Seed Dormancy Release Research Articles

Soil salinity regulates spatial-temporal heterogeneity of seed germination and seedbank persistence of an annual diaspore-trimorphic halophyte in northern China

Background and aimsSeed heteromorphism is a plant strategy that an individual plant produces two or more distinct types of diaspores, which have diverse morphology, dispersal ability, ecological functions and different effects on plant life history traits. The aim of this study was to test the effects of seasonal soil salinity and burial depth on the dynamics of dormancy/germination and persistence/depletion of buried trimorphic diaspores of a desert annual halophyte Atriplex centralasiatica.MethodsWe investigated the effects of salinity and seasonal fluctuations of temperature on germination, recovery of germination and mortality of types A, B, C diaspores of A. centralasiatica in the laboratory and buried diaspores in situ at four soil salinities and three depths. Diaspores were collected monthly from the seedbank from December 2016 to November 2018, and the number of viable diaspores remaining (not depleted) and their germinability were determined.ResultsNon-dormant type A diaspores were depleted in the low salinity “window” in the first year. Dormant diaspore types B and C germinated to high percentages at 0.3 and 0.1 mol L-1 soil salinity, respectively. High salinity and shallow burial delayed depletion of diaspore types B and C. High salinity delayed depletion time of the three diaspore types and delayed dormancy release of types B and C diaspores from autumn to spring. Soil salinity modified the response of diaspores in the seedbank by delaying seed dormancy release in autum and winter and by providing a low-salt concentration window for germination of non-dormant diaspores in spring and early summer.ConclusionsBuried trimorphic diaspores of annual desert halophyte A. centralasiatica exhibited diverse dormancy/germination behavior in respond to seasonal soil salinity fluctuation. Prolonging persistence of the seedbank and delaying depletion of diaspores under salt stress in situ primarily is due to inhibition of dormancy-break. The differences in dormancy/germination and seed persistence in the soil seedbank may be a bet-hadging strategy adapted to stressful temporal and spatial heterogeneity, and allows A. centralasiatica to persist in the unpredictable cold desert enevironment.

Comparative transcriptome analysis reveals the potential mechanism of GA3-induced dormancy release in Suaeda glauca black seeds.

Suaeda glauca Bunge produces dimorphic seeds on the same plant, with brown seeds displaying non-dormant characteristics and black seeds exhibiting intermediate physiological dormancy traits. Previous studies have shown that black seeds have a very low germination rate under natural conditions, but exogenous GA3 effectively enhanced the germination rate of black seeds. However, the physiological and molecular mechanisms underlying the effects of GA3 on S. glauca black seeds are still unclear. In this study, transcriptomic profiles of seeds at different germination stages with and without GA3 treatment were analyzed and compared, and the TTF, H2O2, O2 -, starch, and soluble sugar contents of the corresponding seed samples were determined. The results indicated that exogenous GA3 treatment significantly increased seed vigor, H2O2, and O2 - contents but decreased starch and soluble sugar contents of S. glauca black seeds during seed dormancy release. RNA-seq results showed that a total of 1136 DEGs were identified in three comparison groups and were involved mainly in plant hormone signal transduction, diterpenoid biosynthesis, flavonoid biosynthesis, phenylpropanoid biosynthesis, and carbohydrate metabolism pathway. Among them, the DEGs related to diterpenoid biosynthesis (SgGA3ox1, SgKAO and SgGA2ox8) and ABA signal transduction (SgPP2Cs) could play important roles during seed dormancy release. Most genes involved in phenylpropanoid biosynthesis were activated under GA3 treatment conditions, especially many SgPER genes encoding peroxidase. In addition, exogenous GA3 treatment also significantly enhanced the expression of genes involved in flavonoid synthesis, which might be beneficial to seed dormancy release. In accordance with the decline in starch and soluble sugar contents, 15 genes involved in carbohydrate metabolism were significantly up-regulated during GA3-induced dormancy release, such as SgBAM, SgHXK2, and SgAGLU, etc. In a word, exogenous GA3 effectively increased the germination rate and seed vigor of S. glauca black seeds by mediating the metabolic process or signal transduction of plant hormones, phenylpropanoid and flavonoid biosynthesis, and carbohydrate metabolism processes. Our results provide novel insights into the transcriptional regulation mechanism of exogenous GA3 on the dormancy release of S. glauca black seeds. The candidate genes identified in this study may be further studied and used to enrich our knowledge of seed dormancy and germination.

