Promotive effects of alginate-derived oligosaccharide on maize seed germination

The influence of alginate-derived oligosaccharide (molecular weight 1445 Da) was tested on the maize seed germination at different concentrations. Assays of α-and β-amylase and protease activities showed the highest response at 0.75‰.Compared with the control, root growth on days 3 and 7 showed increases of 34% and18%, respectively; and shoot growth on day 7 an increase of 46%. In the case of protease activity, treatments with both 0.75‰ and 1.50‰ alginate-derived oligosaccharide gave higher activities than the control. These results indicate that the rate of seed germination was enhanced by increasing the activities of several enzymes beneficial for germination. This revised version was published online in August 2006 with corrections to the Cover Date.     

MicroRNA transcriptomic analysis of heterosis during maize seed germination

Heterosis has been utilized widely in the breeding of maize and other crops, and plays an important role in increasing yield, improving quality and enhancing stresses resistance, but the molecular mechanism responsible for heterosis is far from clear. To illustrate whether miRNA-dependent gene regulation is responsible for heterosis during maize germination, a deep-sequencing technique was applied to germinating embryos of a maize hybrid, Yuyu22, which is cultivated widely in China and its parental inbred lines, Yu87-1 and Zong3. The target genes of several miRNAs showing significant expression in the hybrid and parental lines were predicted and tested using real-time PCR. A total of 107 conserved maize miRNAs were co-detected in the hybrid and parental lines. Most of these miRNAs were expressed non-additively in the hybrid compared to its parental lines. These results indicated that miRNAs might participate in heterosis during maize germination and exert an influence via the decay of their target genes. Novel miRNAs were predicted follow a rigorous criterion and only the miRNAs detected in all three samples were treated as a novel maize miRNA. In total, 34 miRNAs belonged to 20 miRNA families were predicted in germinating maize seeds. Global repression of miRNAs in the hybrid, which might result in enhanced gene expression, might be one reason why the hybrid showed higher embryo germination vigor compared to its parental lines.     

Toward characterizing seed vigor in alfalfa through proteomic analysis of germination and priming

Alfalfa, the most widely grown leguminous crop in the world, is generally exposed to severe salinity stress in Tunisia, notably affecting its germination performance. Toward a better understanding of alfalfa seed vigor, we have used proteomics to characterize protein changes occurring during germination and osmopriming, a pretreatment that accelerates germination and improves seedling uniformity particularly under stress conditions. The data revealed that germination was accompanied by dynamic changes of 79 proteins, which are mainly involved in protein metabolism, cell structure, metabolism, and defense. Comparative proteomic analysis also revealed 63 proteins specific to osmopriming, 65 proteins preferentially varying during germination, and 14 proteins common to both conditions. Thus, the present study unveiled the unexpected finding that osmopriming cannot simply be considered as an advance of germination-related processes but involves other mechanisms improving germination such as the mounting of defense mechanisms enabling osmoprimed seeds to surmount environmental stresses potentially occurring during germination. The present results therefore provide novel avenues toward understanding the mechanisms of invigoration of low vigor seeds by priming treatments that are widely used both in commercial applications and in developing countries (on farm seed priming) to better control crop yields.     

Cadmium exposure triggers genotype-dependent changes in seed vigor and germination of tomato offspring

Although negative effects on the offspring fitness can be triggered by the mother-plant exposure to environmental stresses, some plants are able to “remember” past incidents and enhance the progeny tolerance. Here, the mineral profile, cytogenetic modifications, and physiological potential of seeds from two tomato cultivars, with contrasting tolerance degrees to cadmium (Cd) toxicity, were evaluated after plant exposure to this metal. Both cultivars exhibited high Cd translocation to the seeds; however, the tolerant tomato accumulated more Cd than did the sensitive one. As a consequence of the Cd accumulation, reductions in the Mn concentration in Cd-challenged plants were detected. Surprisingly, seed germination and vigor were increased in the tolerant tomato cultivar after Cd exposure, despite increases in the chromosomal abnormalities. By contrast, seeds from the sensitive cultivar exhibited no changes in their physiological potential after Cd exposure, despite Cd-induced reductions in the mitotic index. Moreover, bunch position exerted effects on the vigor and type of chromosomal abnormality. The results show that maternal plant exposure to Cd can affect tomato offspring by changing the seed physiological potential, and such effect can be partially explained by alterations in the seed-derived elements (essential and non-essential) and genotype-dependent tolerance mechanisms.     

