Delay In Germination Research Articles

ICE1 and ZOU determine the depth of primary seed dormancy in Arabidopsis independently of their role in endosperm development.

SummarySeed dormancy is a widespread and key adaptive trait that is essential for the establishment of soil seed banks and prevention of pre‐harvest sprouting. Herein we demonstrate that the endosperm‐expressed transcription factors ZHOUPI (ZOU) and INDUCER OF CBF EXPRESSION1 (ICE1) play a role in determining the depth of primary dormancy in Arabidopsis. We show that ice1 or zou increases seed dormancy and the double mutant has an additive phenotype. This increased dormancy is associated with increased ABA levels, and can be separated genetically from any role in endosperm maturation because loss of ABA biosynthesis or DELAY OF GERMINATION 1 reverses the dormancy phenotype without affecting the aberrant seed morphology. Consistent with these results, ice1 endosperms had an increased capacity for preventing embryo greening, a phenotype previously associated with an increase in endospermic ABA levels. Although ice1 changes the expression of many genes, including some in ABA biosynthesis, catabolism and/or signalling, only ABA INSENSITIVE 3 is significantly misregulated in ice1 mutants. We also demonstrate that ICE1 binds to and inhibits expression of ABA INSENSITIVE 3. Our data demonstrate that Arabidopsis ICE1 and ZOU determine the depth of primary dormancy during maturation independently of their effect on endosperm development.

Mitochondrial small heat shock protein mediates seed germination via thermal sensing

Seed germination is an energy demanding process that requires functional mitochondria upon imbibition. However, how mitochondria fine tune seed germination, especially in response to the dynamics of environmental temperature, remains largely unknown at the molecular level. Here, we report a mitochondrial matrix-localized heat shock protein GhHSP24.7, that regulates seed germination in a temperature-dependent manner. Suppression of GhHSP24.7 renders the seed insensitive to temperature changes and delays germination. We show that GhHSP24.7 competes with GhCCMH to bind to the maturation subunit protein GhCcmFc to form cytochrome C/C1 (CytC/C1) in the mitochondrial electron transport chain. GhHSP24.7 modulates CytC/C1 production to induce reactive oxygen species (ROS) generation, which consequently accelerates endosperm rupture and promotes seed germination. Overexpression of GhHSP24.7's homologous genes can accelerate seed germination in Arabidopsis and tomato, indicating its conserved function across plant species. Therefore, HSP24.7 is a critical factor that positively controls seed germination via temperature-dependent ROS generation.

Basalt Milkvetch Responses to Novel Restoration Treatments in the Great Basin

The restoration of native forbs in the Great Basin and similar dryland ecosystems remains a great challenge for land managers. Variable soil water, precocious germination and emergence, and the presence of soil fungal pathogens often reduce plant establishment. Novel restoration treatments that increase soil water during early forb life stages, delay germination and emergence to coincide with favorable spring conditions, and reduce mortality from soil fungal pathogens may benefit native forb restoration. We compared the efficacy of three novel treatments—snow fencing, plant protection fabric, and seed coatings—to improve establishment of a forb species native to the Great Basin, basalt milkvetch (Astragalus filipes Torr. ex A. Gray). We replicated treatments plus a no-treatment control at three sites in the Great Basin in a randomized complete block design over 2 yr. To evaluate the efficacy of our restoration treatments, we measured germination, seedling emergence, establishment, and second-yr survival. The effects of snow fencing and plant protection fabric varied by site and life stage and were likely influenced by the wet spring conditions across sites, particularly the two northern sites. Snow fencing increased establishment and second-yr survival at one site. Plant protection fabric did not benefit any life stage at any site. Seed coatings increased seedling emergence at all sites but did not affect establishment or survival. Overall, second-yr survival remained low across all sites and treatments. Our study indicates that our treatments can positively affect basalt milkvetch emergence, establishment, and survival, but additional management actions are needed to improve long-term restoration success of native forbs.

