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PubMed1998

Enzymatic properties of endo-beta-N-acetylglucosaminidases from developing tomato fruits and soybean seeds: substrate specificity of plant origin endoglycosidase.

Substrate specificity and some other enzymatic properties of partial purified endo-beta-N-acetylglucosaminidases (endo-beta-GlcNAc-ase) from developing soybean seeds (Glycine max, Endo-GM) and developing tomato fruits (Lycopersicum esculentum, Endo-LE) were studied. The substrate specificity of these two endoglycosidases was explored and compared with regard to various pyridylaminated N-glycans derived from some naturally occurring glycoproteins. For Endo-GM and Endo-LE, several high mannose-type sugar chains bearing alpha 1-2 mannosyl residue(s), Man9-6GlcNAc2-PA (PA is pyridylamino) (80-100% relative hydrolysis), were most favored substrates followed by Man5GlcNAc2-PA (32% for Endo-LE, 43% for Endo-GM), a typical hybrid-type structure (GlcNAc1Man5GlcNAc2-PA; 34% for Endo-LE, 37% for Endo-GM), and then the common core pentasaccharide of N-glycan (Man3GlcNAc2-PA; 9% for Endo-GM and 16% for Endo-LE). On the contrary, both Endo-GM and Endo-LE could barely hydrolyze the xylose-containing N-glycans (Man3Xyl1GlcNAc2-PA, Man3Fuc1Xyl1GlcNAc2-PA) found ubiquitously in plant cells. The molecular mass of these two endoglycosidases was approximately 62 kDa by gel filtration and both Endo-GM and Endo-LE showed maximal activities for Man6GlcNAc2-PA in a weak acidic region (pH 6.0-6.5).

Hydrogen-Ion Concentration↗

PubMed2000

The African yam bean seed lectin affects the development of the cowpea weevil but does not affect the development of larvae of the legume pod borer.

Artificial feeding assays were used to study the effect of purified galactose-specific lectins from African yam beans (Sphenostylis stenocarpa) on development of larvae of the cowpea weevil, Callosobruchus maculatus (Coleoptera : Bruchidae) and the legume pod-borer, Maruca vitrata (Lepidoptera : Pyrialidae). Inhibition of development of C. maculatus was observed when larvae were fed on artificial cowpea seeds containing 0.2%, 2.0% and 5.0% (wt/wt) of dietary lectin. Larval mortality was between 30% and 88%, while delays in total developmental time ranged between 7 and 13 days. The lectin had no effect on development of larvae of M. vitrala, when tested through topical artificial diet incorporation assays, except at the extremely high dose of 35% dietary level.

Animals↗

PubMed1985

Primary cultures from defined brain areas; effects of seeding time on the development of beta-adrenergic- and dopamine-stimulated cAMP-activity during cultivation.

The influence of seeding time on the expression of beta-adrenergic- and dopamine-stimulated cAMP activity was studied in primary astroglial cultures from various brain areas. In all cultures isoproterenol (10(-7)-10(-5) M) caused an increased cAMP accumulation with time in culture. In brainstem cultures from 17-day-old embryos there was a decreased intracellular cAMP accumulation between 3 and 4 weeks. In all newborn rats and in striatal cultures from 7-day-postnatal rats there was a similar decrease between 2 and 3 weeks. These changes are discussed and interpreted as a differentiation of the cells concerning beta-receptors. The most prominent cAMP accumulation caused by isoproterenol was found in striatal cultures from newborn rat. Although isoproterenol and noradrenaline both caused intracellular cAMP accumulation, isoproterenol was the most effective. There was a cAMP accumulation specific to dopamine (10(-6)-10(-4)M) in 2-week-old striatal cultures from newborn rat, although there was an interaction with beta-adrenergic receptors. In the other cultures studied there was only a very small dopamine stimulation of cAMP. The expression of this heterogeneity among astroglial primary cultures from various brain areas seems to be influenced by the genetic program for cellular maturation and by specific cellular contacts in vivo until seeding and in culture.

Animals↗

PubMed1968

Fate of radioactive gibberellin a(1) in maturing and germinating seeds of peas and Japanese morning glory.

