCLUSION: This study provides a comprehensive understanding of the relationship between metabolome and transcriptome in A. truncatum at various developmental stages of seeds and a new strategy to enhance seed FA content, especially ALA and NA. This is particularly significant in meeting the increasing demands for high-quality edible oil for human consumption. The study offers a scientific basis for A. truncatum's novel utilization as a woody vegetable oil rather than an ornamental plant, potentially expanding its cultivation worldwide.

Testing plastomes and nuclear ribosomal DNA sequences as the next-generation DNA barcodes for species identification and phylogenetic analysis in Acer.

BACKGROUND: Acer is a taxonomically intractable and speciose genus that contains over 150 species. It is challenging to distinguish Acer species only by morphological method due to their abundant variations. Plastome and nuclear ribosomal DNA (nrDNA) sequences are recommended as powerful next-generation DNA barcodes for species discrimination. However, their efficacies were still poorly studied. The current study will evaluate the application of plastome and nrDNA in species identification and perform phylogenetic analyses for Acer. RESULT: Based on a collection of 83 individuals representing 55 species (c. 55% of Chinese species) from 13 sections, our barcoding analyses demonstrated that plastomes exhibited the highest (90.47%) species discriminatory power among all plastid DNA markers, such as the standard plastid barcodes matK + rbcL + trnH-psbA (61.90%) and ycf1 (76.19%). And the nrDNA (80.95%) revealed higher species resolution than ITS (71.43%). Acer plastomes show abundant interspecific variations, however, species identification failure may be due to the incomplete lineage sorting (ILS) and chloroplast capture resulting from hybridization. We found that the usage of nrDNA contributed to identifying those species that were unidentified by plastomes, implying its capability to some extent to mitigate the impact of hybridization and ILS on species discrimination. However, combining plastome and nrDNA is not recommended given the cytonuclear conflict caused by potential hybridization. Our phylogenetic analysis covering 19 sections (95% sections of Acer) and 128 species (over 80% species of this genus) revealed pervasive inter- and intra-section cytonuclear discordances, hinting that hybridization has played an important role in the evolution of Acer. CONCLUSION: Plastomes and nrDNA can significantly improve the species resolution in Acer. Our phylogenetic analysis uncovered the scope and depth of cytonuclear conflict in Acer, providing important insights into its evolution.

Anthocyanins act as a sugar-buffer and an alternative electron sink in response to starch depletion during leaf senescence: a case study on a typical anthocyanic tree species, Acer japonicum.

We hypothesized that anthocyanins act as a sugar-buffer and an alternative electron sink during leaf senescence to prevent sugar-mediated early senescence and photoinhibition. To elucidate the role of anthocyanin, we monitored seasonal changes in photosynthetic traits, sugar, starch and N contents, pigment composition, and gene expression profiles in leaves exposed to substantially different light conditions within a canopy of an adult fullmoon maple (Acer japonicum) tree. Enhancement of starch amylolysis accompanied by cessation of starch synthesis occurred in the same manner independent of light conditions. Leaf sugar contents increased, but reached upper limits in the late stage of leaf senescence, even though leaf anthocyanins further increased after complete depletion of starch. Sun-exposed leaves maintained higher energy consumption via electron flow than shade-grown leaves during leaf N resorption. Thus, anthocyanins accumulated in sun-exposed leaves might have a regulative role as a sugar-buffer, retarding leaf senescence, and an indirect photoprotective role as an alternative sink for electron consumption to compensate declines in other metabolic processes such as starch and protein synthesis. In this context, anthocyanins may be key substrates protecting both outer-canopy leaves (against photoinhibition) and inner-canopy leaves (via shading by outer-canopy leaves) from high light stress during N resorption.

Urbanization exacerbates climate sensitivity of eastern United States broadleaf trees.

