Dormant Period Research Articles

Phenolic compounds and spare carbohydrates content dynamics in seeds of the invasive species Acer negundo and the native species Acer tataricum in connection with their competitiveness in biocenoses

Changes in the content of various phenolic carboxylic acids (FCC) – chlorogenic (HC), caffeic (CC), ferulic (FC), as well as the amounts of flavonoids and spare carbohydrates (monosaccharides, polysaccharides and starch) in the tissues of Acer tataricum and Acer negundo seed embryos (indigenous and invasive species, respectively) during their storage were studied from October to March (cold chamber, t° = +5°C, humidity 80%). There was a significant increase in the content of HC and the absence of CC in December-January in an aboriginal species with a long dormant period. In the invasive species A. negundo, which does not have a rest period, the level of HC also increased, but was ten times lower than in A. tataricum, while a high level of CC was identified. In terms of flavonoid content, the native species A. tataricum is ten times superior to the invasive A. negundo. The carbohydrate content in A. tataricum was about 40%, and in the tissues of A. negundo seed embryos about 15% and did not change during the entire storage period. The dynamics of the content of phenolic compounds and forms of spare carbohydrates, their relationship with the activation of metabolic processes and protective anti-stress mechanisms during the cold storage of seeds and competitiveness in biocenoses are discussed.

Application of Ethephon Manually or via Drone Enforces Bud Dormancy and Enhances Flowering Response to Chilling in Litchi (Litchi chinensis Sonn.)

Ethephon (2-chloroethylphosphonic acid) is frequently used for flush management in order to maximize flowering in litchi. However, the optimal dosage of ethephon, which balances between flush control effect and the detrimental effect on leaves, is unknown. This study aimed to identify the optimal ethephon dosage and test more efficient ethephon application methods, using a drone for flush control and flowering promotion in litchi. The effects of a single manual full-tree spray of 250, 500 or 1000 mg/L of ethephon in early November on the bud break rate, leaf drop rate, net photosynthetic rate, LcFT1 expression and floral induction (panicle emergence rate and panicle number) in ‘Jingganghongnuo’ litchi were examined in the season of 2021–2022. In the season of 2022–2023, the effects of drone application of 1000 mg/L of ethephon in early November on bud growth and floral induction were observed. The results showed that the manual ethephon treatments were effective at enforcing bud dormancy and elongating the dormancy period and that the effects were positively dependent on dosage. One manual spray of 1000 mg/L of ethephon in late autumn enabled a dormancy period of 6 weeks. The treatments advanced seasonal abscission of old leaves in winter and caused short-term suppression on photosynthesis within 2 weeks after treatment. Ethephon treatments, especially at 1000 mg/L, enhanced the expression of LcFT1 in the mature leaves and promoted floral induction reflected by earlier panicle emergence and increased panicle emergence rate and number in the terminal shoot. The floral promotion effect was also positively dosage dependent. The cumulative chilling hours below 15 °C from the date of treatment to the occurrence of a 20% panicle emergence rate were lowered in ethephon treatments. A drone spray of 1000 mg/L of ethephon solution consumed a sixth of the manual spray solution volume and was two thirds less effective in suppressing bud break compared with manual spraying. However, it achieved a significant flowering promotion effect comparable to traditional manual spraying. The results suggest that ethephon application enhanced flowering responsiveness to chilling as well as enforced bud dormancy. The application of ethephon with a drone proved to be an efficient method for flush control and flower promotion.

TGF-β induces an atypical EMT to evade immune mechanosurveillance in lung adenocarcinoma dormant metastasis.

The heterogeneity of epithelial-to-mesenchymal transition (EMT) programs is manifest in the diverse EMT-like phenotypes occurring during tumor progression. However, little is known about the mechanistic basis and functional role of specific forms of EMT in cancer. Here we address this question in lung adenocarcinoma (LUAD) cells that enter a dormancy period in response to TGF-β upon disseminating to distant sites. LUAD cells with the capacity to enter dormancy are characterized by expression of SOX2 and NKX2-1 primitive progenitor markers. In these cells, TGF-β induces growth inhibition accompanied by a full EMT response that subsequently transitions into an atypical mesenchymal state of round morphology and lacking actin stress fibers. TGF-β induces this transition by driving the expression of the actin-depolymerizing factor gelsolin, which changes a migratory, stress fiber-rich mesenchymal phenotype into a cortical actin-rich, spheroidal state. This transition lowers the biomechanical stiffness of metastatic progenitors, protecting them from killing by mechanosensitive cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Inhibiting this actin depolymerization process clears tissues of dormant metastatic cells. Thus, LUAD primitive progenitors undergo an atypical EMT as part of a strategy to evade immune-mediated elimination during dormancy. Our results provide a mechanistic basis and functional role of this atypical EMT response of LUAD metastatic progenitors and further illuminate the role of TGF-β as a crucial driver of immune evasive metastatic dormancy.

