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PubMed1989

Productivity and food value of Amaranthus cruentus under non-lethal salt stress.

Stress effects from the accumulation of metal salts may pose a problem for plants in closed biological systems such as spacecraft. This work examined the effects of salinity on growth, photosynthesis and carbon allocation in the crop plant, Amaranthus. Plants were germinated and grown in modified Hoagland's solution with NaCl concentrations of 0 to 1.0%. Plants received salt treatments at various times in development to assess effects on particular life history phases. For Amaranthus cruentus, germination, vegetative growth, flowering, seed development and yield were normal at salinities from 0 to 0.2%. Inhibition of these phases increased from 0.2 to 0.4% salinity and was total above 0.5%. 1.0% salinity was lethal to all developmental phases. Onset of growth phases were not affected by salinity. Plants could not be adapted by gradually increasing salinity over days or weeks. Water uptake increased, while photosynthetic CO2 uptake decreased with increasing salinity on a dry weight basis during vegetative growth. Respiration was not affected by salinity. After flowering, respiration and photosynthesis decreased markedly, such that 1.0% NaCl inhibited photosynthesis completely. Protein levels were unchanged with increasing salinity. Leaf starch levels were lower at salinities of 0.5% and above, while stem starch levels were not affected by these salinities. The evidence supports salt inhibition arising from changes in primary biochemical processes rather than from effects on water relations. While not addressing the toxic effects of specific ions, it suggests that moderate salinity per se need not be a problem in space systems.

Ecological Systems, Closed↗
PubMed2006

ABI3 expression ceases following, but not during, germination of tomato and Arabidopsis seeds.

In many plant species, including tomato and Arabidopsis, the inception of dormancy during seed development is mediated by abscisic acid (ABA) and the transcription factor ABSCISIC ACID INSENSITIVE3/VIVIPAROUS1 (ABI3/VP1). Consequently, seeds carrying mutations in this gene germinate precociously. The ABI3 orthologue isolated from tomato (LeABI3) is a single copy gene expressed only in seeds. ABI3 expression ceases following the completion of germination in both tomato and Arabidopsis seeds, suggesting that expression of this gene does not regulate germination. LeABI3 expression in tomato wild-type embryos, while present in intact seeds, is greater than in their isolated embryo axes. Decreased LeABI3 expression does not occur in isolated axes from the gibberellin (GA)-deficient gib-1 mutant of tomato, in contrast to embryos from the intact seeds. This is indicative of a signal passing from the endosperm to the embryo which acts to promote LeABI3 expression in the latter, and that this signal is GA or GA-derived.

Arabidopsis↗
PubMed2004

The relation of starch phosphorylases to starch metabolism in wheat.

Tissues of wheat (Triticum aestivum L., var. Star) exhibit three starch phosphorylase activity forms resolved by non-denaturing polyacrylamide gel affinity electrophoresis (P1, P2 and P3). Compartmentation analysis of young leaf tissues showed that P3 is plastidic, whereas P1 and P2 are cytosolic. P1 exhibits a strong binding affinity to immobilized glycogen upon electrophoresis, whereas P2 and the chloroplastic P3 do not. Cytosolic leaf phosphorylase was purified to homogeneity by affinity chromatography. The single polypeptide product constituted both the P1 and P2 activity forms. Probes for the detection of phosphorylase transcripts were derived from cDNA sequences of cytosolic and plastidic phosphorylases, and these-together with activity assays and a cytosolic phosphorylase-specific antiserum-were used to monitor phosphorylase expression in leaves and seeds. Mature leaves contained only plastidic phosphorylase, which was also strongly evident in the endosperm of developing seeds at the onset of reserve starch accumulation. Germinating seeds contained only cytosolic phosphorylase, which was restricted to the embryo. Plastidic phosphorylase thus appears to be associated with transitory leaf starch metabolism and with the initiation of seed endosperm reserve starch accumulation, but it plays no role in the degradation of the reserve starch. Cytosolic phosphorylase may be involved in the processing of incoming carbohydrate during rapid tissue growth.

Amino Acid Sequence↗
PubMed2000

Unfertilized ovules of Epilobium obcordatum (Onagraceae) continue to grow in developing fruits.