Tree growth is a key mechanism driving carbon sequestration in forest ecosystems. Environmental conditions are important regulators of tree growth that can vary considerably between nearby urban and rural forests. For example, trees growing in cities often experience hotter and drier conditions than their rural counterparts while also being exposed to higher levels of light, pollution, and nutrient inputs. However, the extent to which these intrinsic differences in the growing conditions of trees in urban versus rural forests influence tree growth response to climate is not well known. In this study, we tested for differences in the climate sensitivity of tree growth between urban and rural forests along a latitudinal transect in the eastern United States that included Boston, Massachusetts, New York City, New York, and Baltimore, Maryland. Using dendrochronology analyses of tree cores from 55 white oak trees (Quercus alba), 55 red maple trees (Acer rubrum), and 41 red oak trees (Quercus rubra) we investigated the impacts of heat stress and water stress on the radial growth of individual trees. Across our three-city study, we found that tree growth was more closely correlated with climate stress in the cooler climate cities of Boston and New York than in Baltimore. Furthermore, heat stress was a significant hindrance to tree growth in higher latitudes while the impacts of water stress appeared to be more evenly distributed across latitudes. We also found that the growth of oak trees, but not red maple trees, in the urban sites of Boston and New York City was more adversely impacted by heat stress than their rural counterparts, but we did not see these urban-rural differences in Maryland. Trees provide a wide range of important ecosystem services and increasing tree canopy cover was typically an important component of urban sustainability strategies. In light of our findings that urbanization can influence how tree growth responds to a warming climate, we suggest that municipalities consider these interactions when developing their tree-planting palettes and when estimating the capacity of urban forests to contribute to broader sustainability goals in the future.

Ribosome footprint profiling enables elucidating the systemic regulation of fatty acid accumulation in Acer truncatum.

BACKGROUND: The accumulation of fatty acids in plants covers a wide range of functions in plant physiology and thereby affects adaptations and characteristics of species. As the famous woody oilseed crop, Acer truncatum accumulates unsaturated fatty acids and could serve as the model to understand the regulation and trait formation in oil-accumulation crops. Here, we performed Ribosome footprint profiling combing with a multi-omics strategy towards vital time points during seed development, and finally constructed systematic profiling from transcription to proteomes. Additionally, we characterized the small open reading frames (ORFs) and revealed that the translational efficiencies of focused genes were highly influenced by their sequence features. RESULTS: The comprehensive multi-omics analysis of lipid metabolism was conducted in A. truncatum. We applied the Ribo-seq and RNA-seq techniques, and the analyses of transcriptional and translational profiles of seeds collected at 85 and 115 DAF were compared. Key members of biosynthesis-related structural genes (LACS, FAD2, FAD3, and KCS) were characterized fully. More meaningfully, the regulators (MYB, ABI, bZIP, and Dof) were identified and revealed to affect lipid biosynthesis via post-translational regulations. The translational features results showed that translation efficiency tended to be lower for the genes with a translated uORF than for the genes with a non-translated uORF. They provide new insights into the global mechanisms underlying the developmental regulation of lipid metabolism. CONCLUSIONS: We performed Ribosome footprint profiling combing with a multi-omics strategy in A. truncatum seed development, which provides an example of the use of Ribosome footprint profiling in deciphering the complex regulation network and will be useful for elucidating the metabolism of A. truncatum seed oil and the regulatory mechanisms.

Microemulsions based on Acer truncatum seed oil and its fatty acids: fabrication, rheological property, and stability.

AIMS: To construct the microemulsion delivery system (ME) loading ATSO and NA and study their physicochemical characteristics to enhance their stability and water solubility. METHODS: By plotting ternary phase diagrams, the composition and proportions of the MEs were determined. The physicochemical characteristics and stability of MEs were evaluated by mean diameter, polydispersity index (PDI), pH, electrical conductivity, transmission electron microscopy (TEM), rheological behaviour measurement, and phase inversion temperature (PIT). RESULTS: The MEs was composed with EL-40 as a surfactant and specifically with the addition of ethanol as a cosurfactant in NA-loaded ME. The mean diameters of ATSO-loaded ME and NA-loaded ME were 39.65 ± 0.24 nm and 32.90 ± 2.65 nm, and PDI were 0.49 ± 0.01 and 0.28 ± 0.14, respectively. The TEM confirmed the spherical and smooth morphology of MEs. The rheological results indicated that MEs are dilatant fluids with the advantages of low viscosity, high fluidity, and tolerance to temperature fluctuations. The mean diameter and PDI of MEs showed no significant change after storage at 25 °C for 28 days and centrifugation. CONCLUSION: The prepared microemulsions could expand the application prospects of ATSO and NA products in cosmetics, medicine, foods and other fields.