Overexpression of BdRHP1 improves drought tolerance and reduces yield loss in rice

Drought is a major factor decreasing the growth, development, and productivity of rice in about one-third of the world area. The characterization of genes imparting tolerance to drought in rice, is an attractive strategy for genetic engineering to improve drought tolerance. It is demonstrated that ectopic overexpression of Brachypodium distachyon RING-H2 finger gene (designated as BdRHP1) enhances drought tolerance in rice at both the vegetative and reproductive stages. When subjected to drought, positive transgenic lines showed delayed wilting, and improved recovery after rewatering. However, the transgenic plants exhibited more significant germination delay and shoot and root growth arrest than WT under 5 μM abscisic acid (ABA) treatment. When they were subjected to drought at the reproductive stage, the transgenic plants lost water more slowly compared to WT and they had higher leaf relative water content. After 28 d of slow progressive soil drying, transgenic plants recovered better after rewatering and flowered earlier than WT plants. The yield of water-stressed transgenic plants was higher than that of WT plants. Together, the data suggest that BdRHP1 has a specific function in positive modulation of improving drought tolerance in rice.

Novel loci and a role for nitric oxide for seed dormancy and preharvest sprouting in barley.

Barley is used for food and feed, and brewing. Nondormant seeds are required for malting, but the lack of dormancy can lead to preharvest sprouting (PHS), which is also undesired. Here, we report several new loci that modulate barley seed dormancy and PHS. Using genome-wide association mapping of 184 spring barley genotypes, we identified four new, highly significant associations on chromosomes 1H, 3H, and 5H previously not associated with barley seed dormancy or PHS. A total of 71 responsible genes were found mostly related to flowering time and hormone signalling. A homolog of the well-known Arabidopsis Delay of Germination 1 (DOG1) gene was annotated on the barley chromosome 3H. Unexpectedly, DOG1 appears to play only a minor role in barley seed dormancy. However, the gibberellin oxidase gene HvGA20ox1 contributed to dormancy alleviation, and another seven important loci changed significantly during after-ripening. Furthermore, nitric oxide release correlated negatively with dormancy and shared 27 associations. Origin and growth environment affected seed dormancy and PHS more than did agronomic traits. Days to anthesis and maturity were shorter when seeds were produced under drier conditions, seeds were less dormant, and PHS increased, with a heritability of 0.57-0.80. The results are expected to be useful for crop improvement.

Responses of seed germination and shoot metabolic profiles of maize (Zea mays L.) to Y2O3 nanoparticle stress.

The potential risks of rare-earth nanoparticles (RENPs) to plants in the environment are attracting increasing attention due to their wide-spread application. In this regard, little is known about the effects of Y2O3 NPs as an important member of RENPs on crop plants. Seed germination is vulnerable to environmental stress, which determines the growth and yield of crops. Here, maize seeds were exposed to a Y2O3 NP suspension (0–500 mg L−1) in the dark for 6 days. It was found that the Y2O3 NPs had no significant effect on the germination rates (>93%) in all treatments, but they could reduce seed vitality, delay germination, and inhibit seedling growth in a dose-dependent manner. Further, the inhibition effect of Y2O3 NPs on root elongation was much stronger than that on shoot elongation. Meanwhile, the activities of peroxidase (POD) and catalase (CAT) in shoots were enhanced with the increase in the Y2O3 NP concentration. A high-concentration (≥300 mg L−1) of Y2O3 NPs induced a significant increase in the malondialdehyde (MDA) level in shoots compared to the control, indicating that the membrane lipid peroxidation and permeability were enhanced. 1H NMR-based analysis showed that the polar metabolic profiles were altered significantly after treatment with 0, 10, and 500 mg L−1 of Y2O3 NPs, but there was no marked alteration observed for the non-polar metabolic profiles. The polar metabolites (e.g., sugars, amino acids, and most organic acids) showed a dose-dependent increase to Y2O3 NP stress, indicating that the metabolic pathways of carbohydrate metabolism, the tricarboxylic acid cycle (TCA), and amino acid synthesis were disturbed. There were significantly positive correlations found among the metabolites related with the antioxidant response and osmotic adjustment. The simultaneous accumulation of these metabolites possibly indicated the adaptation of the seedlings to stress at the cost of retarding glycolysis, TCA, and protein synthesis. The retarded effects finally inhibited the apparent growth of the seedlings. These findings reveal the phytotoxicity of Y2O3 NPs and provide physiological and biochemical and molecular-scale perspectives on the response of seedlings to stress.