To determine whether unfertilized ovules continue to grow when in an ovary containing fertilized ovules, we measured ovule lengths in developing fruits of Epilobium obcordatum that were harvested 4, 5, 8, and 10 d post pollination. We found that unfertilized ovules that were in the presence of fertilized ovules continued to grow and that there was a broad range of overlap in their sizes at all sampling times. This effect was found for two types of unfertilized ovules that occur throughout the length of the ovary: normal, unfertilized ovules, apparently bypassed by pollen tubes; and sterile ovules lacking an embryo sac. In addition, there is a position effect within developing fruits. Both fertilized and unfertilized ovules are larger at the stylar end. In six samples resulting from pollination with a single pollen tetrad, a total of 18 embryos were found, and the effect on unfertilized ovules, greatest at the stylar end, diminished with distance from the ovules with embryos. Our results are consistent with the interpretation that diffusible hormones produced by developing seeds cause nearby unfertilized ovules to grow. We conclude that caution is necessary when attempting to infer ovule fertilization histories from the appearances of ovules in developing and mature fruits. What are often inferred to be aborted seeds, in many cases, may not be seeds at all. They may be enlarged, unfertilized ovules.

Journal Article↗
PubMed2006

Mendelian segregation for two-factor apomixis in Erigeron annuus (Asteraceae).

The inheritance of asexual seed development (apomixis) in Erigeron annuus (Asteraceae) was evaluated in a triploid (2n=3x=27) population resulting from a cross between an apomictic tetraploid (2n=4x=36) pollen parent and a sexual diploid (2n=2x=18) seed parent. Diplospory (unreduced female gametophyte formation) and autonomous development (embryo and endosperm together) segregated independently in the population yielding four distinct phenotype classes: (1) apomictic plants combining diplospory and autonomous development, (2) diplosporous plants lacking autonomous development, (3) meiotic plants with autonomous (though abortive) development and (4) meiotic plants lacking autonomous development. Each class was represented by approximately one-quarter of the population (n=117), thus corresponding to a two-factor genetic model with no linkage (chi(2)=2.59, P=0.11). Observations demonstrate that autonomous embryo and endosperm development (jointly) may occur in either reduced or unreduced egg cells. The cosegregation of the traits is attributed to tight linkage or pleiotropy. The data are consistent with the hypothesis that autonomous development in E. annuus is regulated by a single fertilization factor, F, which initiates development of both the embryo and the endosperm in the absence of fertilization.

Crosses, Genetic↗
PubMed2001

The poplar bark storage protein gene (Bspa) promoter is responsive to photoperiod and nitrogen in transgenic poplar and active in floral tissues, immature seeds and germinating seeds of transgenic tobacco.

In Populus, seasonal nitrogen storage involves the accumulation of a 32 kDa bark storage protein (BSP) in the inner bark parenchyma and xylem rays. Poplar BSPs are encoded by a multigene family and one member, bspA, has been cloned and sequenced. The regulation of bspA was investigated by transforming either hybrid poplar or tobacco with a chimeric gene consisting of the 2.8 kb bspA promoter fused to the coding region of beta-glucuronidase (uidA). In transformed poplar, the bspA 2.8 kb promoter conferred both short-day (SD) and nitrogen (N) inducibility to GUS and activity was localized to the bark (primary and secondary phloem, and cortex) and xylem rays. Night-break treatments inhibited SD induction of GUS. Deletion of the 1.6 kb distal DNA sequences from the bspA promoter eliminated SD induction of GUS while some N induction was retained. These results indicate that although poplar BSP is encoded by a multigene family, transcriptional activation of bspA per se can account for bsp expression in bark and xylem rays in response to either SD or N treatment. These results also show that the elements responsible for SD or N induction are separable. Because of the long generation intervals associated with trees, the developmental regulation of bspA in flowers, developing seeds, and germinating seeds was investigated by transforming the 2.8 kb bspA-promoter::uidA chimeric gene into tobacco. The bspA promoter was active in developing tobacco floral tissues and in seeds during early stages of embryogenesis, decreased progressively during seed maturation and regained activity upon seed germination. Although seed storage proteins of poplar share some similarities to poplar BSP, the observed developmental expression patterns in tobacco are consistent with a role for bspA in vegetative rather than seed storage protein storage.

Gene Expression Regulation, Developmental↗
PubMed1976

Glycoprotein Metabolism in the Cotyledons of Pisum sativum during Development and Germination.