Methodological and Physiological Study during Seed Dormancy Release of Symplocos paniculata.

Symplocos paniculata are reported to exhibit seed dormancy, which impedes its cultivation and widespread adoption. In this study, a comprehensive method was established to overcome seed dormancy by subjecting seeds to scarification in 98% H2SO4 for 10 min, followed by 1000 mg·L-1 GA3 soaking for 48 h and stratification at 4 °C for 100 days. The seed germination percentage has increased significantly, to a peak of 42.67%, though the seeds could not germinate timely by NaOH scarification. Additionally, the dynamic changes of key stored substances (proteins, soluble sugars, starches, and fats), associated enzyme activities (amylases, peroxidase, and catalase), and endogenous hormones (abscisic acid, gibberellic acid, and indole-3-acetic acid) in seeds were investigated. The results demonstrated a continuous degradation of starch and fat in S. paniculata seeds, while the levels of protein and soluble sugar exhibited fluctuations, which probably facilitated seed dormancy breaking through energy supply and transformation. The enzymatic activities underwent rapid changes, accompanied by a gradual decrease in ABA content within the seeds with increasing stratification time. Notably, GA3, GA3/ABA, and (GA3 + IAA)/ABA showed significant increases, indicating their positive regulatory roles in seed germination. This study clarified the dormancy mechanism and established an effective method for the release dormancy of S. paniculata seeds.

Transcriptome Analysis of Seed in Dormancy and Dormancy Release State of Epimedium koreanum Nakai

Epimedium koreanum is a perennial herb of the Berberidaceae family, which is a traditional tonic in Chinese medicine. Seed germination of E. koreanum is difficult. Dormancy is an intrinsic factor that affects seed germination. Elucidating the molecular mechanism of seed dormancy and the lifting process of E. koreanum is of great significance for the breeding, conservation, and utilization of E. koreanum. Previous studies have concluded that E. koreanum seed dormancy breakage requires warm-temperature stratification followed by low-temperature stratification treatments. Therefore, we performed transcriptome sequencing using freshly harvested, untreated seeds (NS), seeds that developed a cotyledonary embryo after 90 d of constant-temperature stratification at 15 °C (CS), and seeds that broke dormancy by 90 d of stratification at 15 °C and 60 d of stratification at 5 °C (ND) in order to find the responsive genes and regulatory genes that regulate dormancy. A total of 92,867 genes with differential expression were identified. GO enrichment analysis highlighted redox processes, as well as structural components of the nucleus and ribosomes. KEGG enrichment analysis revealed a significant enrichment of phytohormone signaling pathways, which play a crucial role in seed dormancy release. Additionally, protein–protein interactions (PPIs) were predicted with starch and sucrose metabolic pathways. This study introduces a novel concept for a more profound comprehension of the molecular regulatory mechanism of E. koreanum and lays a theoretical foundation for the screening of E. koreanum candidate genes.

Breaking deep epicotyl physiological dormancy in C hionanthus retusus (Oleaceae) seeds

Given that the cause and the method of dormancy release in Chionanthus retusus seeds are unclear, in this study, C. retusus seeds with a hard endocarp (seed dispersal unit) were used for endocarp permeability determination, germination test after endocarp removal and isolated embryo culture to detect the cause of radicle dormancy. Endosperm removal, cold moist stratification, warm moist stratification and GA3 treatment of rooted seeds were used to detect the cause of epicotyl dormancy. The results indicated that C. retusus seeds have non-deep physiological dormancy and deep epicotyl physiological dormancy, the release of which was closely related to the length of the emerged radicle. Rooted seeds with a radicle length < 3 cm could not be effectively released from epicotyl physiological dormancy by endosperm removal, GA3 soaking or cold/warm stratification treatments, whereas those > 3 cm could be significantly promoted for release from epicotyl physiological dormancy by endosperm removal and cold moist stratification treatments. The highest shoot emergence rate of rooted seeds (radicle length > 3 cm) was achieved after 120 days of cold moisture stratification treatment. These results could improve our understanding of seed dormancy and promote the conservation and use of C. retusus.

Unraveling the role of PlARF2 in regulating deed formancy in Paeonia lactiflora.