Phenotyping for Nitrogen Use Efficiency: Rice Genotypes Differ in N-Responsive Germination, Oxygen Consumption, Seed Urease Activities, Root Growth, Crop Duration, and Yield at Low N

The biological improvement of fertilizer nitrogen use efficiency (NUE) is hampered by the poor characterization of the phenotype and genotype for crop N response and NUE. In an attempt to identify phenotypic traits for N-response and NUE in the earliest stages of plant growth, we analyzed the N-responsive germination, respiration, urease activities, and root/shoot growth of 21 Indica genotypes of rice (Oryza sativa var. indica). We found that N delays germination from 0 to 12 h in a genotype-dependent and source-dependent manner, especially with urea and nitrate. We identified contrasting groups of fast germinating genotypes such as Aditya, Nidhi, and Swarnadhan, which were also least delayed by N and slow germinating genotypes such as Panvel 1, Triguna, and Vikramarya, which were also most delayed by N. Oxygen uptake measurements in the seeds of contrasting genotypes revealed that they were affected by N source in accordance with germination rates, especially with urea. Germinating seeds were found to have endogenous urease activity, indicating the need to explore genotypic differences in the effective urea uptake and metabolism, which remain unexplored so far. Urea was found to significantly inhibit early root growth in all genotypes but not shoot growth. Field evaluation of 15 of the above genotypes clearly showed that germination rates, crop duration, and yield are linked to NUE. Slow germinating genotypes had longer crop duration and higher yield even at lower N, indicating their higher NUE, relative to fast germinating or short duration genotypes. Moreover, longer duration genotypes suffered lesser yield losses at reduced N levels as compared to short duration genotypes, which is also a measure of their NUE. Together, these results indicate the potential of germination rates, crop duration, urea utilization and its effect on root growth in the development of novel phenotypic traits for screening genotypes and crop improvement for NUE, at least in rice.

The SCO1731 methyltransferase modulates actinorhodin production and morphological differentiation of Streptomyces coelicolor A3(2)

Streptomyces coelicolor is a Gram-positive microorganism often used as a model of physiological and morphological differentiation in streptomycetes, prolific producers of secondary metabolites with important biological activities. In the present study, we analysed Streptomyces coelicolor growth and differentiation in the presence of the hypo-methylating agent 5′-aza-2′-deoxycytidine (5-aza-dC) in order to investigate whether cytosine methylation has a role in differentiation. We found that cytosine demethylation caused a delay in spore germination, aerial mycelium development, sporulation, as well as a massive impairment of actinorhodin production. Thus, we searched for putative DNA methyltransferase genes in the genome and constructed a mutant of the SCO1731 gene. The analysis of the SCO1731::Tn5062 mutant strain demonstrated that inactivation of SCO1731 leads to a strong decrease of cytosine methylation and almost to the same phenotype obtained after 5-aza-dC treatment. Altogether, our data demonstrate that cytosine methylation influences morphological differentiation and actinorhodin production in S. coelicolor and expand our knowledge on this model bacterial system.

MADS-Box Transcription Factor MadsA Regulates Dimorphic Transition, Conidiation, and Germination of Talaromyces marneffei.

The opportunistic human pathogen Talaromyces marneffei exhibits a temperature-dependent dimorphic transition, which is closely related with its pathogenicity. This species grows as multinucleate mycelia that produce infectious conidia at 25°C, while undergoes a dimorphic transition to generate uninucleate yeast form cells at 37°C. The mechanisms of phenotype switching are not fully understood. The transcription factor madsA gene is a member of the MADS-box gene family. Previously, it was found that overexpression of madsA gene resulted in mycelial growth instead of yeast form at 37°C. In the current study, the madsA deletion mutant (ΔmadsA) and complemented strain (CMA) were constructed by genetic manipulation. We compared the phenotypes, growth, conidiation, conidial germination and susceptibility to stresses (including osmotic and oxidative) of the ΔmadsA with the wild-type (WT) and CMA strains. The results showed that the ΔmadsA displayed a faster process of the yeast-to-mycelium transition than the WT and CMA. In addition, the deletion of madsA led to a delay in conidia production and conidial germination. The tolerance of ΔmadsA conidia to hydrogen peroxide was better than that of the WT and CMA strains. Then, RNA-seq was performed to identify differences in gene expression between the ΔmadsA mutant and WT strain during the yeast phase, mycelium phase, yeast-to-mycelium transition and mycelium-to-yeast transition, respectively. Gene ontology functional enrichment analyses indicated that some important processes such as transmembrane transport, oxidation-reduction process, protein catabolic process and response to oxidative stress were affected by the madsA deletion. Together, our results suggest that madsA functions as a global regulator involved in the conidiation and germination, especially in the dimorphic transition of T. marneffei. Its roles in the survival, pathogenicity and transmission of T. marneffei require further investigation.