Functional genomics in the study of seed germination

A recent proteomic analysis of germinating Arabidopsis thaliana seeds demonstrates the effectiveness of functional genomics for investigating the complexity of developmental regulatory networks, such as the development of the embryo into a young plant.     

Polyamine distribution among maize embryonic tissues and its relation to seed germination

Polyamines are known to participate in the control of cell division. In the present report, the levels and distribution of polyamines in the embryonic tissues of maize seeds were studied to relate them to the reinitiation of cell division during seed germination. Results indicate higher contents of polyamines in scutellum than in axis tissues of dry seeds. After germination, larger increments of the three polyamines were obtained in axes, rather than in scutella. Seeds of low viability did not show putrescine increments after germination. It is suggested that spermidine and spermine are directly related to the germination process.     

Inhibition of seed germination by Macrophomina phaseolina is related to phaseolinone production

The production of phaseolinone, a phytotoxic metabolite of Macrophomina phaseolina in infected Phaseolus mungo seeds grown on soil, was estimated by enzyme-linked immunosorbent assay and HPLC. The degree of inhibition of seed germination correlated well with the amount of toxin produced; 50% inhibition was observed at a toxin level of 2.1 μg g^-1 of wet tissue. A comparison of the toxin-producing ability of nine isolates of the fungus obtained from different hosts and localities showed that the strain MPK'83 produced a significantly larger amount of the toxin, both in liquid culture and in infected seeds. The virulence of the isolates was related to their ability to produce phaseolinone.     

Hg浸种对玉米种子萌发过程中几种酶活性的影响

1　引　　言Hg是环境污染的重要因素,有关Hg对植物生长发育的影响及危害机制已有报导[1,3],但Hg对玉米种子萌发作用尚未见报道.种子萌发依靠自身储存的淀粉、脂肪和蛋白质的分解来提供物质和能量,合成新的生命物质.因此环境对种子萌发的影响首先表现在对这些大物质分解代谢的影     

Adenosine triphosphate content and seed vigor

ATP content in imbibed seeds is significantly correlated with seedling size in fatty, starchy and proteinaceous seeds, and it indicates viability in seed lots. ATP content thus appears to be a useful biochemical index of seed vigor.     

QTLs for early vigor of tropical maize

A strong photosynthetic performance and rapid leaf development, are important indicators of vigorous early growth. The aim of this study was to (1) evaluate the tropical maize (Zea mays L.) inbred lines CML444 and SC-Malawi for their photosynthetic performance at different growth stages and (2) assess quantitative trait loci (QTL) of photosynthesis-related traits in their 236 recombinant inbred lines at the heterotrophic growth stage. CML444 had a higher leaf chlorophyll (SPAD) content than SC-Malawi. Ten QTLs were found for the quantum efficiency of photosystem II (Φ_PSII; four), SPAD (three) and the specific leaf area (SLA; three). The relevance of seedling QTLs for Φ_PSII, SPAD and SLA for yield formation is emphasized by seven collocations (bins 5.01, 7.03, 8.05) with QTLs for kernel number and grain yield under field conditions. QTLs for SPAD at the V2 and at the reproductive stage did not collocate, indicating differences in the genetic control of SPAD at different growth stages. Knowing which loci affect SLA, SPAD and Φ_PSII simultaneously and which do not will help to optimize light harvest by the canopy.     

Identification and fine mapping of quantitative trait loci for seed vigor in germination and seedling establishment in rice

Seed vigor is an index of seed quality that is used to describe the rapid and uniform germination and the establishment of strong seedlings in any environmental conditions.Strong seed vigor in low-temperature germination conditions is particularly important in direct-sowing rice production systems. However, seed vigor has not been selected as an important breeding trait in traditional breeding programs due to its quantitative inherence. In this study, we identified and mapped eight quantitative trait loci(QTLs) for seed vigor by using a recombinant inbred population from a cross between rice(Oryza sativa L. ssp. indica) cultivars ZS97 and MH63.Conditional QTL analysis identified qSV-1, qSV-5b, qSV-6a, qSV-6b, and qSV-11 influenced seedling establishment and that qSV-5a, qSV-5c, and qSV-8 influenced only germination. Of these,qSV-1, qSV-5b, qSV-6a, qSV-6b, and qSV-8 were low-temperature-specific QTLs. Two major-effective QTLs, qSV-1, and qSV-5c were narrowed down to 1.13-Mbp and 400-kbp genomic regions, respectively. The results provide tightly linked DNA markers for the marker-assistant pyramiding of multiple positive alleles for increased seed vigor in both normal and low-temperature germination environments.     