PlARF2 can positively regulate the seed dormancy in Paeonia lactiflora Pall. and bind the RY cis-element. Auxin, a significant phytohormone influencing seed dormancy, has been demonstrated to be regulated by auxin response factors (ARFs), key transcriptional modulators in the auxin signaling pathway. However, the role of this class of transcription factors (TFs) in perennials with complex seed dormancy mechanisms remains largely unexplored. Here, we cloned and characterized an ARF gene from Paeonia lactiflora, named PlARF2, which exhibited differential expression levels in the seeds during the process of seed dormancy release. The deduced amino acid sequence of PlARF2 had high homology with those of other plants and contained typical conserved Auxin_resp domain of the ARF family. Phylogenetic analysis revealed that PlARF2 was closely related to VvARF3 in Vitis vinifera. The subcellular localization and transcriptional activation assay showed that PlARF2 is a nuclear protein possessing transcriptional activation activity. The expression levels of dormancy-related genes in transgenic callus indicated that PlARF2 was positively correlated with the contents of PlABI3 and PlDOG1. The germination assay showed that PlARF2 promoted seed dormancy. Moreover, TF Centered Yeast one-hybrid assay (TF-Centered Y1H), electrophoretic mobility shift assay (EMSA) and dual-luciferase reporter assay analysis (Dual-Luciferase) provided evidence that PlARF2 can bind to the 'CATGCATG' motif. Collectively, our findings suggest that PlARF2, as TF, could be involved in the regulation of seed dormancy and may act as a repressor of germination.

The Effect of Heat Shock on Seed Dormancy Release and Germination in Two Rare and Endangered Astragalus L. Species (Fabaceae).

Many Astragalus species exhibit seeds with physical dormancy (PY), but little is known about the ecological context of this dormancy. We focused on A. maritimus and A. verrucosus, two threatened Sardinian endemic species inside the subgenus Trimeniaeus Bunge. Fresh seeds collected from the only two respective known populations were used to investigate the effect of mechanical scarification, heat shock, and water imbibition processes on PY release and germination. PY can be overcome through mechanical scarification of the water-impermeable seed coats, while no dormancy break was detected, nor a subsequent increase in seed germination due to fire-induced heat. This suggests that fire does not trigger dormancy release and seed germination in these species. The seeds tolerate relatively high heat shock temperatures (up to 120 and 100 °C for A. verrucosus and A. maritimus, respectively), but after 120 °C for 10 min, the number of dead seeds increases in both species. These facts suggest the capacity to develop a soil seed bank that can persist after fires and delay germination until the occurrence of optimal conditions. As regards water imbibition, both Astragalus species did not show the typical triphasic pattern, as germination started without further water uptake. This study emphasizes the significance of understanding germination processes and dormancy in threatened species. In fire-prone ecosystems, PY dormancy plays a crucial role in soil seed bank persistence, and it may be selectively influenced by post-fire conditions. Understanding such adaptations provides useful insights into conservation strategies.

The Impact of Magnetic Field and Gibberellin Treatment on the Release of Dormancy and Internal Nutrient Transformation in Tilia miqueliana Maxim. Seeds

The seeds of Tilia miqueliana Maxim. exhibit deep dormancy, which is categorized as combinational dormancy. This study utilized a comprehensive treatment involving magnetic fields, gibberellin (GA3), and cold stratification to promote the release of seed physiological dormancy and enhance germination rates. After being soaked in 98% H2SO4 for 15 min, mature seeds of Tilia were exposed to magnetic field treatments (150 MT, 250 MT) for different durations (25 min, 45 min, 65 min, and 85 min), as well as GA3 solution soaking (concentration: 0 μmol·L−1, 1443 μmol·L−1). Subsequently, cold stratification (0–5 °C) was applied to investigate the effects of these treatments on seed dormancy release and nutrient transformation. The results indicated that the comprehensive treatment involving magnetic field, GA3 solution soaking, and cold stratification effectively released the physiological dormancy of Tilia seeds and improved germination rates. Among the treatments, M150T85G1443 (magnetic field intensity: 150 MT, magnetic field treatment time: 85 min, GA3 soaking concentration: 1433 μmol·L−1) exhibited the most favorable outcome. After 75 days of cold stratification following the comprehensive treatments, the germination rate of M150T85G1443 seeds reached 89%. Additionally, the levels of storage substances such as starches and crude fats within the seeds decreased, while the utilization of soluble sugars and soluble proteins increased. The M150T85G1443 treatment exhibited the highest degree of variation, leading to gradual increases in metabolic activities of the seeds and a transition from dormancy to germination.