Investigation of Rooting Performance of Some Grapevine Rootstocks with Aeroponic Method

In the study, the aeroponic system examined the rooting performances of three grapevine rootstocks (110R, 1103 Paulsen, 5BB) commonly used in Türkiye. IBA was applied to grapevine cuttings to encourage rooting. Grapevine cuttings taken during the winter dormancy period were placed in the aeroponic system after the necessary pretreatments. Significant improvements were observed in root length, root number, and rooting rate during the rooting process of cuttings placed in the aeroponic system. No diseases or pests were observed during the rooting period in the daily checks. As a result of the study, the highest root length was 17.77 cm in 110R rootstock, while the lowest was 7.1 cm in 1103P rootstock. The highest rooting rate was 76.67% in a 25 ppm IBA application in 1103P rootstock and 73.33% in a 100 ppm IBA application. The lowest rooting was 10% in 110R rootstock at 100 ppm IBA application dose and in the control group. The study's results revealed the positive effects of aeroponic systems in increasing rooting performance. The advantages offered by these systems are essential in terms of sustainability and efficiency in agriculture. Considering global challenges such as climate change and the reduction of agricultural areas, aeroponic systems are expected to find wider applications in the future.

Cellular resiliency and survival of Neuro-2a cells under extreme stress

Stressors such as hypoxia, hypothermia, and acute toxicity often result in widespread cell death. This study investigated the outcomes of Neuro-2a (N2a; mouse neuroblastoma) cells following a cryogenic storage failure that exposed them to a combination of these stressors over a period of approximately 24-30 hours. Remarkably, a small fraction of the cells survived the event, underwent a period of dormancy, and eventually recovered to a healthy state. To understand the underlying resilience mechanisms, we created a model to replicate the dewar failure event and examined changes in phenotype, transcriptomics, proteomics, and mitochondrial activity of the surviving cells during recovery. We found that the surviving cells initially displayed a stressed morphology with irregular membranes and a clustered apperance. They showed an increased expression of proteins related to DNA repair and chromatin modification pathways as well as heightened mitochondrial function shortly after the stress event. As recovery progressed, the stress-responsive pathways, mitochondrial activity, and growth rates normalized toward that of healthy controls, indicating a return to a stable baseline state. These findings suggest that an initial robust energetic state supports key stress-responsive and repair pathways at the early stages of recovery, facilitating cell survival and resiliency after extreme stress. This work provides valuable insights into cellular resilience mechanisms with potential implications for improving cell preservation and recovery in biomedical applications and developing therapeutic strategies for conditions involving cell damage and stress.

Megafire smoke exposure jeopardizes tree carbohydrate reserves and yield.

The global incidence of megafires is on the rise, leading to extensive areas being shrouded in dense smoke for prolonged periods, spanning days or weeks1. Here, by integrating long-term regional observations of non-structural carbohydrate content in trees across California's Central Valley with spatiotemporal satellite data, we present compelling evidence that dense smoke plumes negatively impact carbohydrate stores in three tree species: Prunus dulcis, Pistacia vera and Juglans regia. Our findings show that the presence of smoke causes a significant decrease in total non-structural carbohydrates, with reductions in the accumulation of both soluble sugar and starch reserves. This decline in carbohydrate levels persists through the trees' dormancy period into the next season's bloom, culminating in a reduced yield. Our results highlight a previously unrecognized wildfire threat that could affect plant health and ecosystem stability in both agricultural and natural environments.

Early-successional species show higher tolerance of drought than late-successional species across Europe.

