Screening of NIAS World Rice Core Collection for Seeds with Long Longevity as Useful Potential Breeding Materials Focusing on the Stability of Embryonic RNAs.

Seed longevity is a crucial trait for the seed industry and genetic resource preservation. To develop excellent cultivars with extended seed lifespans, it is important to understand the mechanism of keeping seed germinability long term and to find useful genetic resources as prospective breeding materials. This study was conducted to identify the best cultivars with a high and stable seed longevity trait in the germplasm of rice (Oryza sativa L.) and to analyze the correlation between seed longevity and embryonic RNA integrity. Seeds from 69 cultivars of the world rice core collection selected by the NIAS in Japan were harvested in different years and subjected to long-term storage or controlled deterioration treatment (CDT). The long-term storage (4 °C, RH under 35%, 10 years) was performed on seeds harvested in 2010 and 2013. The seeds harvested in 2016 and 2019 were used for CDT (36 °C, RH of 80%, 40 days). Seed longevity and embryonic RNA integrity were estimated by a decrease in the germination percentage and RNA integrity number (RIN) after long-term storage or CDT. The RIN value was obtained by the electrophoresis of the total RNA extracted from the seed embryos. Seeds of "Vandaran (indica)", "Tupa 729 (japonica)", and "Badari Dhan (indica)" consistently showed higher seed longevity and embryonic RNA integrity both under long-term storage and CDT conditions regardless of the harvest year. A strong correlation (R2 = 0.93) was observed between the germination percentages and RIN values of the seeds after the long-term storage or CDT among nine cultivars selected based on differences in their seed longevity. The study findings revealed the relationship between rice seed longevity and embryo RNA stability and suggested potential breeding materials including both japonica and indica cultivars for improving rice seed longevity.

Aging-Induced Reduction in Safflower Seed Germination via Impaired Energy Metabolism and Genetic Integrity Is Partially Restored by Sucrose and DA-6 Treatment.

Seed storage underpins global agriculture and the seed trade and revealing the mechanisms of seed aging is essential for enhancing seed longevity management. Safflower is a multipurpose oil crop, rich in unsaturated fatty acids that are at high risk of peroxidation as a contributory factor to seed aging. However, the molecular mechanisms responsible for safflower seed viability loss are not yet elucidated. We used controlled deterioration (CDT) conditions of 60% relative humidity and 50 °C to reduce germination in freshly harvested safflower seeds and analyzed aged seeds using biochemical and molecular techniques. While seed malondialdehyde (MDA) and fatty acid content increased significantly during CDT, catalase activity and soluble sugar content decreased. KEGG analysis of gene function and qPCR validation indicated that aging severely impaired several key functional and biosynthetic pathways including glycolysis, fatty acid metabolism, antioxidant activity, and DNA replication and repair. Furthermore, exogenous sucrose and diethyl aminoethyl hexanoate (DA-6) treatment partially promoted germination in aged seeds, further demonstrating the vital role of impaired sugar and fatty acid metabolism during the aging and recovery processes. We concluded that energy metabolism and genetic integrity are impaired during aging, which contributes to the loss of seed vigor. Such energy metabolic pathways as glycolysis, fatty acid degradation, and the tricarboxylic acid cycle (TCA) are impaired, especially fatty acids produced by the hydrolysis of triacylglycerols during aging, as they are not efficiently converted to sucrose via the glyoxylate cycle to provide energy supply for safflower seed germination and seedling growth. At the same time, the reduced capacity for nucleotide synthesis capacity and the deterioration of DNA repair ability further aggravate the damage to DNA, reducing seed vitality.

TMT-based quantitative proteomic and physiological analyses on lotus plumule of artificially aged seed in long-living sacred lotus Nelumbo nucifera.