The glycoprotein nature of legumin and vicilin, the reserve globulins in the cotyledons of Pisum sativum was studied. Legumin from mature seed was found to contain 1% neutral sugars (mannose and glucose) and 0.1% amino sugar (glucosamine), whereas vicilin contained 0.3% neutral sugar (mannose) and 0.2% amino sugar (glucosamine). On the basis of the incorporation of (14)C-labeled glucosamine, it appeared that not all of the component subunits of the reserve proteins are glycosylated to the same extent. In addition, it has been established that glycosylation occurs after peptide synthesis. During seed development there was a change in neutral sugars and amino sugar ratio in vicilin. During germination, the neutral sugars and the amino sugar content of the glycoproteins declined. These findings are discussed in relation to the synthesis and degradation of the glycosyl component of the glycoproteins.

Journal Article↗
PubMed1985

Accumulation and Subcellular Localization of alpha-Galactosidase-Hemagglutinin in Developing Soybean Cotyledons.

We have investigated the accumulation and intracellular localization of soybean (Glycine max [L.] Merr. cv Forrest) alpha-galactosidase-hemagglutinin during seed development. Cotyledon tissue was embedded in Lowicryl K4M and immunocytochemical localization was accomplished through treating thin sections with alpha-galactosidase antisera followed by indirect labeling with protein A coupled to colloidal gold. Gold particles were localized on the Golgi apparatus and protein bodies. We interpret this to indicate that alpha-galactosidase-hemagglutinin is transferred to and transported through the Golgi apparatus and finally deposited within the protein body by a Golgi apparatus-mediated process.

Journal Article↗
PubMed2006

Methodological improvements on extraction of nuclear proteins and its preliminary analysis during the maize (Zea mays L.) endosperm development.

A procedure to obtain endosperm protein extracts was standardized. After confirming the enrichment with nuclear proteins by immunodetection, the protein profiles of extracts from different seed development stages were compared by SDS-PAGE that showed the existence of several differentially expressed proteins.

Electrophoresis, Polyacrylamide Gel↗
PubMed1989

Enhancement of the methionine content of seed proteins by the expression of a chimeric gene encoding a methionine-rich protein in transgenic plants.

We have constructed a chimeric gene encoding a Brazil nut methionine-rich seed protein which contains 18% methionine. This gene has been transferred to tobacco and expressed in the developing seeds. Tobacco seeds are able to process the methionine-rich protein efficiently from a larger precursor polypeptide of 17 kDa to the 9 kDa and 3 kDa subunits of the mature protein, a procedure which involves three proteolytic cleavage steps in the Brazil nut seed. The accumulation of the methionine-rich protein in the seeds of tobacco results in a significant increase (30%) in the levels of the methionine in the seed proteins of the transgenic plants. Our data indicate that the introduction of a chimeric gene encoding a methionine-rich seed protein into crop plants, particularly legumes whose seeds are deficient in the essential sulfur-containing amino acids, represents a feasible method for improving the nutritional quality of seed proteins.

Amino Acids↗
PubMed2006

Identification of quantitative trait loci for ABA sensitivity at seed germination and seedling stages in rice.

Abscisic acid (ABA) is one of the important plant hormones, which plays a critical role in seed development and adaptation to abiotic stresses. The sensitivity of rice (Oryza sativa L.) to exogenous ABA at seed germination and seedling stages was investigated in the recombinant inbred line (RIL) population derived from a cross between irrigated rice Zhenshan 97 and upland rice IRAT109, using relative germination vigor (RGV), relative germination rate (RGR) and leaf rolling scores of spraying (LRS) or culturing (LRC) with ABA as sensitivity indexes. The phenotypic correlation analysis revealed that only RGV at germination stage was positively correlated to ABA sensitivity at seedling stage. QTL detection using composite interval mapping (CIM) and mixed linear model was conducted to dissect the genetic basis of ABA sensitivity, and the single-locus QTLs detected by both methods are in good agreement with each other. Five single QTLs and six pairs of epistatic QTLs were detected for ABA sensitivity at germination stage. Eight single QTLs and five pairs of epistatic QTLs were detected for ABA sensitivity at seedling stage. Two QTLs were common between LRS and LRC; and one common QTL was detected for RGV, LRS and LRC simultaneously. These results indicated that both single and epistatic loci were involved in the ABA sensitivity in rice, and the genetic basis of ABA sensitivity at seed germination and seedling stage was largely different.