Radioactive gibberellin A(1) ((3)H-GA(1)) was injected into excised fruits of peas and Japanese morning glory. These were then grown in sterile culture to maturity and the label was followed in the seeds during further development and subsequent germination. During development of both pea and morning-glory seeds a large part of the radioactivity became associated with the aqueous fraction, while another part of the (3)H-GA(1) was converted into 2 new, acidic, biologically active compounds, designated X(1) and X(2). A relatively small part of the neutral compounds could be converted back to (3)H-GA(1), X(1), and X(2) by means of mild acid hydrolysis. During germination of pea and morning-glory seeds, part of the bound compounds was released in the form of (3)H-GA(1), X(1) and X(2) while, particularly during rapid seedling growth, a further conversion of (3)H-GA(1), mainly to X(1), took place. In pea seedlings, growth during the first 2 to 3 days after imbibition was not affected by Amo-1618, an inhibitor of gibberellin biosynthesis. This, in conjunction with the findings on the interconversions between free and bound (3)H-GA(1) suggests that, at least in peas, early seedling growth may at least partly be regulated by gibberellins released from a bound form which was formed during seed development.

Journal Article↗

PubMed2001

Isolation and characterization of mutants defective in seed coat mucilage secretory cell development in Arabidopsis.

In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.

Arabidopsis↗

PubMed2003

Molecular dissection of a dormancy QTL region near the chromosome 7 (5H) L telomere in barley.

Moderate seed dormancy is desirable in barley (Hordeum vulgare L.). It is difficult for breeders to manipulate seed dormancy in practical breeding programs because of complex inheritance and large environmental effects. Quantitative trait locus (QTL) mapping opens a way for breeders to manipulate quantitative trait genes. A seed dormancy QTL, SD2, was mapped previously in an 8-cM interval near the chromosome 7 (5H) L telomere from a cross of 'Steptoe' (dormant)/'Morex' (non-dormant) by the North American Barley Genome Project using an interval mapping method and a relatively low-resolution genetic map. SD2 has a moderate dormancy effect, which makes it a promising candidate gene for moderate seed dormancy in barley cultivar development. The fine mapping of SD2 is required for efficient manipulation of SD2 in breeding and would facilitate the study of dormancy in barley. Ten different Morex isolines were generated, including regenerated Morex, of which nine lines had duplicates. The isolines together with Steptoe and Morex were grown in growth room and field environments for 2 years (2000 and 2001). In the growth room, relatively low growing temperatures (25 degrees C day/15 degrees C night) were employed to promote seed dormancy development. Seed germination percentage, determined at different post-harvest after-ripening periods, was used to measure seed dormancy. Fine mapping using the substitution mapping method based on differences among isolines resolved the SD2 QTL into an 0.8-cM interval between molecular markers MWG851D and MWG851B near the chromosome 7 (5H) L telomere. Relatively low temperatures (< or =25 degrees C) during seed development promoted the expression of the SD2 dormancy QTL. The chromosome region above the MWG851D-MWG851B interval might play a role in reducing barley seed dormancy during after-ripening.

Chromosome Mapping↗

PubMed1985

The acylation of sn-glycerol 3-phosphate and the metabolism of phosphatidate in microsomal preparations from the developing cotyledons of safflower (Carthamus tinctorius L.) seed.

Microsomal preparations from the developing cotyledons of safflower (Carthamus tinctorius) catalysed the acylation of sn-glycerol 3-phosphate in the presence of acyl-CoA. The resulting phosphatidate was further utilized in the synthesis of diacyl- and tri-acylglycerol by the reactions of the so-called 'Kennedy pathway' [Kennedy (1961) Fed. Proc. Fed. Am. Soc. Exp. Biol. 20, 934-940]. Diacylglycerol equilibrated with the phosphatidylcholine pool when glycerol backbone, with the associated acyl groups, flowed from phosphatidate to triacylglycerol. The formation of diacylglycerol from phosphatidate through the action of a phosphatidate phosphohydrolase (phosphatidase) was substantially inhibited by EDTA and, under these conditions, phosphatidate accumulated in the microsomal membranes. The inhibition of the phosphatidase by EDTA was alleviated by Mg2+. The presence of Mg2+ in all incubation mixtures stimulated quite considerably the synthesis of triacylglycerol in vitro. Microsomal preparations incubated with acyl-CoA, sn-glycerol 3-phosphate and EDTA synthesized sufficient phosphatidate for the reliable analysis of its intramolecular fatty acid distribution. In the presence of mixed acyl-CoA substrates the sn-glycerol 3-phosphate was acylated exclusively in position 1 with the saturated fatty acids, palmitate and stearate. The polyunsaturated fatty acid linoleate was, however, utilized largely in the acylation of position 2 of sn-glycerol 3-phosphate. The affinity of the enzymes involved in the acylation of positions 1 and 2 of sn-glycerol 3-phosphate for specific species of acyl-CoA therefore governs the non-random distribution of the different acyl groups in the seed triacylglycerols. The acylation of sn-glycerol 3-phosphate in position 1 with saturated acyl components also accounts for the presence of these groups in position 1 of sn-phosphatidylcholine through the equilibration of diacylglycerol with the phosphatidylcholine pool, which occurs when phosphatidate is utilized in the synthesis of triacylglycerol. These results add further credence to our previous proposals for the regulation of the acyl quality of the triacylglycerols that accumulate in developing oil seeds [Stymne & Stobart (1984) Biochem. J. 220, 481-488; Stobart & Stymne (1985) Planta 163, 119-125].

