Partial purification and characterization of the mRNA for alpha-amylase from barley aleurone layers

Alterations in gene expression in sorghum induced by the host-specific toxin from Periconia circinata

Susceptibility of sorghum to the fungal pathogen Periconia circinata and sensitivity to its host-specific toxin are determined by the semidominant allele at the pc locus. Pretreatment of susceptible seedlings with cycloheximide or cordycepin for 4 hr before treatment with the toxin protected the seedlings against toxin-induced loss of electrolytes and prevented development of disease symptoms. In vivo incorporation of [(3)H]leucine into protein was inhibited 91% and 47% by cycloheximide and cordycepin, respectively, but was not affected by the toxin. Gel electrophoresis and fluorography of in vivo-labeled proteins extracted from non-treated and toxin-treated root tips of near-isogenic susceptible and resistant lines revealed a selective increase in radioactivity of a protein band at M(r) 16,000 only in preparations from toxin-treated susceptible root tips. Two-dimensional gel electrophoresis separated the M(r) 16,000 band into four proteins and confirmed the increased rate of synthesis. Products of in vitro translation were substantially enriched with the four M(r) 16,000 proteins when total RNA from toxin-treated susceptible root tips was used in a cell-free protein-synthesizing system. Because the proteins that increase are common to both susceptible and resistant genotypes, the toxin apparently interferes with a regulatory function, perhaps a function of the pc locus, and thereby alters gene expression in the susceptible genotype. The data suggest but do not establish that phytotoxicity results from the increased rate of synthesis of the specific proteins.

Molecular cloning of tomato fruit polygalacturonase: Analysis of polygalacturonase mRNA levels during ripening

The expression of a gene encoding the cell wall-degrading enzyme polygalacturonase [poly(1,4-alpha-D-galacturonide) glucanohydrolase, EC 3.2.1.15] was characterized during tomato fruit ripening. Polygalacturonase was purified from ripe tomato fruit and used to produce highly specific antiserum. Immunoblot analyses detected a 45- and a 46-kDa protein in ripe fruit but immunoprecipitation of in vitro translation products of mRNA from ripe tomato fruit yielded a single 54-kDa polypeptide, suggesting post-translational processing. A plasmid cDNA library was prepared from poly(A)(+) RNA isolated from ripe tomato fruit. The cDNA library was inserted into a lambda-based expression vector, and polygalacturonase cDNA clones were identified by immunological screening. Hybrid-select translation experiments indicated that the cDNAs encode a 54-kDa in vitro translation product that is specifically immunoprecipitated with polygalacturonase antiserum. RNA-blot analysis indicated that the 1.9-kilobase polygalacturonase mRNA was virtually absent from immature-green fruit, accumulated steadily during the ripening process, and was at its highest level in red-ripe fruit. There was at least a 2000-fold increase in the level of polygalacturonase mRNA between immature-green and red-ripe tomato fruit. These studies show that the levels of polygalacturonase mRNA are developmentally regulated during tomato fruit ripening.

A novel approach to determine the glyphosate tolerant trait in soybeans

The ability of soybean breeders to accurately, economically, and rapidly determine the transfer of the CP4 gene, the gene which confers soybean tolerance to the herbicide glyphosate, to elite soybean lines is essential to development of new glyphosate tolerant soybean (GTS) cultivars. This research focused on a simple greenhouse screening procedure to replace large, costly, and laborious field screening. Non-GTS seed was determined to be susceptible to soaking in a 1% glyphosate solution for 4 h. This process is quicker, more efficient, and as reliable as field screening for determination of glyphosate susceptibility in soybean seed. Furthermore, this research clearly demonstrates that the metabolic pathway of glyphosate activity, the shikimate acid pathway, is active, and the target enzyme of glyphosate, 5-enol-pyruvyl-shikimate-3-phosphate synthase, is present during seed germination.

Response of selected horseweed (Conyza canadensis (L.) Cronq.) populations to glyphosate

Horseweed (Conyza canadensis (L.) Cronq.) seed was collected in Illinois, Indiana, Kentucky, Mississippi, Missouri, and Ohio to determine susceptibility of different horseweed biotypes to glyphosate. Horseweed resistant to glyphosate was found in Mississippi, Ohio, and western Tennessee. In a separate experiment examining Tennessee biotypes, a dose response curve demonstrated that four times as much glyphosate was needed to achieve a 50% fresh weight reduction (GR(50)) in resistant biotypes when compared to a susceptible biotype. Resistant biotypes from Tennessee displayed a GR(50) of 1.6 kg/ha as compared to a GR(50) of 0.4 kg/ha in a susceptible horseweed population. Although growth was reduced, the resistant plants did not completely die and could potentially produce seed. Variation in glyphosate resistance was found among the populations tested.