Seed longevity is important for the maintenance of seed nutritional quality, vigor, and germination potential during storage. Sacred lotus is known as one of the longest living seeds in the world and their ability to maintain longevity has been widely investigated. In this study, a suitable controlled deterioration treatment (CDT) method was first established to evaluate the vigor loss of lotus plumule (LP), and then the Tandem Mass Tags (TMT)-based proteomic analysis was performed on LP from the CDT-treated seed to quantitatively and qualitatively analyze the protein profile dynamic. In total, 4002 proteins were successfully quantified, of them, 558 differently accumulated proteins (DAPs) were identified. Protein processing and RNA-related proteins were found more easily to be affected by CDT, which may directly result in seed vigor loss. Meanwhile, CDT resulted in remarkable up-regulation of numerous proteins related to antioxidation, photosynthesis, RNA and DNA stability, starch and sucrose mobilization, and cell membrane and wall stability, which potentially played key roles in maintaining the lotus seed vigor under CDT. Histological and physiological analyses were also performed to verify some proteome results. This study provided both fundamental data and new insights to further uncover the secret of lotus seed longevity. SIGNIFICANCE: Seed aging affects the seed quality and can result in direct economic losses. The exceptional longevity of sacred lotus seed has attracted extensive attention. In this study, an optimized CDT method was used to mimic the natural aging process of sacred lotus seed, and based on TMT-based quantitative proteomic analysis on the LP profile of CDT-treated seeds, a series of differentially accumulation of specific proteins (DEPs) were revealed related to CDT resistance. Correspondingly, the physiological state and histological structure of the LP along with the CDT were detected to verify the proteome data. This study provided comprehensive information for the molecular basis of lotus seed aging analysis and facilitate to screen seed longevity related proteins for other plant species.

Transcriptional multiomics reveals the mechanism of seed deterioration in Nicotiana tabacum L. and Oryza sativa L.

INTRODUCTION: Mature seeds deteriorate gradually and die eventually during long-term storage. Controlled deterioration is often used to accelerate the seed deterioration rate to assess the seed vigor and physiological quality of seed lots. OBJECTIVES: Although it is well known that the process of seed deterioration produced by controlled deterioration is distinct from that caused by long-term storage, the differences in transcriptional levels have not been reported. Clarifying the mechanism of seed deterioration is critical for identifying, conserving and utilizing germplasm resources. METHODS: Tobacco (Nicotiana tabacum L.) seeds were studied thoroughly using transcriptome, small RNA, and degradome sequencing after long-term storage (LS) and controlled deterioration (CD). Co-expression trend analysis identified transcripts involved in tobacco seed deterioration, while phylogenetic analysis helped to uncover comparable targets in rice (Oryza sativa L.) for further verification and utilization. RESULTS: In LS and CD, a total of 2,112 genes and 164 miRNAs were differentially expressed, including 20 interaction miRNA-mRNA pairs with contrasting expression. Transcriptional multiomics found that the main causes of LS were plant hormone signal transduction and protein processing in the endoplasmic reticulum, whereas the primary cause of CD was nucleotide excision repair dysfunction. The homeostatic balance of RNA degradation and the spliceosome occurred in both modes of seed deterioration. Additionally, co-expression trend analysis identified two coherent pairs, nta-miR160b-NtARF18 and nta-miR396c-NtMBD10, as being significant in LS and CD, respectively. For utilization, rice homologous targets OsARF18 and OsMBD707 were verified to play similar roles in LS and CD, respectively. CONCLUSION: This study demonstrated the transcriptional mechanism of tobacco and key genes in seed deterioration. And the application of key genes in rice also verified the feasibility of the multiomics method, guiding the identification of candidate genes to precisely delay seed deterioration in other species of seed research.

Comparative changes in sugars and lipids show evidence of a critical node for regeneration in safflower seeds during aging.