Abscisic Acid↗
PubMed2005

Perfect syncarpy in apple (Malus x domestica 'Summerland McIntosh') and its implications for pollination, seed distribution and fruit production (Rosaceae: Maloideae).

BACKGROUND AND AIMS: The gynoecium of the domestic apple, Malus x domestica, has been assumed to be imperfectly syncarpic, whereby pollination of each stigmatic surface can result in fertilization within only one of the five carpels. Despite its implied effect on fruit quantity and quality, the resulting influence of flower form on seed set and distribution within the apple fruit has seldom been investigated. Instead, poor fruit quality is usually attributed to problems with pollination, such as low bee numbers and/or ineffective pollinators within apple agro-ecosystems. The objective of this study was to determine the true nature of gynoecial structure and its influence on fruit production in the apple cultivar 'Summerland McIntosh'. METHODS: A stigma-excision method was used to determine the effects of uneven pollination among the five stigmas on fruit quantity (as measured by fruit set), and quality (seed number and distribution). In addition, flowers were examined microscopically to determine pollen tube pathways. KEY RESULTS: Fruit set, seed number, seed distribution, and the microscopic examination of flower gynoecial structure reported in this study indicated that the gynoecium of the cultivar Summerland McIntosh is perfectly syncarpic and not imperfectly syncarpic as previously thought. CONCLUSIONS: Pollination levels among the five stigmas need not be uniform to obtain full seed development within Summerland McIntosh fruit; even if one stigmatic surface is adequately pollinated, a full complement of seeds is likely. The importance of perfect syncarpy in recognizing true causes of poor fruit quality in apple is discussed.

Crosses, Genetic↗
PubMed2006

Genes directly regulated by LEAFY COTYLEDON2 provide insight into the control of embryo maturation and somatic embryogenesis.

The B3 domain protein LEAFY COTYLEDON2 (LEC2) is required for several aspects of embryogenesis, including the maturation phase, and is sufficient to induce somatic embryo development in vegetative cells. Here, we demonstrate that LEC2 directly controls a transcriptional program involved in the maturation phase of seed development. Induction of LEC2 activity in seedlings causes rapid accumulation of RNAs normally present primarily during the maturation phase. Several RNAs encode proteins with known roles in maturation processes, including seed-storage and lipid-body proteins. Clustering analyses identified other LEC2-induced RNAs not previously shown to be involved in the maturation phase. We show further that genes encoding these maturation RNAs all possess in their 5' flanking regions RY motifs, DNA elements bound by other closely related B3 domain transcription factors. Our finding that recombinant LEC2 specifically binds RY motifs from the 5' flanking regions of LEC2-induced genes provides strong evidence that these genes represent transcriptional targets of LEC2. Although these LEC2-induced RNAs accumulate primarily during the maturation phase, we show that a subset, including AGL15 and IAA30, accumulate in seeds containing zygotes. We discuss how identification of LEC2 target genes provides a potential link between the roles of LEC2 in the maturation phase and in the induction of somatic embryogenesis.

Arabidopsis↗
PubMed1994

A Seed Shape Mutant of Arabidopsis That Is Affected in Integument Development.

A seed shape mutant of Arabidopsis was isolated from an ethyl methanesulfonate-treated population. Genetic analysis revealed that the heart-shaped phenotype was maternally inherited, showing that this is a testa mutant. This indicated the importance of the testa for the determination of the seed shape. This recessive aberrant testa shape (ats) gene was located at position 59.0 on chromosome 5. A comparison was made between ovules and developing and mature seeds of the wild type and of the mutant using light and scanning electron microscopy. We showed that the mutant seed shape is determined during the first few days after fertilization, when the embryo occupies only a very small part of the seed. The integuments of ats ovules consisted of only three rather than five cell layers. In double mutants, the effect of ats was additive to other testa mutations, such as transparent testa, glabra (ttg), glabrous2 (gl2), and apetala2 (ap2). The ats mutation resulted in a reduced dormancy, which was maternally inherited. This effect of a testa mutation on germination was also seen in ttg seeds, in which the outer layer of the testa was disturbed. This indicated the importance of the testa as a factor in determining dormancy in Arabidopsis.