Acyl Coenzyme A↗

PubMed1995

Development of fibroblast-seeded ligament analogs for ACL reconstruction.

We fabricated "ligament analogs" in vitro by seeding high-strength resorbable collagen fiber scaffolds with intraarticular (anterior cruciate ligament, ACL) or extraarticular (patellar tendon, PT) rabbit fibroblasts. Fibroblasts attached, proliferated, and secreted new collagen on the ligament analogs in vitro. Fibroblast function depended on the tissue culture substrate (ligament analog vs. tissue culture plate) and the origin of the fibroblasts (ACL vs. PT) PT fibroblasts proliferated more rapidly than ACL fibroblasts when cultured on ligament analogs. Collagen synthesis by ACL and PT fibroblasts was approximately tenfold greater on ligament analogs than on tissue culture plates. The composition, structure, and geometry of the collagen fiber scaffolds may promote collagen synthesis within ligament analogs in vitro. Ligament analogs roughly approximate the structure and strength of native ligament tissue. Ongoing in vivo studies suggest that autogenous fibroblast-seeded ligament analogs remain viable after implantation into the knee joint. With further development, ligament analogs may be useful as implants for ACL reconstruction surgery.

Animals↗

PubMed1994

Characterisation of cDNA and genomic clones encoding homologues of the 65 kDa regulatory subunit of protein phosphatase 2A in Arabidopsis thaliana.

Two cDNA species encoding sequences homologous to the 65 kDa regulatory subunit (PR 65) of protein phosphatase 2A (PP2A) have been isolated from an Arabidopsis thaliana cDNA library. These were designated pDF1 and pDF2. pDF1 is 1795 bp long and by comparison with the human and porcine PP2A regulatory subunit sequences represents a full-length clone. It encodes a predicted polypeptide of 587 amino acid residues. pDF2 is truncated at the 5' end by 237 bp. The complete nucleotide sequences have been determined for both cDNA species. Comparison of the nucleotide and the deduced amino acid sequences showed that the two sequences were homologous but not identical and therefore must be derived from two different genes. Northern blot analysis was performed on total RNA and poly(A)+ RNA isolated from seed at various stages of development and from young leaf material of Brassica napus L. (oilseed rape). Both cDNA probes hybridised to a single major mRNA species of ca. 2.2 kb. The highest level of expression was observed in the total RNA from developing rape seed at about 33 days after flowering, and the transcript level in the poly(A)+ RNA of the seed was higher than in young leaf of oilseed rape. Southern blot analysis was performed on two varieties of A. thaliana and B. napus genomic DNA; this identified a small family of genes in A. thaliana consisting of at least 2 or 3 members and a larger multigene family in B. napus of at least 5 or 6 members. Two independent genomic clones were isolated from an A. thaliana genomic library. Sequencing of a fragment common to both revealed that the sequence was identical in both clones and, therefore, they were assumed to contain the same genomic sequence. The genomic sequence selected, designated regA, is 3639 bp long and the coding sequence contains eleven introns. The gene encodes a predicted polypeptide of 590 amino acid residues. The sequence comparison with both cDNA sequences showed that it is homologous but not identical to the two, confirming that at least three different genes exist in A. thaliana which encode PR65 of PP2A.

Amino Acid Sequence↗

PubMed1999

Seed abortion in Pongamia pinnata (Fabaceae).