During seed aging, there is a critical node (CN) where the population viability drops sharply. Exploring the specific locations of the CN in different species of plants is crucial for understanding the biological storage properties of seeds and refining seed life span management. Safflower, a bulk oil crop that relies on seeds for propagation, has a short seed life. However, at present, its biological characteristics during storage are not clear, especially the changes in metabolic capability and cell structures. Such knowledge is needed to improve the management of safflower seed life span and effective preservation in gene banks. Here, the seed survival curve of oilseed safflower under the controlled deterioration conditions of 60% relative humidity and 50°C was detected. The seed population showed an inverted S shape for the fall in germination. In the first 12 days of aging, germination remained above 86%. Prior to the CN at approximately day 10 (C10), when viability was in the "plateau" interval, seed vigor reduced at the same imbibition time point. Further analysis of the changes in sugar concentration found that the sucrose content decreased slowly with aging and the content of raffinose and two monosaccharides decreased abruptly at C10. Differentially metabolized lipids, namely lysophospholipids [lyso-phosphatidylcholine (LPC) and lyso-phosphatidylethanolamines (LPE)] and PMeOH, increased at day 3 of aging (C3). Fatty acid content increased by C6, and the content of phospholipids [phosphatidylcholines (PC), phosphatidylethanolamines (PE), and phosphatidylinositols (PI) and glycolipids [digalactosyl diacylglycerol, monogalactosyl diacylglycerol, and sulphoquinovosyl diglycerides (SQDG)] decreased significantly from C10. In addition, the activities of raffinose hydrolase alpha-galactosidase and the glyoxylate key enzyme isocitrate lyase decreased with seed aging. Confocal microscopy and transmission electron microscopy revealed shrinkage of the seed plasma membrane at C10 and the later fragmentation. Seedling phenotypic indicators and 2,3,5-triphenyltetrazolium chloride activity assays also verified that there were significant changes in seeds quality at the CN. In summary, the time point C10 is a CN during seed population aging. Before the CN, sugar and lipid metabolism, especially fatty acid metabolism into sugar, can make up for the energy consumed by aging. After this point, the seeds were irreversibly damaged, and their viability was greatly and rapidly reduced as the cell structure became increasingly destroyed.

Does oxygen affect ageing mechanisms of Pinus densiflora seeds? A matter of cytoplasmic physical state.

During desiccation, the cytoplasm of orthodox seeds solidifies into an intracellular glass with highly restricted diffusion and molecular mobility. Temperature and water content govern seed ageing rates, while oxygen (O2) can promote deteriorative reactions. However, whether the cytoplasmic physical state affects involvement of O2 in seed ageing remains unresolved. We aged Pinus densiflora seeds by controlled deterioration (CD) at 45 °C and distinct relative humidity (RH), resulting in cells with a glassy (11% and 30% RH) or fluid (60% and 80% RH) cytoplasm. Hypoxic conditions (0.4% O2) during CD delayed seed deterioration, lipid peroxidation, and decline of antioxidants (glutathione, α-tocopherol, and γ-tocopherol), but only when the cytoplasm was glassy. In contrast, when the cytoplasm was fluid, seeds deteriorated at the same rate regardless of O2 availability, while being associated with limited lipid peroxidation, detoxification of lipid peroxide products, substantial loss of glutathione, and resumption of glutathione synthesis. Changes in metabolite profiles provided evidence of other O2-independent enzymatic reactions in a fluid cytoplasm, including aldo-keto reductase and glutamate decarboxylase activities. Biochemical profiles of seeds stored under seed bank conditions resembled those obtained after CD regimes that maintained a glassy cytoplasm. Overall, O2 contributed more to seed ageing when the cytoplasm was glassy, rather than fluid.

Characteristics and functions of glyceraldehyde 3-phosphate dehydrogenase S-nitrosylation during controlled aging of elm and Arabidopsis seeds.