Evaluation of techniques to break seed dormancy in Redroot pigweed (Amaranthus retroflexus).

By identifying the factors that initiate seed dormancy release, we can reliably predict whether a seed will remain dormant within or exit the seed bank and become a seedling. With regard to annual weed species, assessing which factors efficiently break seed dormancy is critical for estimating the number of weed seeds that will develop into problematic weeds. To better understand dormancy breaking in Redroot pigweed (Amaranthus retroflexus), dormant seeds were treated with cold stratification (4°C for 30 days), application of gibberellic acid (at 500, 1000, 1500, and 2000 parts per million), ultrasound (for 10, 20, 30, and 40 min), soaking in hot water (90°C for 3, 5, 7, and 10 min), and 98% sulfuric acid (for 1, 2, and 3 min). The results showed that Redroot pigweed seed dormancy was effectively broken by cold stratification, gibberellic acid, and ultrasound. Short treatments with hot water had minimal effect while longer times or treatment with sulfuric acid stopped seed germination. In addition to germination percentage, germination rate, plumule length, radicle length, seedling length, seedling dry weight, and seed vigor index were also measured; similarly, application of gibberellic acid had the most significant effect on these parameters. The results of this study add to our knowledge of what processes effectively or ineffectively break Redroot pigweed seed dormancy and promote growth.

Identification and Analysis of the Expression of microRNAs during the Low-Temperature Dormancy Release of Tulipa thianschanica Seeds

With versatile biological functions, microRNAs (miRNAs) participate in the regulation of post-transcriptional gene expression in plants. Tulipa thianschanica Regel is a key wild tulip resource of the Liliaceae; however, it reproduces poorly under natural conditions, and the spreading and expansion of its population rely on the release of its seeds. In this study, T. thianschanica seeds were subjected to stratification at 4 °C for three different durations: 1 d (physiological dormancy), 20 d (dormancy release), and 40 d (non-dormancy). Nine samples were selected, and miRNA databases were established and annotated. This research revealed information on 34 miRNA families, including 14 newly discovered families and 20 families that were previously known. TpmiRNA167 and TpmiRNA395 were observed to be upregulated. Conversely, TpmiRNA166, which targets the key enzymes involved in antioxidant reactions, was downregulated. Notably, PC-5p-84014 and TpmiRNA159 were found to target TpPYL and TpDELLA, respectively, which influenced the abscisic acid/gibberellin (ABA/GA) ratio. Additionally, TpmiRNA160 and TpmiRNA164 were found to participate in the indole-3-acetic acid signal transduction pathway and interact with ABA, thereby contributing to the release of dormancy. In conclusion, this study provides a comprehensive understanding of the mechanism used to release dormancy in T. thianschanica seeds at the molecular level.

Physiological Mechanisms of Bretschneidera sinensis Hemsl. Seed Dormancy Release and Germination

Bretschneidera sinensis, the sole species of Bretschneidera, belonging to the family Akaniaceae, is a tertiary paleotropical flora. It is considered an endangered species by the International Union for Conservation of Nature (IUCN). It has an important protective and scientific value. The study of its seed dormancy and germination mechanisms contributes to better protection. In this study, the dormancy of fresh mature B. sinensis seeds released via low-temperature wet stratification was studied. In addition, the endogenous phytohormone levels, antioxidant enzyme activity, soluble sugar content, and the key metabolic enzyme activities of seeds at different stratification time nodes were determined. The goal was to analyze the mechanisms of seed dormancy release and germination comprehensively. Results show that low-temperature wet stratification under 5 °C can release seed dormancy effectively. During the seed dormancy release, the seed germination rate was positively correlated with soluble sugar, GA3, and IAA levels, as well as G-6-PDH, SOD, POD, CAT, and APX activity, but it was negatively correlated with MDH activity and ABA content. These imply that dormancy release might be attributed to the degradation of endogenous ABA and the oxidation of reactive oxygen species induced by low-temperature wet stratification. GA3, IAA, and the metabolism of energy substrates may be correlated with the induction and promotion of germination.