Journal Article↗
PubMed2002

Regulation of pectic polysaccharide domains in relation to cell development and cell properties in the pea testa.

The occurrence of pectic polysaccharide epitopes in cells and tissues of the pea testa during late stages of seed development have been examined in relation to anatomy and cell properties. Homogalacturonan, in a highly methyl-esterified form, was present throughout late development in all pea testa cell walls, including the thickened cell walls of the outer macrosclereid layer. Two epitopes, characteristic of the side-chains of the rhamnogalacturonan-I domain of pectic polysaccharides, occurred in restricted and separate cell layers of the pea testa. A (1-->4)-beta-D-galactan epitope was restricted to regions of the outer cell wall of the testa and to inner regions of the macrosclereid layer at 20 DAA and was absent from the osteosclereid and parenchyma cell walls. By 25 DAA the (1-->4)-beta-D-galactan epitope occurred only in the outer epidermal cell walls. A (1-->5)-alpha-L-arabinan epitope was also dependent on the developmental stage of the seed and was found with greatest abundance in the walls of the inner parenchyma cells. Cell separation studies indicated that, although calcium cross-links were involved in the maintenance of the link between the macrosclereid layer and proximal cell layers, most cell-to-cell adhesion in the testa was not due to calcium- or ester-based bonds.

Antibodies, Monoclonal↗
PubMed2002

A gene encoding a protein modified by the phytohormone indoleacetic acid.

We show that the expression of an indole-3-acetic acid (IAA)-modified protein from bean seed, IAP1, is correlated to the developmental period of rapid growth during seed development. Moreover, this protein undergoes rapid degradation during germination. The gene for IAP1, the most abundant protein covalently modified by IAA (iap1, GenBank accession no. ) was isolated and cloned from bush bean (Phaseolus vulgaris) seeds. The 957-bp sequence encodes a 35-kDa polypeptide. IAA-modified proteins represent a distinct class of conjugated phytohormones and appear in bean to be the major form of auxin in seeds. IAA proteins also are found at other stages of development in bean plants. Our immunological and analytical data suggest that auxin modification of a small class of proteins may be a feature common to many plants.

Amino Acid Sequence↗
PubMed2005

Evidence of a role for tyrosine dephosphorylation in the control of postgermination arrest of development by abscisic acid in Arabidopsis thaliana L.

In the present paper evidence is presented indicating that tyrosine dephosphorylation is a key regulatory mechanism in postgermination arrest of Arabidopsis thaliana L. seed development mediated by abscisic acid (ABA). By using phenylarsine oxide (PAO), an inhibitor of tyrosine phosphatases, the sensitivity to the inhibitory effect of ABA on seed germination is enhanced. Consistent with this finding, we demonstrate that the ABA-responsive gene, RAB18, is hyperinduced in seeds imbibed in ABA plus PAO, compared with seeds imbibed only with ABA.

Abscisic Acid↗
PubMed1994

Triticum aestivum puroindolines, two basic cystine-rich seed proteins: cDNA sequence analysis and developmental gene expression.

From a mid-maturation seed cDNA library we have isolated cDNA clones encoding two Triticum aestivum puroindolines. Puroindoline-a and puroindoline-b, which are 55% similar, are basic, cystine-rich and tryptophan-rich proteins. Puroindolines are synthesized as preproproteins which include N- and C-terminal propeptides which could be involved in their vacuolar localization. The mature proteins have a molecular mass of 13 kDa and a calculated isoelectric point greater than 10. A notable feature of the primary structure of puroindolines is the presence of a tryptophan-rich domain which also contains basic residues. A similar tryptophan-rich domain was found within an oat seed protein and a mammalian antimicrobial peptide. The ten cysteine residues of puroindolines are organized in a cysteine skeleton which shows similarity to the cysteine skeleton of other wheat seed cystine-rich proteins. Northern blot analysis showed that puroindoline genes are specifically expressed in T. aestivum developing seeds. No puroindoline transcripts as well as no related genes were detected in Triticum durum. The identity of puroindolines to wheat starch-granule associated proteins is discussed as well as the potential role of puroindolines in the plant defence mechanism.

Amino Acid Sequence↗