Seed aging is the gradual decline in seed vigor, during which programmed cell death (PCD) occurs. The functions of nitric oxide (NO) are exerted through protein S-nitrosylation, a reversible post-translational modification. During seed aging, more than 80 proteins are S-nitrosylated, but the particular role of individual proteins is unknown. Here, we showed that the S-nitrosylation level of glyceraldehyde 3-phosphate dehydrogenase (UpGAPDH) in elm (Ulmus pumila L.) seeds increased after controlled deterioration treatment. UpGAPDH was S-nitrosylated at Cys154 during S-nitrosoglutathione (GSNO) treatment, and its oligomerization was triggered both in vitro and in elm seeds. Interestingly, UpGAPDH interacted with the mitochondrial voltage-dependent anion channel in an S-nitrosylation-dependent way. Some UpGAPDH-green fluorescent protein in Arabidopsis protoplasts co-localized with mitochondria during the GSNO treatment, while the S-nitrosylation-defective UpGAPDH C154S-GFP protein did not. Seeds of oxUpGAPDH lines showed cell death and lost seed vigor rapidly during controlled deterioration treatment-triggered seed aging, while those overexpressing S-nitrosylation-defective UpGAPDH-Cys154 did not. Our results suggest that S-nitrosylation of UpGAPDH may accelerate cell death and seed deterioration during controlled deterioration treatment. These results provide new insights into the effects of UpGAPDH S-nitrosylation on protein interactions and seed aging.

QTL analysis of seed germination traits in tobacco (Nicotiana tabacum L.).

Genetic mapping of seed germination traits has been performed with many plant species. In tobacco, however, investigations are rare. In the present study, a bi-parental mapping population consisting of 118 doubled haploid lines and derived from a cross between 'Beinhart-1000' and 'Hicks' was investigated. Four germination-related traits, total germination (TG), normal germination (NG), time to reach 50% of total germination (T50), and the area under the curve after 200 h of germination (AUC) were considered by examining seeds either untreated or after a moderate controlled deterioration (CD). Quantitative trait loci were found for all traits distributed on 11 out of the 24 linkage groups. It was demonstrated that, as in many other species, germination-related traits are very complex and under polygenic control.

Effects of Inorganic Salt Solutions on Vigour, Viability, Oxidative Metabolism and Germination Enzymes in Aged Cabbage and Lettuce Seeds.

This study assessed the potential of pre-hydration treatment with aqueous solutions (electrolysed [cathodic water; CW] and non-electrolysed) prepared from four different inorganic ion combinations: 1 mM CaCl2, 1 µm CaCl2 and 1 mM MgCl2 (CaMg, hereafter), 1 mM MgCl2 and 1 mM NaCl to invigorate controlled deteriorated (CDd) Brassicaoleracea (cabbage) and Lactucasativa (lettuce) seeds by assessing germination, vigour and biochemical markers (electrolyte leakage, lipid peroxidation products, protein carbonylation, and defence and germination associated enzymes) of oxidative stress. Additionally, the possible effects of pH of electrolysed CaMg and NaCl solutions were assessed. The inorganic salt solutions were applied to fresh seeds and seeds deteriorated to 75% viability (P75), 50% viability (P50) and 25% viability (P25); deionised water served as control. The pre-hydration treatment did not enhance normal seedling production in cabbage. However, Ca-containing and CW hydration treatments (CaCl2 CW, CaMg and CaMg CW [6.5], MgCl2 CW, NaCl CW and NaCl CW [6.5]) promoted normal seedling production of CDd lettuce seeds, while seedling vigour was enhanced by CaMg, CaMg CW (6.5), NaCl CW and NaCl CW (6.5) in CDd cabbage seeds, and CaCl2, CaCl2 CW, CaMg, CaMg CW (6.5), MgCl2 CW, NaCl CW and NaCl CW (6.5) in CDd lettuce seeds. The supplementation of Ca, a component of the ionised solutes, and/or the reducing potential of CW contributed to increased normal seedling production in lettuce seeds irrespective of the pH of treatment solutions or degree of deterioration. Overall, the pre-hydration treatments enhanced endogenous antioxidants leading to reduced levels of electrolyte leakage, lipid peroxidation, protein carbonylation, and enhanced germination enzyme activities in lettuce seeds. The study concluded that pre-hydration with selected inorganic salt solutions can invigorate debilitated lettuce seeds.

Influence of Cathodic Water Invigoration on the Emergence and Subsequent Growth of Controlled Deteriorated Pea and Pumpkin Seeds.