Dormancy release of seeds of Podophyllum hexandrum Royle accompanied by changes in phytochemicals and inorganic elements.

Podophyllum hexandrum Royle is an alpine medicinal plant of considerable importance, and its seed dormancy severely inhibits population renewal. Although cold stratification can break dormancy to a certain extent, the migration and accumulation of phytochemicals and inorganic elements in the seeds during dormancy release and their functions remain unclear. Changes in phytochemicals and inorganic elements in different seed parts were analyzed during dormancy. The key differential phytochemicals and inorganic elements were screened and their association with dormancy release and their roles in dormancy release were explored. The results showed that dormancy release may have occurred following the decrease in palmitic acid and linoleic acid content in the seeds and the increase in 2,3-dihydro-3,5-dihydro-6-methyl-4 (h)-pyran-4-one content in the endosperm. Meanwhile, 6-propyltridecane and hexadecane in the seed coat may enhance the water permeability of seeds to speed up germination. Mg may migrate from the seed coat to the endosperm and seed embryos, whereas Co may migrate from the seed embryo to the seed coat. Ca, Mn, Mg, and Co are involved in various physiological metabolic processes, which may facilitate the dormancy release of P. hexandrum seeds. These findings have enhanced our understanding of the mechanisms of dormancy release in P. hexandrum seeds and can serve as a reference for the development of more effective dormancy-breaking techniques for the conservation of this endangered medicinal plant.

Dormancy-break and germination requirements for seeds of the threatened Austral papaya (Carica chilensis)

Seed dormancy is one of the most important adaptive mechanisms in plants, optimizing germination, seedling emergence, and establishment to ensure these processes occur when environmental conditions are favorable for plant survival and growth. Endemic to rocky environments of the southern Atacama Desert, the Austral papaya (Carica chilensis) is the papaya species with the southernmost distribution within the Caricaceae, thriving in the most extreme environmental conditions. This threatened plant exhibits low natural regeneration, primarily attributed to low germination, yet no information regarding seed dormancy release is available. In this study, we investigated the dormancy-break and germination requirements of C. chilensis. We hypothesized that if C. chilensis seeds exhibit physiological dormancy, then seeds with reduced moisture content and those treated with chemicals or growth hormones would exhibit higher germination percentages and faster germination than control seeds akin to other members of Caricacea. Our results confirmed this prediction and revealed that ultra-drying (< 3% moisture content) and treating seeds with sulfuric acid, gibberellic acid, or potassium nitrate are the most effective methods for germinating C. chilensis. Consequently, we suggest using these treatments to propagate this threatened papaya species.

Seed Dormancy Characteristics of Kadsura coccinea (Lem.) A. C. Smith, a Unique Medicinal Plant in Southeast Asia

Kadsura coccinea (Lem.) A. C. Smith is a significant tree species of non-timber forest. However, the low germination percentage and lengthy germination time of its seeds pose obstacles to industry development. Aiming at the problem of seed dormancy, this study first determined the seed dormancy period through seed germination test, and then comprehensively evaluated the dormancy characteristics by observing the seed coat structure, measuring endogenous inhibitors, and in vitro embryo culture. The results indicated the dormancy of K. coccinea seeds, and that the germination period was up to 80 days. Its seed coat is composed of exotesta and endotesta. The dense seed coat structure causes water absorption and air permeability obstacles to the seeds and causes mechanical restraint to the development of the embryo. Meanwhile, its seeds have substances that inhibit seed germination, and there are germination inhibitors in distilled water, methanol, petroleum ether, and ethyl acetate extracts of kernels and seed coats. The inhibitory activity of kernel petroleum ether extract was the highest, and the inhibitory activity of seed coat methanol extract was the highest. In addition, the embryo of K. coccinea developed completely and could germinate normally under in vitro conditions. This study has basically proved that the dormancy of K. coccinea seeds is caused by the seed coat (physical dormancy) and endogenous inhibitors (physiological dormancy), which provides a scientific theoretical basis to further explore the method of seed dormancy release of K. coccinea.

The metagenomics of soil bacteria and fungi and the release of mechanical dormancy in hard seeds.