In Pongamia pinnata only one of the two ovules develops into a seed in most of the pods. Since pollen was not found to be limiting and reduced fertilization could not completely explain the observed frequency of seed abortion, it implied an effect of postfertilization factors. Aqueous extracts of developing seeds and maternal tissue (placenta) did not influence abortion in vitro, suggesting that abortion may not be mediated by a chemical. Experimental uptake of (14)C sucrose in vitro indicated that both the stigmatic and the peduncular seed have similar inherent capacities of drawing resources, but the peduncular seed is deprived of resources in the presence of the stigmatic seed. This deprivation of the peduncular seed could be offset by supplying an excess of hormones leading to the subsequent formation of two seeds in a pod. The prevalence of single-seeded pods in P. pinnata seems therefore to be a result of competition between the two seeds for maternal resources. The evolutionary significance of single-seeded pods in P. pinnata is discussed with respect to possible dispersal advantage enjoyed by such pods.

Journal Article↗

PubMed2005

Elevated temperature during reproductive development affects cone traits and progeny performance in Picea glauca x engelmannii complex.

Two temperature regimes were applied during reproductive development of seed and pollen cones of interior spruce (Picea glauca (Moench) Voss and Picea engelmannii (Parry) complex) to determine temperature effects on the adaptive traits of progeny. In Experiment 1, identical crosses were made on potted interior spruce using untreated pollen followed by exposure to a day/night temperature of 22/8 or 14/8 degrees C with a 12-h photoperiod during the stages of reproductive development from post-pollination to early embryo development. Frost hardiness and growth of progeny from seed produced in the two temperature treatments were measured over a 4-year period. Elevated temperature significantly affected both seed-cone development and the adaptive properties of the progeny. Seed cones exposed to the 22/8 degrees C treatment reached the early embryo stage in 53 days versus 92 days in the 14/8 degrees C treatment. Seed yields, cotyledon emergence and percent germination were also significantly enhanced by the 22/8 degrees C treatment. Progeny from seed produced in the higher temperature treatment showed significantly reduced spring and fall frost hardiness, but the elevated temperature treatment had no significant effects on time of bud burst, growth patterns or final heights. In Experiment 2, single ramets of the same clone were subjected to a day/night temperature of 20/8 or 10/8 degrees C during pollen cone development, starting from meiosis and ending at pollen shedding. The two populations of pollen were then crossed with untreated seed cones. Compared with pollen cones exposed to the 10/8 degrees C treatment, pollen cones exposed to the 20/8 degrees C treatment during development reached the shedding stage 2-4 weeks earlier, whereas pollen yields, in vitro viability and fertility (seed set) were significantly lower; however, the resulting progeny displayed no treatment differences in frost hardiness or growth after 1 year. Results suggest that seed orchard after-effects could be caused by temperature differences between orchard site and parent tree origin and that this effect acts on maternal development. Gametophytic (pollen or megagametophyte or both) and early embryo (sporophytic) selection are possible mechanisms that may explain the observed results. Although the effects are biologically significant, they are relatively small and do not justify changes in current deployment strategies for seed orchard seed.

Hot Temperature↗

PubMed2006

Involvement of AtLAC15 in lignin synthesis in seeds and in root elongation of Arabidopsis.

Laccase, EC 1.10.3.2 or p-diphenol:dioxygen oxidoreductase, has been proposed to be involved in lignin synthesis in plants based on its in vitro enzymatic activity and a close correlation with the lignification process in plants. Despite many years of research, genetic evidence for the role of laccase in lignin synthesis is still missing. By screening mutants available for the annotated laccase gene family in Arabidopsis, we identified two mutants for a single laccase gene, AtLAC15 (At5g48100) with a pale brown or yellow seed coat which resembled the transparent testa (tt) mutant phenotype. A chemical component analysis revealed that the mutant seeds had nearly a 30% decrease in extractable lignin content and a 59% increase in soluble proanthocyanidin or condensed tannin compared with wild-type seeds. In an in vitro enzyme assay, the developing mutant seeds showed a significant reduction in polymerization activity of coniferyl alcohol in the absence of H(2)O(2). Among the dimers formed in the in vitro assay using developing wild-type seeds, 23% of the linkages were beta-O-4 which resembles the major linkages formed in native lignin. The evidence strongly supports that AtLAC15 is involved in lignin synthesis in plants. To our knowledge, this is the first genetic evidence for the role of laccase in lignin synthesis. Changes in seed coat permeability, seed germination and root elongation were also observed in the mutant.

Arabidopsis↗

PubMed1992

[The relation between the seed germination and seedling development of Bletilla striata and Mycena osmundicola etc. fungi].