The quality of seeds in gene banks gradually deteriorates during long-term storage, which is probably, at least in part, a result of the progressive development of oxidative stress. Here, we report a greenhouse study that was carried out to test whether a novel approach of seed invigoration using priming with cathodic water (cathodic portion of an electrolysed calcium magnesium solution) could improve seedling emergence and growth in two deteriorated crop seeds. Fresh seeds of Pisum sativum and Cucurbita pepo were subjected to controlled deterioration to 50% viability at 14% seed moisture content (fresh weight basis), 40 °C and 100% relative humidity. The deteriorated seeds were thereafter primed with cathodic water, calcium magnesium solution and deionized water. In addition, to study the mechanism of the impacts of invigoration, the effects of such priming on the lipid peroxidation products malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) and on the reactive oxygen species (ROS) scavenging enzymes superoxide dismutase and catalase were also determined in the fresh and deteriorated seeds. All priming treatments improved seed emergence parameters, subsequent seedling photosynthesis and growth relative to the unprimed seeds. In general, cathodic water was most effective at invigorating deteriorated seeds. Analysis of the lipid peroxidation products and antioxidant enzyme activities in invigorated seeds provided support for the hypothesis that the effectiveness of cathodic water in invigoration of debilitated orthodox seeds in general and of pea and pumpkin seeds in particular derive from its ability to act as an antioxidant.

The effects of high oxygen partial pressure on vegetable Allium seeds with a short shelf-life.

MAIN CONCLUSION: Storage at an elevated partial pressure of oxygen and classical artificial ageing cause a rapid loss of seed viability of short-lived vegetable seeds. Prolonging seed longevity during storage is of major importance for gene banks and the horticultural industry. Slowing down biochemical deterioration, including oxygen-dependent deterioration caused by oxidative processes can boost longevity. This can be affected by the seed structure and the oxygen permeability of seed coat layers. Classical artificial seed ageing assays are used to estimate seed 'shelf-life' by mimicking seed ageing via incubating seeds at elevated temperature and elevated relative humidity (causing elevated equilibrium seed moisture content). In this study, we show that seed lots of vegetable Allium species are short-lived both during dry storage for several months and in seed ageing assays at elevated seed moisture levels. Micromorphological analysis of the Allium cepa x Allium fistulosum salad onion seed identified intact seed coat and endosperm layers. Allium seeds equilibrated at 70% relative humidity were used to investigate seed ageing at tenfold elevated partial pressure of oxygen (high pO2) at room temperature (22 ºC) in comparison to classical artificial ageing at elevated temperature (42 ºC). Our results reveal that 30 days high pO2 treatment causes a rapid loss of seed viability which quantitatively corresponded to the seed viability loss observed by ~ 7 days classical artificial ageing. A similar number of normal seedlings develop from the germinating (viable) proportion of seeds in the population. Many long-lived seeds first exhibit a seed vigour loss, evident from a reduced germination speed, preceding the loss in seed viability. In contrast to this, seed ageing of our short-lived Allium vegetable seems to be characterised by a rapid loss in seed viability.

Genome-Wide Linkage Mapping Reveals QTLs for Seed Vigor-Related Traits Under Artificial Aging in Common Wheat (Triticum aestivum).