Development of a method based on ATR-FTIR spectroscopy to detect maple syrup adulterated with added syrups.

BACKGROUND: Food adulteration is a global concern, whether it takes place intentionally or incidentally. In Canada, maple syrup is susceptible to being adulterated with cheaper syrups such as corn, beet, cane syrups, and many more due to its high price and economic importance. RESULTS: In this study, the use of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was investigated to detect maple syrups adulterated with 15 different sugar syrups at different concentration levels. The spectra were collected in the range of 4000-650 cm-1 in the absorbance unit. These spectra were used to build six libraries and three models. A method that is capable of performing a qualitative library search using a similarity search, which is based on the first derivative correlation search algorithm, was developed. This method was further evaluated and proved to be able to capture adulterated and reject non-adulterated maple syrups, belonging to the color grades golden and amber maple syrups, with an accuracy of 93.9% and 92.3%, respectively. However, for the maple syrup belonging to the dark color grade, this method demonstrated low specificity of 33.3%, and for this reason it was only able to adequately detect adulterated samples from the non-adulterated ones with an accuracy of 81.4%. CONCLUSION: This simple and rapid method has strong potential for implementation in different stages of the maple syrup supply chain for early adulteration detection, particularly for golden and amber samples. Further evaluation and improvements are required for the dark color grade. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The metabolic benefits of substituting sucrose for maple syrup are associated with a shift in carbohydrate digestion and gut microbiota composition in high-fat high-sucrose diet-fed mice.

Overconsumption of added sugars is now largely recognized as a major culprit in the global situation of obesity and metabolic disorders. Previous animal studies reported that maple syrup (MS) is less deleterious than refined sugars on glucose metabolism and hepatic health, but the mechanisms remain poorly studied. Beyond its content in sucrose, MS is a natural sweetener containing several bioactive compounds, such as polyphenols and inulin, which are potential gut microbiota modifiers. We aimed to investigate the impact of MS on metabolic health and gut microbiota in male C57Bl/6J mice fed a high-fat high-sucrose (HFHS + S) diet or an isocaloric HFHS diet in which a fraction (10% of the total caloric intake) of the sucrose was substituted by MS (HFHS + MS). Insulin and glucose tolerance tests were performed at 5 and 7 wk into the diet, respectively. The fecal microbiota was analyzed by whole-genome shotgun sequencing. Liver lipids and inflammation were determined, and hepatic gene expression was assessed by transcriptomic analysis. Maple syrup was less deleterious on insulin resistance and decreased liver steatosis compared with mice consuming sucrose. This could be explained by the decreased intestinal α-glucosidase activity, which is involved in carbohydrate digestion and absorption. Metagenomic shotgun sequencing analysis revealed that MS intake increased the abundance of Faecalibaculum rodentium, Romboutsia ilealis, and Lactobacillus johnsonii, which all possess gene clusters involved in carbohydrate metabolism, such as sucrose utilization and butyric acid production. Liver transcriptomic analyses revealed that the cytochrome P450 (Cyp450) epoxygenase pathway was differently modulated between HFHS + S- and HFHS + MS-fed mice. These results show that substituting sucrose for MS alleviated dysmetabolism in diet-induced obese mice, which were associated with decreased carbohydrate digestion and shifting gut microbiota.NEW & NOTEWORTHY The natural sweetener maple syrup has sparked much interest as an alternative to refined sugars. This study aimed to investigate whether the metabolic benefits of substituting sucrose with an equivalent dose of maple syrup could be linked to changes in gut microbiota composition and digestion of carbohydrates in obese mice. We demonstrated that maple syrup is less detrimental than sucrose on metabolic health and possesses a prebiotic-like activity through novel gut microbiota and liver mechanisms.

Mood, Activity Participation, and Leisure Engagement Satisfaction (MAPLES): results from a randomised controlled pilot feasibility trial for low mood in acquired brain injury.