This paper reports the effects of Mycena osmundicola etc. fungi on the seed germination and seedling growth of Bletilla striata. The results showed that B. striata seeds are easily germinated under normal conditions and belong to a special type among Orchidaceae. Fungi promote cotyledon differentiation and growth, as well as rhizoid formation of B. striata protocorms after seeds are sown with fungi. A liquid extract mixture enhanced the percentage of seed germination, and carbinol extract notably accelerated differentiation and growth of the protocorm's cotyledon after seeds were incubated with the liquid extract of Mycena osmundicola-culture products.

Agaricales↗

PubMed1994

Hormonal and environmental responsiveness of a developmentally regulated protein repair L-isoaspartyl methyltransferase in wheat.

The L-isoaspartyl protein methyltransferase (EC 2.1.1.77) has been proposed to be involved in the repair of spontaneously damaged proteins by facilitating the conversion of abnormal L-isoaspartyl residues to normal L-aspartyl residues. Based on the abundance of this enzyme in the seeds of a variety of plants and its unique substrate specificity, it has been hypothesized that it functions to prevent the accumulation of abnormal aspartyl residues in the proteins of aging seeds that can limit the viability of the embryo or its chances for germination. In this work, we show that the expression of the L-isoaspartyl methyltransferase is under developmental regulation in the winter wheat, Triticum aestivum. Methyltransferase mRNA and active enzyme are first detected in seeds during the late stages (III-IV) of caryopsis development. As mature seeds germinate, methyltransferase mRNA levels decline and are nearly undetectable by 72 h post-imbibition. Enzyme activity remains constant for 24 h post-imbibition and then decreases rapidly following the reduction of its corresponding mRNA. Methyltransferase activity is very low or undetectable in wheat seedlings, including leaf and root tissues. We show, however, that the L-isoaspartyl methyltransferase can be induced in vegetative tissues in response to hormone treatment and environmental stress. Abscisic acid, a phytohormone involved in seed development and desiccation tolerance, induces both methyltransferase mRNA and enzyme activity in 4-day-old wheat seedlings. Dehydration and salt stress also induce its transcription and enzymatic activity in seedlings. The ability of a plant to regulate methyltransferase activity in its seeds and vegetative tissues in response to desiccation, aging, and environmental stress may allow the plant to efficiently repair protein damage associated with these physiological changes.

Abscisic Acid↗

PubMed2002

Seed-specific overexpression of a potato sucrose transporter increases sucrose uptake and growth rates of developing pea cotyledons.

During the storage phase, cotyledons of developing pea seeds are nourished by nutrients released to the seed apoplasm by their maternal seed coats. Sucrose is transported into pea cotyledons by sucrose/H+ symport mediated by PsSUT1 and possibly other sucrose symporters. PsSUT1 is principally localised to plasma membranes of cotyledon epidermal and subepidermal transfer cells abutting the seed coat. We tested the hypothesis that endogenous sucrose/H+ symporter(s) regulate sucrose import into developing pea cotyledons. This was done by supplementing their transport activity with a potato sucrose symporter (StSUT1), selectively expressed in cotyledon storage parenchyma cells under control of a vicilin promoter. In segregating transgenic lines, enhanced [(14)C]sucrose influx into cotyledons above wild-type levels was found to be dependent on StSUT1 expression. The transgene significantly increased (approximately 2-fold) transport activity of cotyledon storage parenchyma tissues where it was selectively expressed. In contrast, sucrose influx into whole cotyledons through the endogenous epidermal transfer cell pathway was increased by only 23% in cotyledons expressing the transgene. A similar response was found for rates of biomass gain by intact cotyledons and by excised cotyledons cultured on a sucrose medium. These observations demonstrate that transport activities of sucrose symporters influence cotyledon growth rates. The attenuated effect of StSUT1 overexpression on sucrose and dry matter fluxes by whole cotyledons is consistent with a large proportion of sucrose being taken up at the cotyledonary surface. This indicates that the cellular location of sucrose transporter activity plays a key role in determining rates of sucrose import into cotyledons.

Biological Transport↗

PubMed2005

Arabidopsis cytokinin receptor mutants reveal functions in shoot growth, leaf senescence, seed size, germination, root development, and cytokinin metabolism.