Control of seed dormancy and germination by DOG1-AHG1 PP2C phosphatase complex via binding to heme

Abscisic acid (ABA) regulates abiotic stress and developmental responses including regulation of seed dormancy to prevent seeds from germinating under unfavorable environmental conditions. ABA HYPERSENSITIVE GERMINATION1 (AHG1) encoding a type 2C protein phosphatase (PP2C) is a central negative regulator of ABA response in germination; however, the molecular function and regulation of AHG1 remain elusive. Here we report that AHG1 interacts with DELAY OF GERMINATION1 (DOG1), which is a pivotal positive regulator in seed dormancy. DOG1 acts upstream of AHG1 and impairs the PP2C activity of AHG1 in vitro. Furthermore, DOG1 has the ability to bind heme. Binding of DOG1 to AHG1 and heme are independent processes, but both are essential for DOG1 function in vivo. Our study demonstrates that AHG1 and DOG1 constitute an important regulatory system for seed dormancy and germination by integrating multiple environmental signals, in parallel with the PYL/RCAR ABA receptor-mediated regulatory system.

Germination of Indian Almond (Terminalia arjuna Roxb.) Seeds as Affected by Soil Salinity in Presence or Absence of Magnetic Iron

The hard seed coat is the major hindrance in achieving good and uniform germination for Indian almond (Terminalia arjuna Roxb.) fruits, especially when large plantations are to be raised under soil salinity stress. The present investigation was therefore, undertaken under the full sun at the nursery of Orman Botanical Garden, Giza during 2016 and 2017 seasons with the objective to find out the role of magnetic iron (Fe3O4) on mitigating the hazards of NaCl salinity, when applied at the rates of 0 or 3 g/20-cm-dimater plastic pot containing 10 fruits of arjuna and filled with about 3.5 kg of sand + clay mixture at equal parts (1:1, v/v) salinized with NaCl pure salt at the concentrations of 0, 2000, 4000, 6000 and 8000 ppm. The effect of interactions between Fe3O4 application rates and salinity levels was also studied in a complete randomized design experiment with factorial concept replicated thrice. The obtained results indicated that means of germination percentage were descendingly decreased with increasing salinity level to reach less than 50 % by 6000 and 8000 ppm levels, while planting the fruits in a soil mixture free from salt gave the highest germination %, followed by planting in 2000 ppm-salinized soil mixture, and then planting in soil mixture salinized with 4000 ppm concentration. On the other hand, addition of Fe3O4 (3 g/pot) significantly raised the mean of this measurement in both seasons. The shortest period to either maximum germination (G.V.) or 50 % germination (MGR) was achieved in both seasons by planting in non salinized control and 2000 ppm-salinized media, whereas increasing salinity level over that (up to 8000 ppm) prolonged these periods with the greatest delay in germination. On the contrary, Fe3O4 significantly reduced the means of such two traits causing a marked accelerating in G.V. and MGR. A slight increment was noticed in the means of germination rate index (GRI) by the different salinity concentrations, while Fe3O4 caused a trivial decrement. A similar response occurred as well regarding the means of vigour index (V.I.), seed viability (S.V.), hypocotyl length and vegetative and root growth attributes of the resulted seedlings. So, it can be advised to apply magnetic iron (Fe3O4) at the rate of 3 g/pot (20-cm-diameter) to improve germination and seedling quality of Terminalia arjuna Roxb. fruits planted in either low or medium salinized soil.