BACKGROUND: Acquired brain injury (ABI) is linked to increased depression risk. Existing therapies for depression in ABI (e.g., cognitive behavioural therapy) have mixed efficacy. Behavioural activation (BA), an intervention that encourages engaging in positively reinforcing activities, shows promise. The primary aims were to assess feasibility, acceptability, and potential efficacy of two 8-week BA groups. METHODS: Adults (≥ 18 years) recruited from local ABI services, charities, and self-referral via social media were randomised to condition. The Activity Planning group (AP; "traditional" BA) trained participants to plan reinforcing activities over 8 weeks. The Activity Engagement group (AE; "experiential" BA) encouraged engagement in positive activities within session only. Both BA groups were compared to an 8-week Waitlist group (WL). The primary outcomes, feasibility and acceptability, were assessed via recruitment, retention, attendance, and qualitative feedback on groups. The secondary outcome, potential efficacy, was assessed via blinded assessments of self-reported activity levels, depression, and anxiety (at pre- and post-intervention and 1 month follow-up) and were compared across trial arms. Data were collected in-person and remotely due to COVID-19. RESULTS: N = 60 participants were randomised to AP (randomised n = 22; total n = 29), AE (randomised n = 22; total n = 28), or re-randomised following WL (total n = 16). Whether in-person or remote, AP and AE were rated as similarly enjoyable and helpful. In exploring efficacy, 58.33% of AP members had clinically meaningful activity level improvements, relative to 50% AE and 38.5% WL. Both AP and AE groups had depression reductions relative to WL, but only AP participants demonstrated anxiety reductions relative to AE and WL. AP participants noted benefits of learning strategies to increase activities and learning from other group members. AE participants valued social discussion and choice in selecting in-session activities. CONCLUSIONS: Both in-person and remote group BA were feasible and acceptable in ABI. Though both traditional and experiential BA may be effective, these may have different mechanisms. TRIAL REGISTRATION: Clinicaltrials.gov, NCT03874650. Protocol version 2.3, May 26 2020.

Improving species delimitation for effective conservation: a case study in the endemic maple-leaf oak (Quercus acerifolia).

Species delimitation is challenging in lineages that exhibit both high plasticity and introgression. This challenge can be compounded by collection biases, which may downweight specimens morphologically intermediate between traditional species. Additionally, mismatch between named species and observable phenotypes can compromise species conservation. We studied the species boundaries of Quercus acerifolia, a tree endemic to Arkansas, U.S. We performed morphometric analyses of leaves and acorns from 527 field and 138 herbarium samples of Q. acerifolia and its close relatives, Q. shumardii and Q. rubra. We employed two novel approaches: sampling ex situ collections to detect phenotypic plasticity caused by environmental variation and comparing random field samples with historical herbarium samples to identify collection biases that might undermine species delimitation. To provide genetic evidence, we also performed molecular analyses on genome-wide SNPs. Quercus acerifolia shows distinctive morphological, ecological, and genomic characteristics, rejecting the hypothesis that Q. acerifolia is a phenotypic variant of Q. shumardii. We found mismatches between traditional taxonomy and phenotypic clusters. We detected underrepresentation of morphological intermediates in herbarium collections, which may bias species discovery and recognition. Rare species conservation requires considering and addressing taxonomic problems related to phenotypic plasticity, mismatch between taxonomy and morphological clusters, and collection biases.

Hydraulic integrity of plant organs during drought stress and recovery in herbaceous and woody plant species.

The relationship between root, stem, and leaf hydraulic status and stomatal conductance during drought (field capacities: 100-25%) and drought recovery was studied in Helianthus annuus and five tree species (Populus×canadensis, Acer saccharum, A. saccharinum, Picea glauca, and Tsuga canadensis). Measurements of stomatal conductance (gs), organ water potential, and vessel embolism were performed and the following was observed: (i) cavitation only occurred in the petioles and not the roots or stems of tree species regardless of drought stress; (ii) in contrast, all H. annuus organs exhibited cavitation to an increasing degree from root to petiole; and (iii) all species initiated stomatal closure before cavitation events occurred or the expected turgor loss point was reached. After rewatering: (i) cavitated vessels in petioles of Acer species recovered whereas those of P. ×canadensis did not and leaves were shed; (ii) in H. annuus, cavitated xylem vessels were refilled in roots and petioles, but not in stems; and (iii) despite refilled embolisms in petioles of some species during drought recovery, gs never returned to pre-drought conditions. Conclusions are drawn with respect to the hydraulic segmentation hypothesis for above- and below-ground organs, and the timeline of embolism occurrence and repair is discussed.