Climate change is exacerbating forest disturbances through more frequent and more intense droughts and fires, undermining their ability to recover from such disturbances. The response of fast-growing early-successional species to drought is poorly understood, despite their key role in ecological succession and their ability to enhance ecosystem resilience. Here, we compared the growth responses to drought events of three early-successional species (silver birch, black poplar, and Scots pine) with that of one late-successional species (European beech) across their natural distribution ranges in Europe. We used tree-ring widths of 6340 trees from 109 forest sites to establish species-specific tree-ring chronologies. We then used multiple linear regressions to analyze which climatic or growth variables (pre-drought growth and growth during drought) best explained the tree responses to drought. Silver birch, Scots pine, and black poplar showed superior drought tolerance, with a slight, non-significant growth reduction under drought, whereas European beech showed a significant decrease in growth. The variables that influenced growth during and after the drought were species-specific. Annual precipitation and growth variables were key predictors of post-drought growth for Scots pine, black poplar, and European beech. Scots pine and silver birch grew better with increasing latitude, i.e., in Northern Europe than in Central Europe, while European beech and black poplar showed more growth at sites with high precipitation during the vegetation and dormant period, respectively. This study provides insights into the drought tolerance of early-successional species and highlights their ability to promote ecological succession and facilitate the transition to drought-resistant, late-successional forest ecosystems.

Different aspects of biochar addition on semi-dry anaerobic digestion of organic fraction of municipal solid waste in continuous mode

This study investigated the use of biochar, derived from a wood gasifier, in semi-dry anaerobic digestion of organic fraction of municipal solid waste (OFMSW). The experiment was conducted in three phases, without biochar and changing the hydraulic retention time (HRT) from 50 to 15 days until first acidification condition (on pH = 6.5), with biochar at an optimal concentration of 30 g/L in HRT= 20–10 day. Also, countermeasures for the acidified reactor with biochar during the dormancy period were investigated. The results demonstrated that adding biochar led to a rapid recovery of the acidified reactor, improved stability parameters, and removed foaming as a disturbance. Biochar addition (30 g/L) enhanced the organic loading rate (OLR) up to 11 kgVS/m3.day with an HRT of 20 days leading to specific methane production of 383 L/kgVS and a volumetric production increase of biomethane by 85 %. However, at higher OLRs with HRT of 10 days, acidification condition resurfaced leading to homogeneous foaming. Excess adding of biochar did not have significant treatment effects but necessitated a no-feeding period (about 45 days) and gentle stirring with long intervals for stable conditions. Overall, the use of biochar along with the OFMSW biogas plant was demonstrated to enhance production efficiency.

Respon Pertumbuhan Bibit Single Bud Tanaman Aglaonema Varietas Donna Carmen Terhadap Aplikasi Zat Pengatur Tumbuh dan Pupuk Daun

Ornamental plants now become a trend among the public. The hobby of growing ornamental plants causes the demand for ornamental plant is increased day by day, especially the Aglaonema ornamental plant. In general, the propagation of Aglaonema plants is carried out by using separation of tillers and stem cuttings of 4-7 segments. Due to the high demand for Aglaonema plants, a new method of plant propagation is needed, in order to produce more plants in a short time, by using the single bud nursery method. Aglaonema stem cuttings are difficult to do because Aglaonema plants has bud's dormancy period. Dormancy of Aglaonema plant buds is triggered by apical dominance. The way to break bud dormancy on Aglaonema cuttings is using zpt auxin (Rootone-f). In addition, plants also need nutrients to grow, by providing fertilizer. Fertilization for ornamental plants generally uses foliar fertilizer (Gandasil D). This research was conducted using a Randomized Block Design (RBD) which consisted of 2 factors, the first factor zpt auxin (Rootone-f) which consisted of 4 levels (0 ppm, 100 ppm, 200 ppm, 300 ppm), and the second factor was Gandasil D foliar fertilizer which consisted of 3 treatment levels (0 g/l, 1 g/l, 2 g/l) so there are 12 treatment combinations. Each combination was repeated 3 times, thus forming 36 experimental units. The data were analyzed by analysis of variance (ANOVA) to determine the effect of the treatment and those whose effects were significantly different were further tested using the Ducan Multiple Range (DMRT) with a 95% confidence level. The combination of auxin zpt treatment (Rootone-f) with a concentration of 200 ppm and Gandasil D foliar fertilizer with a concentration of 2 g/l showed the best treatment combination on the parameters of observing fresh weight of Aglaonema plants. The concentration of zpt auxin (Rootone-f) 200 ppm gave the highest average value of shoot length, number of leaves, root length, and number of roots of Aglaonema plants. The concentration of Gandasil D 2 g/l foliar fertilizer gave the highest average leaf length and leaf width of Aglaonema plants.