Long-term storage of seeds leads to lose seed vigor with slow and non-uniform germination. Time, rate, homogeneity, and synchrony are important aspects during the dynamic germination process to assess seed viability after storage. The aim of this study is to identify quantitative trait loci (QTLs) using a high-density genetic linkage map of common wheat (Triticum aestivum) for seed vigor-related traits under artificial aging. Two hundred and forty-six recombinant inbred lines derived from the cross between Zhou 8425B and Chinese Spring were evaluated for seed storability. Ninety-six QTLs were detected on all wheat chromosomes except 2B, 4D, 6D, and 7D, explaining 2.9-19.4% of the phenotypic variance. These QTLs were clustered into 17 QTL-rich regions on chromosomes 1AL, 2DS, 3AS (3), 3BS, 3BL (2), 3DL, 4AS, 4AL (3), 5AS, 5DS, 6BL, and 7AL, exhibiting pleiotropic effects. Moreover, 10 stable QTLs were identified on chromosomes 2D, 3D, 4A, and 6B (QaMGT.cas-2DS.2, QaMGR.cas-2DS.2, QaFCGR.cas-2DS.2, QaGI.cas-3DL, QaGR.cas-3DL, QaFCGR.cas-3DL, QaMGT.cas-4AS, QaMGR.cas-4AS, QaZ.cas-4AS, and QaGR.cas-6BL.2). Our results indicate that one of the stable QTL-rich regions on chromosome 2D flanked by IWB21991 and IWB11197 in the position from 46 to 51 cM, presenting as a pleiotropic locus strongly impacting seed vigor-related traits under artificial aging. These new QTLs and tightly linked SNP markers may provide new valuable information and could serve as targets for fine mapping or markers assisted breeding.

QTL analysis of falling number and seed longevity in wheat (Triticum aestivum L.).

Pre-harvest sprouting (PHS) and seed longevity (SL) are complex biological processes of major importance for agricultural production. In the present study, a recombinant inbred line (RIL) population derived from a cross between the German winter wheat (Triticum aestivum L.) cultivars History and Rubens was used to identify genetic factors controlling these two physiological seed traits. A falling number (FN) test was employed to evaluate PHS, while SL was measured using a germination test (and the speed of germination) after controlled deterioration. FN of the population was assessed in four environments; SL traits were measured in one environment. Four major quantitative trait loci (QTL) for FN were detected on chromosomes 4D, 5A, 5D, and 7B, whereas for SL traits, a major QTL was found on chromosome 1A. The FN QTL on chromosome 4D that coincided with the position of the dwarfing gene Rht-D1b only had effects in environments that were free of PHS. The remaining three QTL for FN were mostly pronounced under conditions conducive to PHS. The QTL on the long arm of chromosome 7B corresponded to the major gene locus controlling late maturity α-amylase (LMA) in wheat. The severity of the LMA phenotype became truly apparent under sprouting conditions. The position on the long arm of chromosome 1A of the QTL for SL points to a new QTL for this important regenerative seed trait.

In-depth proteomic analysis of Glycine max seeds during controlled deterioration treatment reveals a shift in seed metabolism.

Seed aging is one of the major events, affecting the overall quality of agricultural seeds. To analyze the effect of seed aging, soybean seeds were exposed to controlled deterioration treatment (CDT) for 3 and 7days, followed by their physiological, biochemical, and proteomic analyses. Seed proteins were subjected to protamine sulfate precipitation for the enrichment of low-abundance proteins and utilized for proteome analysis. A total of 14 differential proteins were identified on 2-DE, whereas label-free quantification resulted in the identification of 1626 non-redundant proteins. Of these identified proteins, 146 showed significant changes in protein abundance, where 5 and 141 had increased and decreased abundances, respectively while 352 proteins were completely degraded during CDT. Gene ontology and KEGG analyses suggested the association of differential proteins with primary metabolism, ROS detoxification, translation elongation and initiation, protein folding, and proteolysis, where most, if not all, had decreased abundance during CDT. Western blotting confirmed reduced level of antioxidant enzymes (DHAR, APx1, MDAR, and SOD) upon CDT. This in-depth integrated study reveals a major downshift in seed metabolism upon CDT. Reported data here serve as a resource for its exploitation to metabolic engineering of seeds for multiple purposes, including increased seed viability, vigor, and quality. BIOLOGICAL SIGNIFICANCE: Controlled deterioration treatment (CDT) is one of the major events that negatively affects the quality and nutrient composition of agricultural seeds. However, the molecular mechanism of CDT is largely unknown. A combination of gel-based and gel-free proteomic approach was utilized to investigate the effects of CDT in soybean seeds. Moreover, we utilized protamine sulfate precipitation method for enrichment of low-abundance proteins, which are generally masked due to the presence of high-abundance seed storage proteins. Reported data here serve as resource for its exploitation to metabolic engineering of seeds for multiple purposes, including increased seed viability, vigor, and quality.