No evidence of age-related decline in propagated Acer pseudoplatanus and Fraxinus excelsior plants.

Although a substantial body of evidence suggests that large and old trees have reduced metabolic levels, the search for the causes behind this observation has proved elusive. The strong coupling between age and size, commonly encountered in the field, precludes the isolation of the potential causes. We used standard propagation techniques (grafting and air-layering) to decouple the effects of size from those of age in affecting leaf structure, biochemistry and physiology of two broadleaved trees, Acer pseudoplatanus (a diffuse-porous species) and Fraxinus excelsior (a ring-porous species). The first year after establishment of the propagated plants, some of the measurements suggested the presence of age-related declines in metabolism, while other measurements either did not show any difference or suggested variability across treatments not associated with either age or size. During the second year after establishment, only one of the measured properties (specific leaf area) continued to show some evidence of an age-mediated decline (although much reduced compared to the field), whereas, for some properties (particularly for F. excelsior), even the opposite trend of age-related increases was apparent. We concluded that (1) our plants suffered from grafting shock during year 1 and they gradually recovered during year 2; (2) the results over 2 years do not support the statement that age directly mediates ageing in either species but instead suggest that size directly mediates ageing processes; and (3) neither shoots nor roots of A. pseudoplatanus showed any evidence of senescence.

Biophysical and molecular characteristics of senescing leaves of two Norway maple varieties differing in anthocyanin content.

Disassembly and degradation of the photosynthetic protein complexes during autumn senescence, a vital step to ensure efficient nutrient relocalization for winter storage, is poorly understood. Concomitantly with the degradation, anthocyanins are often synthesized. However, as to why leaves accumulate red pigments, no consensus exists. One possibility is that anthocyanins protect senescing leaves from excess light. In this study, we investigated the pigment composition, photosynthetic performance, radical production, and degradation of the photosynthetic protein complexes in Norway maple (Acer platanoides) and in its highly pigmented, purple-colored variety (Faassen's black) during autumn senescence, to dissect the possible roles of anthocyanins in photoprotection. Our findings show that senescing Faassen's black was indeed more resistant to Photosystem II (PSII) photoinhibition, presumably due to its high anthocyanin content, than the green maple. However, senescing Faassen's black exhibited low photosynthetic performance, probably due to a poor capacity to repair PSII. Furthermore, an analysis of photosynthetic protein complexes demonstrated that in both maple varieties, the supercomplexes consisting of PSII and its antenna were disassembled first, followed by the degradation of the PSII core, Photosystem I, Cytochrome b6 f, and ATP synthase. Strikingly, the degradation process appeared to proceed faster in Faassen's black, possibly explaining its poor PSII repair capacity. The results suggest that tolerance against PSII photoinhibition may not necessarily translate to a better fitness. Finally, thylakoids isolated from senescing and non-senescing leaves of both maple varieties accumulated very little carbon-centered radicals, suggesting that thylakoids may not be a major source of reactive oxygen species in senescing leaves.

A sensitive LC-MS/MS method for the quantification of the plant toxins hypoglycin A and methylenecyclopropylglycine and their metabolites in cow's milk and urine and application to farm milk samples from Germany.