Persistence in the soil is a function of seed physiology, particularly non-germination and inherent lifespan. However, for seeds with mechanical dormancy, non-germination is also a function of the composition and activity of the soil microbiota. We attempted to screen out microorganisms in the soil that can specifically and rapidly decompose the hard fruit pericarps of Tilia miqueliana Maxim., a unique native tree species in China. Using the classical replica plating method, more than 100 different culturable microorganisms that could rapidly erode the pericarp were collected from the surface of pericarps under different culture conditions. At the same time, we successfully extended the concept of metagenomics and applied it to the identification of mixed artificial cultures. The decomposition process of the pericarps in soil was also simulated artificially. The physical and chemical data suggested a potential mechanism of microbial scarification and cracking in pericarp, whilst the embryos inside the eroded fruits retained good viability. Our discoveries could pave the way for the removal of physical and mechanical obstacles that prevent hard coat seeds from germinating. We anticipate that the use of this technology will improve the germination of other hard coat seeds. More research is needed to investigate the impacts on other seeds. The findings of this research can inform the design of experiments on the seed ecology of persistence.

Methodological and physiological study of seed dormancy release in Tilia henryana

Tilia henryana is a rare tree of the Tilia family, found exclusively in China. Its seeds have severe dormancy features that limit its normal conditions of reproduction and renewal. Its seeds have severe dormant characteristics that limit its normal conditions of reproduction and renewal. The Dormancy in T. henryana seeds is a comprehensive dormancy (PY + PD) caused by mechanical and permeability barriers of seed coat and the presence of germination inhibitor in endosperm. L9 (34) orthogonal test was used to determine the best procedure for releasing the dormancy of T. henryana seeds, that is, first treating the seeds with H2SO4 for 15 min, followed by the application of 1 g L−1 GA3, stratification at 5 °C for 45 days, and finally germination at 20 °C, which can achieve a 98% seed germination rate. Large amounts of fat are consumed throughout the dormancy release process. As quantities of protein and starch marginally increase, soluble sugars are continuously decreased. Acid phosphatase and amylase activities increased rapidly, and the combined enzyme activities of G-6-PDH and 6-PGDH related to the PPP were also significantly increased. The levels of GA and ZR continued to increase, while the levels of ABA and IAA gradually decreased, among which GA and ABA changed most rapidly. The total amino acids content continued to decrease. Asp, Cys, Leu, Phe, His, Lys and Arg decreased with dormancy release, while Ser, Glu, Ala, Ile, Pro and Gaba showed an upward trend. The physical dormancy of T. henryana seeds is broken with H2SO4 in order to make the seed coat more permeable, which is a prerequisite for germination. As a result, the seeds can absorb water and engage in physiological metabolic activities, particularly the hydrolysis and metabolism of fat, which supply a significant amount of energy for dormancy release. In addition, rapid variations in the levels of different endogenous hormones and free amino acids, induced by cold stratification and GA3 application, are another important factor promoting the quick physiological activation of seeds and breaking the endosperm barrier.

Nitric Oxide Regulates Seed Germination by Integrating Multiple Signalling Pathways.

Seed germination is of great significance for plant development and crop yield. Recently, nitric oxide (NO) has been shown to not only serve as an important nitrogen source during seed development but also to participate in a variety of stress responses in plants to high salt, drought, and high temperature. In addition, NO can affect the process of seed germination by integrating multiple signaling pathways. However, due to the instability of NO gas activity, the network mechanism for its fine regulation of seed germination remains unclear. Therefore, this review aims to summarize the complex anabolic processes of NO in plants, to analyze the interaction mechanisms between NO-triggered signaling pathways and different plant hormones such as abscisic acid (ABA) and gibberellic acid (GA), ethylene (ET) and reactive oxygen species (ROS) signaling molecules, and to discuss the physiological responses and molecular mechanisms of seeds during the involvement of NO in abiotic stress, so as to provide a reference for solving the problems of seed dormancy release and improving plant stress tolerance.