Ectopic expression of NnPER1, a Nelumbo nucifera 1-cysteine peroxiredoxin antioxidant, enhances seed longevity and stress tolerance in Arabidopsis.

Seed longevity, the maintenance of viability during storage, is a major factor for conservation of genetic resources and biodiversity. Seed longevity is an important trait of agriculture crop and is impaired by reactive oxygen species (ROS) during seed desiccation, storage and germination (C. R. Biol., 331, 2008 and 796). Seeds possess a wide range of systems (protection, detoxification, repair) allowing them to survive during storage and to preserve a high germination ability. In many plants, 1-cys peroxiredoxin (1-Cys Prx, also named PER1) is a seed-specific antioxidant which eliminates ROS with cysteine residues. Here we identified and characterized a seed-specific PER1 protein from seeds of sacred lotus (Nelumbo nucifera Gaertn.). Purified NnPER1 protein protects DNA against the cleavage by ROS in the mixed-function oxidation system. The transcription and protein accumulation of NnPER1 increased during seed desiccation and imbibition and under abiotic stress treatment. Ectopic expression of NnPER1 in Arabidopsis enhanced the seed germination ability after controlled deterioration treatment (CDT), indicating that NnPER1 improves seed longevity of transgenic plants. Consistent with the function of NnPER1 on detoxifying ROS, we found that the level of ROS release and lipid peroxidation was strikingly lower in transgenic seeds compared to wild-type with or without CDT. Furthermore, transgenic Arabidopsis seeds ectopic-expressing NnPER1 displayed enhanced tolerance to high temperature and abscisic acid (ABA), indicating that NnPER1 may participate in the thermotolerance and ABA signaling pathway.

The inheritance of wheat grain longevity: a comparison between induced and natural ageing.

Seed longevity is an important trait for both ex situ genebanks and the seed industry. It is partially determined by genetic factors, but is also dependent on the environmental conditions experienced by the mother plant during seed maturation, as well as those imposed during the post-harvest and storage periods. For practical reasons, the variation in longevity has repeatedly been analysed by treating fresh seed to various induced ageing protocols, but the extent to which these procedures mimic the natural ageing process remains debatable. Here, a comparison was attempted between the wheat genomic regions identified by biparental mapping as harbouring determinants of viability loss identified in grain which had been either aged artificially or had been stored long term. Only one locus proved to be shared, but even here, the parental origin of the positive allele differed. Correlation analysis revealed no relationship between various induced ageing treatments and long-term storage.

Physiological and proteomic analyses on artificially aged Brassica napus seed.

Plant seeds lose their viability when they are exposed to long term storage or controlled deterioration treatments, by a process known as seed aging. Based on previous studies, artificially aging treatments have been developed to accelerate the process of seed aging in order to understand its underlying mechanisms. In this study, we used Brassica napus seeds to investigate the mechanisms of aging initiation. B. napus seeds were exposed to artificially aging treatment (40°C and 90% relative humidity) and their physio-biochemical characteristics were analyzed. Although the treatment delayed germination, it did not increase the concentration of cellular reactive oxygen species (ROS). Comparative proteomic analysis was conducted among the control and treated seeds at different stages of germination. The proteins responded to the treatment were mainly involved in metabolism, protein modification and destination, stress response, development, and miscellaneous enzymes. Except for peroxiredoxin, no changes were observed in the accumulation of other antioxidant enzymes in the artificially aged seeds. Increased content of abscisic acid (ABA) was observed in the artificially treated seeds which might be involved in the inhibition of germination. Taken together, our results highlight the involvement of ABA in the initiation of seed aging in addition to the ROS which was previously reported to mediate the seed aging process.

Reactive oxygen species-provoked mitochondria-dependent cell death during ageing of elm (Ulmus pumila L.) seeds.