Hypoglycin A (HGA) and its homologue methylenecyclopropylglycine (MCPrG) are present in ackee and lychee as well as seeds, leaves, and seedlings of some maple (Acer) species. They are toxic to some animal species and humans. The determination of HGA, MCPrG, and their glycine and carnitine metabolites in blood and urine is a useful tool for screening for potential exposure to these toxins. In addition, HGA, MCPrG, and/or their metabolites have been detected in milk. In this work, simple and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methods without derivatization were developed and validated for the quantification of HGA, MCPrG, and their metabolites in cow's milk and urine. An extraction procedure from milk samples has been developed, whereas a dilute-and-shoot approach was implemented for urine samples. For quantification, the MS/MS analysis was performed in multiple reaction monitoring mode. The methods were validated according to the European Union guidelines using blank raw milk and urine as matrices. The limit of quantification presented here for HGA in milk (1.12 µg/L) is noticeably lower than the lowest published limit of detection (9 µg/L). Acceptable values for recovery (89-106% and 85-104% in milk and urine, respectively) and precision (≤ 20%) were obtained for all the quality control levels. The stability of HGA and MCPrG in frozen milk over a period of 40 weeks has been demonstrated. The method was applied to 68 milk samples from 35 commercial dairy farms and showed the absence of any quantifiable amounts of HGA, MCPrG, and their metabolites.

Distinct redox state regulation in the seedling performance of Norway maple and sycamore.

Norway maple and sycamore, two Acer genus species, have an important ecological value and different sensitivity to stressing factors being currently aggravated by climate change. Seedling growth is postulated to be the main barrier for successful plant establishment under the climate change scenarios. Therefore, the differences in redox regulation during the seedling performance of Norway maple and sycamore were investigated. Seeds of the two Acer species exhibited an identical high germination capacity, whereas seedling emergence was higher in sycamores. PCA analyses revealed that there is more diversification in the leaf characteristics than roots. Norway maple displayed a higher chlorophyll content index (CCI) with a similar leaf mass whereas sycamore seedlings exhibited a higher normalized difference vegetation index (NDVI), higher water content, higher root biomass and higher shoot height. Based on NDVI, sycamore seedlings appeared as very healthy plants, whereas Norway maple seedlings displayed a moderate healthy phenotype. Therefore, redox basis of seedling performance was investigated. The total pool of glutathione was four times higher in sycamore leaves than in Norway maple leaves and was reflected in highly reduced half-cell reduction potential of glutathione. Sycamore leaves contained more ascorbate because the content of its reduced form (AsA) was twice as high as in Norway maple. Therefore, the AsA/DHA ratio was balanced in sycamore leaves, reaching 1, and was halved in Norway maple leaves. Nicotinamide adenine dinucleotide phosphate content was twice as high in sycamore leaves than in Norway maples; however, its reduced form (NADPH) was predominant in Norway maple seedlings. Norway maple leaves exhibited the highest anabolic and catabolic redox charge. The higher reduction capacity and the activity of NADPH-dependent reductases in Norway maple leaves possibly resulted in higher CCI, whereas the larger root system contributed to higher NDVI in sycamore. The different methods of controlling redox parameters in Acer seedlings grown at controlled conditions provided here can be useful in understanding how tree species can cope with a changing environment in the future.

Daily timings of sap production in sugar maple in Quebec, Canada.

Global warming is affecting plant phenology, with potential consequences on the dynamics of growth reactivation of sugar maple and the timings of maple syrup production. In this study, we assess the temperatures inducing the daily reactivation or cessation of sap production. We selected 19 sugarbushes across Quebec, Canada, using a tapping method associated with the tubing system, we recorded the daily timings of onset and ending of sap production during winter and spring 2018, and we associated the hourly temperatures at each site. Sap production occurred from mid-February to the end of April, starting on average between 10 and 11 AM, and ending from 6 to 8 PM. We observed a seasonal pattern in the onset and ending of sap production during spring, with the onset showing a greater change than the ending. Onset and ending of sap production occurred mostly under temperatures ranging between -2 and 2 °C. The production of sap in maple is closely related to circadian freeze-thaw cycles and occurs under nighttime and daytime temperatures fluctuating below and above 0 °C. The daily lengthening of the duration of sap production mirrors the changes in the timings of freeze and thaw events and can be explained by the physical properties of the water and the physiological processes occurring during growth reactivation. The ongoing warming will result in earlier and warmer springs, which may anticipate the cycles of freeze and thaw and advance sap production in sugar maple.

Three New Species of Diaporthe Causing Leaf Blight on Acer palmatum in China.