Effect of the Phenological Stage on the Phenolic Composition, and Antioxidant and Antimicrobial Properties of Cirsium vulgare (Savi) Ten. Extracts.

Cirsium vulgare (Savi) Ten. is a plant from the Asteraceae family that is commonly used in traditional medicine. The purpose of this work was to investigate the antioxidant and antimicrobial characteristics of phenolic compounds found in ethanol and dry extracts of C. vulgare leaves, inflorescence, and roots during various phenological stages. Apigenin-7-O-glucoside and chlorogenic acid were identified in practically all C. vulgare extracts. Extracts from leaves collected at the end of the phenological dormancy period and in the first growing year had the highest antioxidant (cupric ion-reducing antioxidant capacity of 12,938 Trolox equivalents/g dry weight) and antimicrobial activity (against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Proteus vulgaris, and Candida albicans) with MIC values of ethanol extract from 16.7 mg/mL to 8.35 mg/mL. These extracts included a high concentration of chlorogenic acid and apigenin-7-O-glucoside. Also, dry extracts from C. vulgare roots and inflorescences showed a higher antimicrobial effect compared to ethanolic extracts with MIC values from 5.57 mg/mL to 3 mg/mL. The study emphasizes the critical role of phenological stages and raw material composition in the accumulation of phenolic compounds and their biological activity in C. vulgare. The findings suggest that extracts from C. vulgare leaves, especially those collected at the end of the phonological dormancy period, are promising candidates for further research into bioactive compounds with potential medicinal applications. The strong antioxidant and antibacterial properties of these extracts highlight their potential for development into natural pharmaceutical products.

Carbon allocation dynamics of Spartina alterniflora in Georgia saltmarsh, USA

We developed a phenology-based growth model(PG model) for Spartina alterniflora that incorporates the effects of light, temperature, and salinity on plant production. The PG model is the first to quantify carbon translocation between both above- and below-ground biomass across three phenological periods: growth, senescence, and dormancy periods. This model, fitted to field data from short, medium, and tall S. alterniflora types, estimates physiological parameters such as mass-specific rates of carbon translocation. Once parameterized, the model is applied in forward mode to predict whole-plant production, growth, respiration, mortality, and translocation. Model results reveals that short forms allocate 82 % of photosynthate to below-ground biomass during the growing season, compared to tall (52 %) and medium (22 %) types. However, tall forms, with extensive above-ground biomass, show the highest absolute carbon translocation to below-ground tissues during growth(ave. 3940 g dry weight m−2) and senescence(ave. 265 g dry weight m−2) period. An average mortality rate of 52 % of net production in the tall form below-ground biomass throughout the year indicates a substantial contribution to organic carbon sequestration within the habitat sediment. Model results also reveal that the carbon translocation from below- to above-ground tissues may not be required for survival during winter in milder climate like Sapelo Island, Georgia.

Current Insights into Weak Seed Dormancy and Pre-Harvest Sprouting in Crop Species.