Inclusion of polyvinylpyrrolidone in the polymerase chain reaction reverses the inhibitory effects of polyphenolic contamination of RNA

Polysaccharides, secondary metabolites and poly-phenolics are known to co-isolate with nucleic acids from plant tissues resulting in inhibition of molecular manipulations. RNA isolated from the polyphenolic-rich resurrection plant, Myrothamnus flabellifolius, was demonstrated to inhibit a standard polymerase chain reaction used as an assay despite the inclusion of the polyphenolic-binding compound poly(1-vinylpyrrolidone-2) (PVP) into the RNA isolation medium. This inhibition was, however, reversed by the addition of PVP into the PCR mixture itself. Confirmation of the inhibitory effect of polyphenolics on PCR was obtained by addition of green tea polyphenolics to the standard PCR assay. This inhibition was also reversed by the simultaneous inclusion of PVP.

Structure of the tomato Adh2 gene and Adh2 pseudogenes, and a study of Adh2 gene expression in fruit

A cDNA library was constructed from RNA from the pericarp of ripe tomato fruit and four cDNAs encoding ADH2 were isolated and characterized. The cDNAs encode a peptide 379 amino acids in length. They hybridized strongly with a 1.8 kb RNA species well represented in RNA from ripe, but not from mature, unripe fruit, and strongly to a similar RNA species present in hypoxic, but not in aerobic roots. Northern analysis showed that the mRNA for ADH2 in fruit increased in abundance through ripening, particularly during late ripening. In pericarp tissue of fruit, the Adh2 mRNA level increased to a maximum within 8-16 h of exposure to atmospheres with 3% (v/v) oxygen, and returned to the basal level within 16 h of a return to air. The mRNA level was sensitive to the oxygen level in the atmosphere, increasing 20-fold in 12% (v/v) oxygen and 100-fold in 3% oxygen. The homologous tomato Adh2 gene was isolated from a genomic library. The gene has an overall length of 2334 bp from transcription start site to poly(A) addition site and includes eight introns. Southern blot analysis of tomato genomic DNA identified multiple Adh2-related sequences. Two of these, PSA1 and PSA2, were cloned and found to have 94% similarity with each other and 77% similarity with the tomato Adh2 gene over a 1000 bp region. The homologous regions include introns and exons but the equivalent exons contain frame shifts, deletions and stop codons. The two regions are therefore presumptive pseudogenes.

Mapping of beta-tubulin genomic sequences in hexaploid oat (Arena sativa L.)

The allohexaploid nature of Avena sativa L. (2n=6x=42) and the availability of aneuploid lines was exploited in designing a strategy for mapping beta-tubulin sequences in the oat genome. Evidence for a minimum of eight beta-tubulin genes was obtained by Southern-blot analysis. Three betatubulin sequences were localized to chromosomes using DNA from monosomic and nullisomic lines in the variety Sun II. One sequence was localized to the chromosome missing in nullisome I. Two other sequences were mapped to satellite chromosome 2, the chromosome that is missing in nullisome VIII and to which one ribosomal RNA gene cluster had previously been mapped. Restriction fragments carrying these two beta-tubulin genomic sequences and the cluster of ribosomal RNA sequences were missing in DNA from nullisomics VIII, IX and X, suggesting that all three nullisome classes are deficient for an identical chromosomal segment that includes these three loci. This study demonstrates how molecular analyses can be used to characterize aneuploid stocks and to better define their genetic constitution.

Control of transient expression of chimaeric genes by gibberellic acid and abscisic acid in protoplasts prepared from mature barley aleurone layers

Gibberellic acid (GA3) and abscisic acid (ABA) control the transcription of alpha-amylase genes in barley aleurone cells. This control is likely to be exerted through cis-acting hormone-responsive elements in the promoter region of the gene. In order to further define these elements, we have developed procedures for obtaining transient expression of chimaeric genes in protoplasts prepared from mature barley aleurone layers. Constructs with heterologous constitutive promoters and with heterologous and homologous GA3- and ABA-regulated promoters were expressed specifically by these cells. This system would appear to offer great potential in gene regulation studies especially for hormonally regulated homologous genes. Functional analysis of a barley alpha-amylase gene has been performed using this system. A 2050 bp fragment from a high-pI alpha-amylase gene was fused to a reporter gene (GUS) and control of its expression was examined. Deletion analysis of this promoter fragment showed that major GA- and ABA-responsive elements occurred between 174 and 41 bp upstream from the transcription initiation site.