Diaporthe spp. are often reported as plant pathogens, endophytes, and saprobes. In this study, three new species (Diaporthe foliicola, D. monospora, and D. nanjingensis) on Acer palmatum were described and illustrated based on morphological characteristics and phylogenetic analyses. Phylogenetic relationships of the new species were determined by multilocus phylogenetic analyses based on partial sequences of the internal transcribed spacer (ITS) region, translation elongation factor 1-α (TEF), ß-tubulin (TUB), histone H3 (HIS), and calmodulin (CAL) genes. Genealogical concordance phylogenetic species recognition with a pairwise homoplasy index test was used to verify the conclusions of the phylogenetic analyses. All species were illustrated and their morphology and phylogenetic relationships with other related Diaporthe spp. are discussed. In addition, the tests of Koch's postulates showed that the three new species were pathogens causing leaf blight on A. palmatum.

Identification and Analysis of the CBF Gene Family in Three Species of Acer under Cold Stress.

The C-Repeat Binding Factor (CBF) gene family has been identified and characterized in multiple plant species, and it plays a crucial role in responding to low temperatures. Presently, only a few studies on tree species demonstrate the mechanisms and potential functions of CBFs associated with cold resistance, while our study is a novel report on the multi-aspect differences of CBFs among three tree species, compared to previous studies. In this study, genome-wide identification and analysis of the CBF gene family in Acer truncatum, Acer pseudosieboldianum, and Acer yangbiense were performed. The results revealed that 16 CBF genes (five ApseCBFs, four AcyanCBFs, and seven AtruCBFs) were unevenly distributed across the chromosomes, and most CBF genes were mapped on chromosome 2 (Chr2) and chromosome 11 (Chr11). The analysis of phylogenetic relationships, gene structure, and conserved motif showed that 16 CBF genes could be clustered into three subgroups; they all contained Motif 1 and Motif 5, and most of them only spanned one exon. The cis-acting elements analysis showed that some CBF genes might be involved in hormone and abiotic stress responsiveness. In addition, CBF genes exhibited tissue expression specificity. High expressions of ApseCBF1, ApseCBF3, AtruCBF1, AtruCBF4, AtruCBF6, AtruCBF7, and ApseCBF3, ApseCBF4, ApseCBF5 were detected on exposure to low temperature for 3 h and 24 h. Low expressions of AtruCBF2, AtruCBF6, AtruCBF7 were detected under cold stress for 24 h, and AtruCBF3 and AtruCBF5 were always down-regulated under cold conditions. Taken together, comprehensive analysis will enhance our understanding of the potential functions of the CBF genes on cold resistance, thereby providing a reference for the introduction of Acer species in our country.

Effect of Exogenous Plant Growth Regulators and Rejuvenation Measures on the Endogenous Hormone and Enzyme Activity Responses of Acer mono Maxim in Cuttage Rooting.

The cuttage rooting method for Acer species is difficult to achieve a good efficacy as trees maintain good characteristics at the rejuvenation stage, thus improving the rooting of Acer species. The addition of exogenous hormones and rejuvenation can improve the rooting effect of cuttings; however, the specific regulatory mechanism is still unclear. Here, Acer mono Maxim rejuvenation and non-rejuvenation cuttings were used as test subjects, to investigate the effects of exogenous hormones on the activities of endogenous hormones and antioxidant enzymes in the rooting process of young cuttings. The results showed that exogenous growth-regulating substances significantly improved the rooting rate of A. mono. Exogenous hormones naphthylacetic acid (NAA) + indolebutyric acid (IBA) increased the initial levels of the endogenous hormones, indoleacetic acid (IAA) and abscisic acid (ABA), and the enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO). Rejuvenation treatment prolonged the time of increase in ABA content and indoleacetic acid oxidase (IAAO) activity at the root primordium induction stage, while increasing trans-zeatin riboside (ZR) content and decreasing POD enzyme activity in cuttings. These results demonstrate that A. mono cuttings can achieve the purpose of improving the rooting rate by adding the exogenous hormone (NAA + IBA), which is closely related to the changes of endogenous hormone content and enzyme activity, and these changes of A. mono rejuvenation cuttings are different from non-rejuvenation cuttings.