We used loss-of-function mutants to study three Arabidopsis thaliana sensor histidine kinases, AHK2, AHK3, and CRE1/AHK4, known to be cytokinin receptors. Mutant seeds had more rapid germination, reduced requirement for light, and decreased far-red light sensitivity, unraveling cytokinin functions in seed germination control. Triple mutant seeds were more than twice as large as wild-type seeds. Genetic analysis indicated a cytokinin-dependent endospermal and/or maternal control of embryo size. Unchanged red light sensitivity of mutant hypocotyl elongation suggests that previously reported modulation of red light signaling by A-type response regulators may not depend on cytokinin. Combined loss of AHK2 and AHK3 led to the most prominent changes during vegetative development. Leaves of ahk2 ahk3 mutants formed fewer cells, had reduced chlorophyll content, and lacked the cytokinin-dependent inhibition of dark-induced chlorophyll loss, indicating a prominent role of AHK2 and, particularly, AHK3 in the control of leaf development. ahk2 ahk3 double mutants developed a strongly enhanced root system through faster growth of the primary root and, more importantly, increased branching. This result supports a negative regulatory role for cytokinin in root growth regulation. Increased cytokinin content of receptor mutants indicates a homeostatic control of steady state cytokinin levels through signaling. Together, the analyses reveal partially redundant functions of the cytokinin receptors and prominent roles for the AHK2/AHK3 receptor combination in quantitative control of organ growth in plants, with opposite regulatory functions in roots and shoots.

Alleles↗

PubMed2004

Characterization of soluble and putative membrane-bound UDP-glucuronic acid decarboxylase (OsUXS) isoforms in rice.

Arabinoxylans in crop plants are the major sugar components of the cell walls, and UDP-xylose is a key substrate in the biosynthesis of xylans. In this study, the six putative UDP-D-glucuronic acid decarboxylase genes from rice (Oryza sativa UDP-xylose synthase; OsUXS) were cloned. Except for the soluble form of OsUXS3 (GenBank Accession No. \AB079064), the remaining five OsUXS enzymes contain a putative membrane-bound region. The six OsUXS genes were classified into three types by phylogenetic analysis and were expressed during the development of rice seeds. The HPLC retention times of the enzyme products and NMR data, indicate that the recombinant OsUXS2 enzyme catalyzes the conversion of UDP-D-glucuronic acid to UDP-D-xylose. Interestingly, the reactions catalyzed by the recombinant OsUXS2 and OsUXS3 enzymes were inhibited by NADP+, and accelerated by NADPH. The catalytic activities of the recombinant OsUXS2 and OsUXS3 enzymes were strongly inhibited by UDP, UTP, TDP, and TTP. The expression levels of OsUXS genes changed in different manners during the development of rice seeds, suggesting that each corresponding OsUXS enzyme plays a significant role in rice seed development at a certain stage. In the present study, we report that the UXS2-type enzyme of rice is not only characterized for the first time but also show significant findings involved in the gene expression of OsUXSs.

Amino Acid Motifs↗

PubMed2004

Complex combination of seed dormancy and seedling development determine emergence of Viburnum tinus (Caprifoliaceae).

BACKGROUND AND AIMS: The shrub Viburnum tinus is widely distributed in mattoral vegetation of the Mediterranean basin. The purpose of the present study was to classify the seed dormancy type and examine the requirements for embryo growth, root protrusion and shoot emergence. METHODS: Overwintered fruits were collected in western Spain in April 2001 and prepared in three ways: entire pericarp was removed, exocarp and mesocarp were removed or fruits were left intact. Fruits treated in these three ways were subjected to artificial annual temperature cycles or to constant temperature regimes for 1.5 years. KEY RESULTS: Removal of exocarp and mesocarp was necessary for embryo growth and germination. High temperature favoured dormancy alleviation and embryo growth, intermediate to low temperatures favoured root protrusion, and intermediate temperature shoot emergence. There was substantial germination at constant temperature regimes, indicating an overlap between temperature intervals suitable for the different stages of embryo and seedling development. Functionally, V. tinus has the same root and shoot emergence pattern that is described for other Viburnum species considered to have epicotyl dormancy. However, the requirement for high and low temperatures for radicle protrusion and epicotyl emergence, respectively, was missing in V. tinus; these characters are the foundation for the epicotyl dormancy classification. CONCLUSIONS: It is concluded that V. tinus does not have epicotyl dormancy. Instead, there is a combination of a weak morphophysiological dormancy and a slow germination process, where different temperatures during an annual cycle favour different development stages. The present study suggests that the first complete seedlings would emerge in the field 1.5 years after fruit maturation in October, i.e. seed dispersal during winter, embryo growth during the first summer, root protrusion and establishment during the second autumn and winter, and cotyledon emergence during the second spring.

Germination↗