During the domestication of crops, seed dormancy has been reduced or eliminated to encourage faster and more consistent germination. This alteration makes cultivated crops particularly vulnerable to pre-harvest sprouting, which occurs when mature crops are subjected to adverse environmental conditions, such as excessive rainfall or high humidity. Consequently, some seeds may bypass the normal dormancy period and begin to germinate while still attached to the mother plant before harvest. Grains affected by pre-harvest sprouting are characterized by increased levels of α-amylase activity, resulting in poor processing quality and immediate grain downgrading. In the agriculture industry, pre-harvest sprouting causes annual economic losses exceeding USD 1 billion worldwide. This premature germination is influenced by a complex interplay of genetic, biochemical, and molecular factors closely linked to environmental conditions like rainfall. However, the exact mechanism behind this process is still unclear. Unlike pre-harvest sprouting, vivipary refers to the germination process and the activation of α-amylase during the soft dough stage, when the grains are still immature. Mature seeds with reduced levels of ABA or impaired ABA signaling (weak dormancy) are more susceptible to pre-harvest sprouting. While high seed dormancy can enhance resistance to pre-harvest sprouting, it can lead to undesirable outcomes for most crops, such as non-uniform seedling establishment after sowing. Thus, resistance to pre-harvest sprouting is crucial to ensuring productivity and sustainability and is an agronomically important trait affecting yield and grain quality. On the other hand, seed color is linked to sprouting resistance; however, the genetic relationship between both characteristics remains unresolved. The identification of mitogen-activated protein kinase kinase-3 (MKK3) as the gene responsible for pre-harvest sprouting-1 (Phs-1) represents a significant advancement in our understanding of how sprouting in wheat is controlled at the molecular and genetic levels. In seed maturation, Viviparous-1 (Vp-1) plays a crucial role in managing pre-harvest sprouting by regulating seed maturation and inhibiting germination through the suppression of α-amylase and proteases. Vp-1 is a key player in ABA signaling and is essential for the activation of the seed maturation program. Mutants of Vp-1 exhibit an unpigmented aleurone cell layer and exhibit precocious germination due to decreased sensitivity to ABA. Recent research has also revealed that TaSRO-1 interacts with TaVp-1, contributing to the regulation of seed dormancy and resistance to pre-harvest sprouting in wheat. The goal of this review is to emphasize the latest research on pre-harvest sprouting in crops and to suggest possible directions for future studies.

Protein phosphatase 4 maintains the survival of primordial follicles by regulating autophagy in oocytes

In mammalian ovary, the primordial follicle pool serves as the source of developing follicles and fertilizable ova. To maintain the normal length of female reproductive life, the primordial follicles must have adequate number and be kept in a quiescent state before menopause. However, the molecular mechanisms underlying primordial follicle survival are poorly understood. Here, we provide genetic evidence showing that lacking protein phosphatase 4 (PPP4) in oocytes, a member of PP2A-like subfamily, results in infertility in female mice. A large quantity of primordial follicles has been depleted around the primordial follicle pool formation phase and the ovarian reserve is exhausted at about 7 months old. Further investigation demonstrates that depletion of PPP4 causes the abnormal activation of mTOR, which suppresses autophagy in primordial follicle oocytes. The abnormal primordial follicle oocytes are eventually erased by pregranulosa cells in the manner of lysosome invading. These results show that autophagy prevents primordial follicles over loss and PPP4-mTOR pathway governs autophagy during the primordial follicle formation and dormant period.

The Mutual Effects of Pinching and Promalin® on Root Architecture in Two Boxwood Species

Boxwoods are constantly pinched to shape and form hedges, and Promalin® application is used to boost their shoot yield. Having good root development is crucial for the healthy development of plants; however, the effects of such applications on plant root development have generally been ignored in previous studies. Hence, this study evaluated the effects of applications on the root growth of two boxwood species (Buxus sempervirens L. and Buxus balearica Lam.) during the summer dormancy period. Pinching and Promalin® (0, 1 000, 2 000, and 4 000 ppm) were applied to one-year-old seedlings at three different times. Results showed that pinching had a negative effect on root development in both species and both years. Root development was lower in pinched plants than in control plants, which were not pinched. Promalin® at 2 000 ppm was found to be the most effective application on the root parameter. Root development was also higher in the second year than in the first year, depending on temperature, humidity, and the duration of sunshine. It is recommended to apply 2 000 ppm of Promalin® and not prune B. sempervirens. However, if pinching is to be performed, application of Promalin® will be useful to improve root development. For B. balearica, applying pinching and Promalin® together will help increase root development depending on the application time (in periods when the temperature is high).

Pengaruh Air Kelapa, Ekstrak Bawang Merah dan Ekstrak Rebung Bambu Terhadap Perkecambahan Benih Kopi Robusta (Coffea canephora)

Background: Robusta (Coffea canephora) is one type of coffee widely cultivated in Indonesia and is one of the leading commodities. Coffee seeds include seeds that have a long dormancy period that inhibits the germination process. Breaking dormancy can be done by several methods, one of which is soaking in natural growth regulators. Soaking treatment with natural growth regulators can be combined with soaking time treatment to break dormancy. This study aimed to determine the combination of natural growth regulator treatment and the right soaking time for Robusta coffee seed germination. Methods: This research is a 3-repeat Complete Factorial Randomized Design Experiment with the first factor of natural growth regulators type, which consists of 4 levels, namely: Z0 = control; Z1 = coconut water; Z2 = onion extract and Z3 = bamboo shoots, and the second factor is the length of soaking which consists of 3 levels, namely P1 = 12 hours; P2 = 24 hours and P3 = 36 hours. Results: Natural growth regulators' treatment of shallot extract with 24 hours of soaking time gave the best results on all parameters. Conclusions: Using natural growth regulators from coconut water, shallots, and bamboo shoots with several soaking times affects all parameters observed, both in single and combined administration.