The fluxes of H2O2 and O2 can be used to evaluate seed germination and vigor of Caragana korshinskii

Seed deterioration is detrimental to plant germplasm conservation, and predicting seed germination and vigor with reliability and sensitivity means is urgently needed for practical problems. We investigated the link between hydrogen peroxide (H₂O₂) flux, oxygen influx and seed vigor of Caragana korshinskii by the non-invasive micro-test technique (NMT). Some related physiological and biochemical changes in seeds were also determined to further explain the changes in the molecular fluxes. The results showed that there was a good linear relationship between germination and H₂O₂ flux, and that O₂ influx was more suitable for assessing seed vigor. H₂O₂ flux changed relatively little initially, mainly affected by antioxidants (APX, CAT and GSH) and H₂O₂ content; afterward, the efflux increased more and more rapidly due to high membrane permeability. With the damage of mitochondrial respiration and membrane integrity, O₂ influx was gradually reduced. We propose that monitoring H₂O₂ and O₂ fluxes by NMT may be a reliable and sensitive method to evaluate seed germination and vigor.     

Characterization of a maize beta-amylase cDNA clone and its expression during seed germination.

A maize (Zea mays L.) cDNA clone (pZMB2) encoding beta-amylase was isolated from a cDNA library prepared from the aleurone RNA of germinating kernels. The cDNA encodes a predicted product of 488 amino acids with significant similarity to known beta-amylases from barley (Hordeum vulgare), rye (Secale cereale), and rice (Oryza sativa). Glycine-rich repeats found in the carboxyl terminus of the endosperm-specific beta-amylase of barley and rye are absent from the maize gene product. The N-terminal sequence of the first 20 amino acids of a beta-amylase peptide derived from purified protein is identical to the 5th through 24th amino acids of the predicted cDNA product, indicating the absence of a conventional signal peptide in the maize protein. Recombinant inbred mapping data indicate that the cDNA clone is single-copy gene that maps to chromosome 7L at position 83 centimorgans. Northern blot analysis and in vitro translation-immunoprecipitation data indicate that the maize beta-amylase is synthesized de novo in the aleurone cells but not in the scutellum during seed germination.     

Cytological and physiological changes related to cryotolerance in orthodox maize embryos during seed development

Cytological and physiological changes were studied in orthodox maize (Zea mays L.) embryos following the acquisition of cryotolerance to liquid nitrogen during seed development. It was found that the embryonic cells at radicle portion were hydrated at all stages investigated, but those at early stages contained fully functional organelles, which disappeared at last developmental stages, and reserve materials accumulated intensively during seed development. Total soluble sugar content in the embryos had a steady rise on fresh weight and moisture weight basis; meanwhile, soluble and heat-stable proteins increased progressively in their number and contents as embryos matured. These cytological and biochemical changes had good correspondence with acquisition of cryotolerance in maize embryos.     

Excess boron reduces polyphenol oxidase activities in embryo and endosperm of maize seed during germination

The effects of increasing concentrations of boron (0, 0.1, 1, 10 and 20 mM) as boric acid on the rate of germination and polyphenol oxidase activities in embryo and endosperm tissues of maize seeds (Zea mays L. cv. Arifiye) were studied. The germination percentage of maize seeds was not affected by boron concentrations up to 10 mM, and decreased by 20 mM. Distilled water and lower boron concentrations (0.1 and 1 mM) increased polyphenol oxidase activities at the beginning of germination up to 12 h whereas its excess levels (10 and 20 mM) decreased polyphenol oxidase activities in embryos and endosperm during germination. Polyphenol oxidase activities with o-diphenolic substrates (caffeic acid, catechol and dopa) were found to be higher than with a monophenolic substrat (tyrosine) in both embryos and endosperms. Further, caffeic acid oxidizing polyphenol oxidase was found to show more activity in embryos of the seeds germinating in distilled water when compared to other substrates.