Transcriptome and proteome analyses reveal the potential mechanism of seed dormancy release in Amomum tsaoko during warm stratification

BackgroundIn Amomum tsaoko breeding, the low germination rate is the major limitation for their large-scale reproduction. We found that warm stratification was an effective treatment to break the seed dormancy of A. tsaoko prior to sowing and could be an important component of improving breeding programs. The mechanism of seed dormancy release during warm stratification remains unclear. Therefore, we studied the differences between transcripts and proteomes at 0, 30, 60, and 90 days of warm stratification, to identify some regulatory genes and functional proteins that may cause seed dormancy release in A. tsaoko and reveal their regulatory mechanism.ResultsRNA-seq was performed for the seed dormancy release process, and the number of differentially expressed genes (DEGs) was 3196 in three dormancy release periods. Using TMT-labelling quantitative proteome analysis, a total of 1414 proteins were defined as differentially expressed proteins (DEPs). Functional enrichment analyses revealed that the DEGs and DEPs were mainly involved in signal transduction pathways (MAPK signaling, hormone) and metabolism processes (cell wall, storage and energy reserves), suggesting that these differentially expressed genes and proteins are somehow involved in response to seed dormancy release process, including MAPK, PYR/PYL, PP2C, GID1, GH3, ARF, AUX/IAA, TPS, SPS, and SS. In addition, transcription factors ARF, bHLH, bZIP, MYB, SBP, and WRKY showed differential expression during the warm stratification stage, which may relate to dormancy release. Noteworthy, XTH, EXP, HSP and ASPG proteins may be involved in a complex network to regulate cell division and differentiation, chilling response and the seed germination status in A. tsaoko seed during warm stratification.ConclusionOur transcriptomic and proteomic analysis highlighted specific genes and proteins that warrant further study in fully grasping the precise molecular mechanisms that control the seed dormancy and germination of A. tsaoko. A hypothetical model of the genetic regulatory network provides a theoretical basis for overcoming the physiological dormancy in A. tsaoko in the future.

Preliminary identification of the changes of physiological characteristics and transcripts in rice after-ripened seeds

A common way of breaking seed dormancy in cereal crops is by treating seeds with a period of dry storage or after-ripening. In this study, we determined changes in the physiological characteristics and transcripts in after-ripened seeds in rice. Phenotypic data showed that the seed dormancy of five rice varieties was gradually released with after-ripening. Physiological results showed that, at the early stage of after-ripening from the freshly harvested seeds (0 days after-ripening, DAR) to 28 DAR, abscisic acid (ABA) content significantly decreased, hydrogen peroxide (H₂O₂) levels significantly increased, superoxide dismutase (SOD) and α-amylase activities significantly raised, and bioactive gibberellin (GA₁) content and ascorbate peroxidase (APX) activity showed no changes in Nipponbare seeds. RNA-seq showed that the 149 changed transcripts were observed at the early stage of after-ripening. Of these transcripts, transcript levels of <italic>OsOxO1</italic>, <italic>OsNCED4</italic>, <italic>RSOsPR10</italic>, and <italic>OsPR10a</italic> mainly occurred at early stages by the verification of four other rice varieties in after-ripened seeds, perhaps signifying that those transcripts played pivotal roles in rice after-ripening. At the late stage of after-ripening, from 28 to 56 DAR, there were merely changes in transcription and translation. Our results facilitated an understanding of the biological process of after-ripening and dormancy release in rice seeds.

Natural distribution and phenotypic traits of Neltuma flexuosa var. depressa, a candidate taxon for the rehabilitation in the central arid region of Argentina

Dryland rehabilitation in the central arid region of Argentina is urgently needed to reverse the current high levels of degradation. Neltuma flexuosa var. depressa, adapted to arid environments, gives it the potential to be used in rehabilitation, for extensive livestock grazing and apiculture. When the soil seed bank is exhausted and natural regeneration is impossible, seed-based rehabilitation programmes constitute one of the more promising options. Thornless ecotype selection could improve pods utilization, so studies of the population distribution can be useful as a genetic resource for pre-breeding. Niche occupancy exhibits a large latitudinal extension (32–43°S), mainly in areas of salinity. All populations would have a transient soil seed bank, but seed dormancy release was lower in populations originating in more unpredictable environments, which distributes germination across years and acts as a bet-hedging strategy between seasons. We observed differences between the populations, with greater spinescence being associated with higher isothermality and lower annual precipitation (r > 80***) at the population's place of origin, showing local adaptation. We also found some thornless seedlings (1.67%) in a population with lower spinescence. However, the plastic response of thorns in seedlings, as well as later stages, should be evaluated in stressful environments.