Large generative and vegetative reproduction independently increases global success of perennial plants from Central Europe

AbstractAimInvasion success of non‐native plants is known to be enhanced by high values in several performance‐related traits. As most studies have explored the traits in isolation, we do not know whether improved performance of invaders in some traits is negatively related to performance in other traits. Here, we examine associations between the alien success of Central European grassland species and several traits of generative and vegetative reproduction. We asked which reproductive characteristics are most important for alien success. We also investigated whether the most widespread non‐native species succeeded due to a weakened trade‐off between the traits.LocationGlobal with respect to alien success, and Central European with respect to origin of study species.MethodsIn greenhouse and garden conditions we measured traits of generative (seed mass, reproductive output, germination delay, germination rate, seedling weight) and vegetative reproduction (number and size of modules) of 85 perennial species native to Europe. We also compiled information on the ‘success’ of these species in exotic ranges from the Global Compendium of Weeds.ResultsAfter accounting for the effect of propagule pressure (which explained 30% of variance in the data), alien success was significantly and positively associated with germination rate, reproductive output and seedling weight, and with the product of these traits (termed generative reproduction), which explained 5%–13% of variance in the data. The best predictor of success was vegetative reproduction (product of module number and weight), which explained 19% of variance. However, more successful species resembled the less successful ones in following similar associations between the traits, such as the negative relationship between number and weight of modules or a non‐significant relationship between generative and vegetative reproduction.Main conclusionsHigh values of generative and vegetative reproduction pre‐adapt grassland perennial plants from Central Europe for global success. The success is, however, driven by an independent effect of the two reproductive modes and not by a weakened trade‐off between them.

The varied ability of grains to synthesize and catabolize ABA is one of the factors affecting dormancy and its release by after-ripening in imbibed triticale grains of cultivars with different pre-harvest sprouting susceptibilities

Abscisic acid (ABA) is a phytohormone involved in the acquisition of primary dormancy during seeds maturation as well as dormancy maintenance in imbibed seeds. After imbibition, the ABA content decreased to a much lower level in embryos of freshly harvested triticale grains of the Leontino cultivar, which is more susceptible to pre-harvest sprouting (PHS) than embryos of the Fredro cultivar. Lower ABA content in the Leontino cultivar resulted from increased expression of TsABA8′OH1 and TsABA8′OH2, which encode ABA 8′-hydroxylase and are involved in ABA catabolism. Higher ABA content and maintenance of dormancy in Fredro grains were correlated with intensified ABA biosynthesis, which resulted from higher expression of TsNCED1, which encodes 9-cis-epoxycarotenoid dioxygenase. These results suggest that grains of triticale cultivars with different resistance to PHS vary in their ability to metabolize ABA after imbibition.After-ripening did not affect the ABA content in embryos of dry grains of either triticale cultivar. However, after-ripening caused dormancy release in Fredro grains and significantly affected the ABA content and the rate of its metabolism after imbibition. A more rapid decline in ABA content in imbibed Fredro grains was accompanied by decreased transcript levels of TsNCED1 as well as increased expression of TsABA8′OH1 and TsABA8′OH2. Thus, after-ripening may affect dormancy of grains through reduction of the ABA biosynthesis rate and intensified ABA catabolism.Overexpression of TsNCED1 in tobacco increases ABA content and delays germination, while overexpression of TsABA8′OH2 decreases ABA content, accelerates germination, and reduces the sensitivity to ABA of transgenic seeds compared to seeds of wild-type plants. Therefore, these genes might play an important role in the regulation of triticale grain dormancy, thus affecting susceptibility to PHS.

Exploring the Role of Trehalose‐6‐phosphate Synthase in Oxidative Stress Tolerance of Fusarium verticillioides

Fusarium verticillioides is a filamentous fungus that infects maize and synthesizes fumonisins, a family of toxic and carcinogenic secondary metabolites. We are studying the role of trehalose in stress response in F. verticillioides. Trehalose‐6‐phosphate (T6P) synthase catalyzes the first step in trehalose synthesis, and a mutant lacking the gene that codes for T6P synthase does not produce trehalose or fumonisins. We report here that treatment with menadione or hydrogen peroxide inhibits germination of the mutant strain (Δtps1) more than the wild‐type strain. Whereas hydrogen peroxide delays germination, menadione reduces both the rate and percent germination, and significantly inhibits hyphal branching of both strains. To explore whether the sensitivity of Δtps1 to oxidative stress is caused by the lack of trehalose or the absence of a secondary function of the T6P synthase protein, we are studying mutants that express a catalytically inactive T6P synthase.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Moderate UV-A supplementation benefits tomato seed and seedling invigoration: a contribution to the use of UV in seed technology