Previous studies have shown that controlled deterioration treatment (CDT) induces programmed cell death in elm (Ulmus pumila L.) seeds, which undergo certain fundamental processes that are comparable to apoptosis in animals. In this study, the essential characteristics of mitochondrial physiology in elm seeds during CDT were identified by cellular ultrastructural analysis, whole-body optical imaging, Western blotting and semi-quantitative RT-PCR. The alteration in mitochondrial morphology was an early event during CDT, as indicated by progressive dynamic mitochondrial changes and rupture of the mitochondrial outer membrane; loss of mitochondrial transmembrane potential (Δψ(m)) ensued, and mitochondrial ATP levels decreased. The mitochondrial permeability transition pore inhibitor cyclosporine A effectively suppressed these changes during ageing. The in situ localization of production of reactive oxygen species (ROS), and evaluation of the expression of voltage-dependent anion-selective channel and cyclophilin D indicated that the levels of mitochondrial permeability transition pore components were positively correlated with ROS production, leading to an imbalance of the cellular redox potential and ultimately to programmed cell death. Pre-incubation with ascorbic acid slowed loss of mitochondrial Δψ(m), and decreased the effect of CDT on seed viability. However, there were no significant changes in multiple antioxidant elements or chaperones in the mitochondria during early stages of ageing. Our results indicate that CDT induces dynamic changes in mitochondrial physiology via increased ROS production, ultimately resulting in an irreversible loss of seed viability.

Peroxidase activity in scutella of maize in association with anatomical changes during germination and grain storage.

The embryo of the maize grain (Zea mays L.) is separated from the starchy endosperm by a fibrous structure, which is called the fibrous layer (FL). Using histochemical staining, it was determined that the FL is composed of collapsed cellular layers that contain phenols, neutral lipids, and 1,3-ß-glucan. Due to its composition, the FL prevents free diffusion and separates the embryo from the endosperm during germination. Twenty-four hours after imbibition, the scutellum epidermis initiated a series of asynchronous spatial modifications, including cell growth, the perforation of cell walls, increased peroxidase activity in the apoplastic space, and elevated levels of superoxide, phenols, and other components that interact with the fibrous layer, enabling its transformation in addition to the free flow between compartments. During storage at high relative humidity levels, which leads to fast or slow deterioration depending on the temperature, the activity of phenol peroxidase in the scutellum was associated with a loss of vigor and reduced germination capacity when compared with low temperature and low relative humidity conditions. Such deterioration is associated with alterations in autofluorescent emissions from endogenous compounds in the scutellum, indicating changes in the microenvironment or in the differential proportions of epidermal and FL components.

Testes de vigor em sementes de Crambe abyssinica / Vigor tests of Crambe abyssinica seeds

O objetivo deste trabalho foi verificar a eficiência de testes de vigor na avaliação da qualidade fisiológica de sementes de crambe. Para isso, quatro lotes de sementes de crambe da cultivar 'FMS Brilhante' foram submetidos aos testes de germinação e vigor (primeira contagem de germinação, comprimento e massa seca de plântula, emergência de plântulas em areia e campo, condutividade elétrica, envelhecimento acelerado e deterioração controlada), em delineamento inteiramente casualizado com quatro repetições. Os testes de emergência de plântulas em campo e de deterioração controlada com sementes pré umedecidas a 15% e mantidas a 42°C/48 horas e a 25% a 45°C/36 horas são eficientes na classificação dos lotes de sementes de crambe em distintos níveis de vigor.

The objective was to verify vigor tests efficiency in the evaluation the crambe seeds physiological quality. Four lots of crambe seeds of cultivar 'FMS Brilhante' were submitted to the following standard germination and vigour test (first germination count, length and dry mass of seedling, seedling emergence in sand and field, electrical conductivity, accelerated ageing and controlled deterioration). The experiment was conducted in a randomized complete block design for test, evaluating the lots effect. The seedling emergence in field test and the controlled deterioration test at pre-moistened seeds at 15% and maintained under 42°C/48h and at 25% under 45°C/36h are efficients classifying the crambe seeds lots in different vigour levels.