A new perspective on tree growing season determination

AbstractDefining plant development timing through seasonal growth and dormancy phases is a valuable proxy for studying climate change and serves as an annual bioindicator. However, current methods for determining the growing season vary due to species‐specific interpretations and differing understandings of its main drivers. Körner et al. (2023) introduced four non‐interchangeable definitions of growing seasons to clarify this complex issue. While some studies have paired different methods, none have simultaneously applied a full set of methods at the individual tree or species level. Here, I aim to present a new perspective to understanding growing season timing by focusing on all facets of above‐ground tree growth and measurable biological and phenological markers. This approach calls for simultaneous, continuous monitoring during active and dormancy periods on the same trees and across different species at a large spatial scale. The goal is to comprehensively understand each method's errors, temporal lags, and the factors determining each growing season, as defined by Körner et al. (2023, Ecology Letters, 26, 1277). Accurate estimation of growing season timing can reshape our understanding of its environmental drivers, improve terrestrial ecosystem models, assess the impact of climate change on tree growth, determine the biological zero for various species, verify remote sensing indices and forecast species distribution.

Using RNA-Seq Analysis to Select Key Genes Related to Seed Dormancy in ALS-Inhibiting Resistant Descurainia sophia with Pro-197-Thr Mutation.

Flixweed (Descurainia sophia) is a weed that seriously affects wheat fields in China. Over the past 20 years, it has evolved resistance to the herbicide tribenuron-methyl. In the present study, a resistant D. sophia population with a Pro-197-Thr mutation of acetolactate synthetase (ALS) was found to have a resistance index of 457.37 for tribenuron-methyl. Under the same growth conditions, the seeds of resistant (R) and susceptible (S) populations exhibited similar vitality but the germination rates of R seeds were higher than those of S seeds. This result demonstrated that seed dormancy periods were shorter in the R seeds. RNA-Seq transcriptome analysis was then used to choose candidate genes that could regulate seed dormancy pathways in the R population. A total of 504,976,046 clean reads were selected from nine RNA-Seq libraries and assembled into 79,729 unigenes. Among these, 33,476 unigenes were assigned to 51 GO subgroups, and 26,117 unigenes were assigned to 20 KEGG secondary metabolic pathways. Next, 2473 differentially expressed genes (DEGs) were divided into three groups, as follows: G-24 h (germinating seeds) vs. D (dormant seeds); G-48 h (germinated seeds) vs. D; and G-48 h vs. G-24 h. From these 2473 DEGs, 8 were selected as candidate dormancy unigenes for the R population if their expression levels continuously decreased during the seed germination progress and their functional annotations were related to plant seed dormancy. One candidate unigene was annotated as CYP707A2; two unigenes were annotated as the transcription factors TGA4 and TGA2; one unigene was annotated as the cystathionine beta-synthase gene; and four unigenes could not be annotated as any gene listed in the six public databases. However, qRT-PCR-validated results showed that, during the germination of R seeds, the expression of the three candidate unigenes first decreased and then increased, indicating that they may have other growth-regulating functions in R populations. In brief, the dormancy function of the eight candidate dormancy unigenes needs to be further studied.

The pseudoenzyme β-amylase9 from Arabidopsis binds to and enhances the activity of α-amylase3: A possible mechanism to promote stress-induced starch degradation.