Abstract The production, processing and consumption of Solanum lycopersicum L. fruits are increasing worldwide, demanding technologies to improve tomato growth efficiency. Germination is a critical step for intensification of crop production and conditions plants’ vigor, a crucial benchmark in plant market. Ultraviolet radiation supplementation is emerging in seed technology as it increases plant growth with no impact on the environment, although its use in crops’ nurseries still remains an open field. In the present work, seeds/seedlings of three commercial cultivars (‘Oxheart’, ‘Cherry’ and ‘Roma’) were grown for 15 days under three different ultraviolet (UV)-conditions. The results demonstrated the benefits of supplementing seeds/seedlings with moderate UV-A dose, being evident an acceleration/synchronization of germination rates, higher biomass and cotyledon area, and a stimulation of photosynthetic pigments and anthocyanins in all cultivars analysed. UV-B showed a cultivar dependence effect: ‘Cherry’ cultivar was in general not affected by the moderate UV-B dose used, but ‘Roma’ and ‘Oxheart’ showed a delay in germination and a seedling biomass decrease, in parallel with a decrease in chlorophylls and carotenoids. Both UV-A/B supplements reduced the H2O2 and MDA seedling levels, but the antioxidant battery was stimulated (e.g., peroxidases that use guaiacol as a substrate (GPX)) as well as the phenol level and the antiradical activity. The Principal Component Analysis (PCA) validates the clear distinction between cultivars and UV-condition effects. These data demonstrate the benefits of UV-A supplementation of tomato seeds pointing out to an “eustress” beneficial of UV-A in seedlings growth and vigor. A possible application of UV-A supplementation to other crops is discussed.

Changes in submerged aquatic vegetation (SAV) coverage caused by extended drought and flood pulses

ABSTRACTShivers SD, Golladay SW, Waters MN, Wilde SB, Ashford PD, Covich AP. 2018. Changes in submerged aquatic vegetation (SAV) coverage caused by extended drought and flood pulses. Lake Reserv Manage. 34:199—210.Previous studies demonstrated that submerged aquatic vegetation (SAV) affects productivity and biogeochemical cycling within freshwater ecosystems. Some invasive submerged macrophytes dominate shallow water bodies and are known to compete for nutrients with native macrophytes and phytoplankton. To evaluate variation in SAV coverage, annual whole-reservoir vegetation surveys were conducted during the peak of the growing season over a 3-yr period that included drought and years with seasonal flood pulses. Physical parameters were directly measured (Photosynthetically Active Radiation: PAR) or obtained from USGS river gauges (river discharge and turbidity) to investigate the relationship between hydrology and SAV coverage. Precipitation was lower in the first year of the study compared to the following 2 yr causing the lowest river discharge observed over the 3-yr study. First-year discharge was also lower than the 50-yr median daily Q (discharge). SAV coverage, particularly of dioecious Hydrilla verticillata, was the greatest during the reduced flow period (35.5 km2). With increasing precipitation and river discharge, SAV coverage was reduced during subsequent years (22.9 km2 and 18.3 km2, respectively). Increased discharge caused turbidity to increase, which reduced light availability during the early growing season, causing a delay in germination and subsequent reduction in SAV coverage. In shallow reservoirs, SAV is capable of extensive coverage. Thus, large variation in coverage can alter ecosystem functionality. In regulated river systems, managing late spring flood pulses may provide some control of SAV coverage in shallow reservoirs, in addition to providing other environmental flow benefits.

Elongator promotes germination and early post-germination growth

ABSTRACTThe Elongator complex interacts with RNA polymerase II and via histone acetylation and DNA demethylation facilitates epigenetically the transcription of genes involved in diverse processes in plants, including growth, development, and immune response. Recently, we have shown that the Elongator complex promotes hypocotyl elongation and photomorphogenesis in Arabidopsis thaliana by regulating the photomorphogenesis and growth-related gene network that converges on genes implicated in cell wall biogenesis and hormone signaling. Here, we report that germination in the elo mutant was delayed by 6 h in the dark when compared to the wild type in a time lapse and germination assay. A number of germination-correlated genes were down-regulated in the elo transcriptome, suggesting a transcriptional regulation by Elongator. We also show that the hypocotyl elongation defect observed in the elo mutants in darkness originates very early in the post-germination development and is independent from the germination delay.

Prognostic factors of primary gastrointestinal stromal tumors: a cohort study based on high-volume centers.

We aimed to evaluate the clinicopathologic characteristics, immunohistochemical expression and prognostic factors of patients with primary gastrointestinal stromal tumors (GISTs). Data from 2,570 consecutive GIST patients from four medical centers in China (January 2001-December 2015) were reviewed. Survival curves were constructed by the Kaplan-Meier method, and Cox regression models were used to identify independent prognostic factors. Of the included patients, 1,375 (53.5%) were male, and the patient age range was 18 to 95 (median, 58) years. The tumors were mostly found in the stomach (64.5%), small intestine (25.1%) and colorectal region (5.1%). At the time of diagnosis, the median tumor size was 4.0 (range: 0.1-55.0) cm, and the median mitotic index per 50 high power fields (HPFs) was 3 (range: 0-254). Of the 2,168 resected patients, 2,009 (92.7%) received curative resection. According to the modified National Institutes of Health (NIH) classification, 21.9%, 28.9%, 14.1% and 35.1% were very low-, low-, intermediate- and high-risk tumors, respectively. The rate of positivity was 96.4% for c-Kit, 87.1% for CD34, 96.9% for delay of germination 1 (DOG-1), 8.0% for S-100, 31.0% for smooth muscle actin (SMA) and 5.1% for desmin. However, the prognostic value of each was limited. Multivariate analysis showed that age, tumor size, mitotic index, tumor site, occurrence of curative resection and postoperative imatinib were independent prognostic factors. Furthermore, we found that high-risk patients benefited significantly from postoperative imatinib (P<0.001), whereas intermediate-risk patients did not (P=0.954). Age, tumor size, mitotic index, tumor site, occurrence of curative resection and postoperative imatinib were independent prognostic factors in patients with GISTs. Moreover, determining whether intermediate-risk patients can benefit from adjuvant imatinib would be of considerable interest in future studies.

ESSENTIAL OIL CHEMICAL CHARACTERIZATION AND ALLELOPATHIC POTENTIAL OF ARTEMISIA CAMPESTRIS L GROWING IN TUNISIA

The present study investigated the chemical composition and allelopathic potential of volatile oil from Artemisia campestris originating from Tunisia against four species: Daucus carota, Cicer arietinum, Phaseolus vulgaris and Triticum sativum. The essential oil was extracted using the hydrodistillation method and its composition was analyzed by gas chromatography coupled to mass spectrometry (GC-MS). Furthermore, the essential oil was tested for its inhibitory effect on seed germination of the four precited species. According to the main results, Artemisia campestris essential oil was rich in monoterpenoids and a total of 27 components were identified, accounting for 95.5% of the whole oil. Furthermore, β-pinene (35.0%) and 1, 8-cineole (14.4%) were the two major constituents. The volatile oil was evaluated for its allelopathic potential against the four fore-mentioned species. We noted a significant reduction in germination for all the tested species at 1000 ppm and 2000 ppm concentrations. However, an increase was noticed at the lowest concentration (100 ppm). Moreover, there was a delay in germination for D. carota seeds and this delay was proportional to the essential oil concentration. It is worthy to notice that Artemisia campestris essential oil exhibited allelopathic properties against the tested species and particularly against D. carota.

Combined transcriptome and translatome analyses reveal a role for tryptophan-dependent auxin biosynthesis in the control of DOG1-dependent seed dormancy.

The importance of translational regulation during Arabidopsis seed germination has been shown previously. Here the role of transcriptional and translational regulation during seed imbibition of the very dormant DELAY OF GERMINATION 1 (DOG1) near-isogenic line was investigated. Polysome profiling was performed on dormant and after-ripened seeds imbibed for 6 and 24h in water and in the transcription inhibitor cordycepin. Transcriptome and translatome changes were investigated. Ribosomal profiles of after-ripened seeds imbibed in cordycepin mimic those of dormant seeds. The polysome occupancy of mRNA species is not affected by germination inhibition, either as a result of seed dormancy or as a result of cordycepin treatment, indicating the importance of the regulation of transcript abundance. The expression of auxin metabolism genes is discriminative during the imbibition of after-ripened and dormant seeds, which is confirmed by altered concentrations of indole-3-acetic acid conjugates and precursors.