Starch accumulation in plant tissues provides an important carbon source at night and for regrowth after periods of dormancy and in times of stress. Both ɑ- and β-amylases (AMYs and BAMs, respectively) catalyze starch hydrolysis, but their functional roles are unclear. Moreover, the presence of catalytically inactive amylases that show starch excess phenotypes when deleted presents an interesting series of questions on how starch degradation is regulated. Plants lacking one of these catalytically inactive β-amylases, BAM9, were shown to have enhanced starch accumulation when combined with mutations in BAM1 and BAM3, the primary starch degrading BAMs in response to stress and at night, respectively. Importantly, BAM9 has been reported to be transcriptionally induced by stress through activation of SnRK1. Using yeast two-hybrid experiments, we identified the plastid-localized AMY3 as a potential interaction partner for BAM9. We found that BAM9 interacted with AMY3 in vitro and that BAM9 enhances AMY3 activity 3-fold. Modeling of the AMY3-BAM9 complex revealed a previously undescribed N-terminal structural feature in AMY3 that we call the alpha-alpha hairpin that could serve as a potential interaction site. Additionally, AMY3 lacking the alpha-alpha hairpin is unaffected by BAM9. Structural analysis of AMY3 showed that it can form a homodimer in solution and that BAM9 appears to replace one of the AMY3 monomers to form a heterodimer. Collectively these data suggest that BAM9 is a pseudoamylase that activates AMY3 in response to cellular stress, possibly facilitating starch degradation to provide an additional energy source for stress recovery.

Identification of key genes involved in lignin and flavonoid accumulation during Tilia tuan seed maturation.

Transcriptomics and phenotypic data analysis identified 24 transcription factors (TFs) that play key roles in regulating the competitive accumulation of lignin and flavonoids. Tilia tuan Szyszyl. (T. tuan) is a timber tree species with important ecological and commercial value. However, its highly lignified pericarp results in a low seed germination rate and a long dormancy period. In addition, it is unknown whether there is an interaction between the biosynthesis of flavonoids and lignin as products of the phenylpropanoid pathway during seed development. To explore the molecular regulatory mechanism of lignin and flavonoid biosynthesis, T. tuan seeds were harvested at five stages (30, 60, 90, 120, and 150 days after pollination) for lignin and flavonoid analyses. The results showed that lignin accumulated rapidly in the early and middle stages (S1, S3, and S4), and rapid accumulation of flavonoids during the early and late stages (S1 and S5). High-throughput RNA sequencing analysis of developing seeds identified 50,553 transcripts, including 223 phenylpropanoid biosynthetic pathway genes involved in lignin accumulation grouped into 3 clusters, and 106 flavonoid biosynthetic pathway genes (FBPGs) grouped into 2 clusters. Subsequent WGCNA and time-ordered gene co-expression network (TO-GCN) analysis revealed that 24 TFs (e.g., TtARF2 and TtWRKY15) were involved in flavonoids and lignin biosynthesis regulation. The transcriptome data were validated by qRT-PCR to analyze the expression profiles of key enzyme-coding genes. This study revealed that there existed a competitive relationship between flavonoid and lignin biosynthesis pathway during the development of T. tuan seeds, that provide a foundation for the further exploration of molecular mechanisms underlying lignin and flavonoid accumulation in T. tuan seeds.

Effects of climate change on seed germination may contribute to habitat homogenization in freshwater forested wetlands

Climate changes in temperate regions are expected to result in warmer, shorter winters in temperate latitudes. These changes may have consequences for germination of plant species that require a period of physiological dormancy. The effect of cold duration on seed germination has been investigated in a number of plant taxa, but has not been well studied in wetland and bottomland forest tree species, an ecosystem that is threatened by habitat homogenization. Our work sought to test the role of changing winter temperatures on seed germination in specialist (Nyssa aquatica and Taxodium distichum) and generalist (Acer rubrum and Liquidambar styraciflua) tree species within forested wetlands throughout the eastern U.S. The experiment was conducted in an environmental chamber in Norfolk, VA, USA. Seeds of T. distichum, N. aquatica, A. rubrum, and L. styraciflua were exposed to each of seven pre-germination cold exposure durations (0, 15, 30, 45, 60, 75, and 90 days) and observed for germination for 30 days. Cold stratification duration positively impacted total percent germination in N. aquatica (p < 0.0001) as well as A. rubrum (p = 0.0008) and T. distichum (p = 0.05). Liquidambar styraciflua seeds exhibited more rapid rates of germination with increasing cold exposure duration and greater percent germination compared to the others regardless of cold stratification duration. Our results provide insight into how community dynamics and biodiversity of wetland and bottomland trees may shift with a changing climate. Further, this work emphasizes the importance of understanding the role of plant functional traits in early life stages in community dynamics and has implications for management practices.