The organization and expression of a maize ribosomal protein gene family

We have isolated several Zea mays cDNAs encoding the 40S subunit ribosomal protein S14. In maize, this ribosomal protein is encoded by a small multigene family, at least three members of which are expressed. S14 transcript levels are highest in mitotically active tissues, such as seedling shoot, developing endosperm, and tassel primordia, and lowest in tissues with little cell division, such as mature leaf and root. Very little S14 RNA is present in pollen, suggesting that translation of pollen mRNAs during pollen germination uses preformed ribosomes. During kernel development, the highest levels of S14 transcripts in endosperm tissue are found at 10-12 days postpollination; S14 RNA levels decline continuously from this point onward. The period of maximal expression of the S14 ribosomal protein gene appears to precede the onset of storage protein synthesis and does not correlate with the reported times of increased nucleolar volume or genome amplification.

Maize glutamine synthetase cDNAs: isolation by direct genetic selection in Escherichia coli

Maize glutamine synthetase cDNA clones were isolated by genetic selection for functional rescue of an Escherichia coli delta glnA mutant growing on medium lacking glutamine. The Black Mexican Sweet cDNA library used in this study was constructed in pUC13 such that cDNA sense strands were transcribed under the control of the lac promoter. E. coli delta glnA cells were transformed with cDNA library plasmid DNA, grown briefly in rich medium to allow phenotypic expression of the cDNAs and the pUC13 ampr gene, and challenged to grow on agar medium lacking glutamine. Large numbers of glutamine synthetase cDNA clones have been identified in individual 150-mm Petri dishes; all characterized cDNA clones carry complete coding sequences. Two cDNAs identical except for different 5' and 3' termini have been sequenced. The major open reading frame predicts a protein with an amino acid sequence that exhibits striking similarity to the amino acid sequences of the predicted products of previously sequenced eukaryotic glutamine synthetase cDNAs and genes. In addition, the maize glutamine synthetase cDNAs were shown to contain a 5' mini-ORF of 29 codons separated by 37 nucleotide pairs from the major ORF. This mini-ORF was shown not to be essential for the functional rescue of the E. coli delta glnA mutant. Expression of the cDNAs in E. coli is presumed to be due to the function of a polycistronic hybrid lac messenger RNA or translational fusions encoded by the pUC plasmids. Proteins of the expected sizes encoded by two different pUC clones were shown to react with antibodies to tobacco glutamine synthetase.

Induction of 33-kD and 60-kD Peroxidases during Ethylene-Induced Senescence of Cucumber Cotyledons

Ethylene enhanced the senescence of cucumber (Cucumis sativus L. cv ;Poinsett 76') cotyledons. The effect of 10 microliters per liter ethylene was inhibited by 1 millimolar silver thiosulfate, an inhibitor of ethylene action. An increase in proteins with molecular weights of 33 to 30 kilodaltons and lower molecular weights (25, 23, 20, 16, 12, and 10 kilodaltons) were observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels after ethylene enhanced senescence. The measurement of DNase and RNase activity in gels indicated that these new proteins were not nucleases. Two proteins from ethylene-treated cotyledons were purified on the basis of their association with a red chromaphore and subsequently were identified as peroxidases. The molecular weights and isoelectric points (pI) of two of these peroxidases were 33 kilodaltons (cationic, pI = 8.9) and 60 kilodaltons (anionic, pI = 4.0). The observation that [(35)S]Na(2)SO(4) was incorporated into these proteins during ethylene-enhanced senescence suggests that these peroxidases represent newly synthesized proteins. Antibodies to the 33-kilodalton peroxidase precipitated two in vitro translation products from RNA isolated from ethylene-treated but not from control cucumber seedlings. This indicates that the increase in 33-kilodalton peroxidase activity represents de novo protein synthesis. Both forms of peroxidase degraded chlorophyll in vitro, which is consistent with the hypothesis that peroxidases have catabolic or scavenging functions in senescent tissues.

Characterization of a class of small auxin-inducible soybean polyadenylated RNAs

Four new auxin-responsive RNAs from soybean (Glycine max (L.) Merr., var. Wayne) are described. The RNAs were identified by hybridization to three cDNA probes obtained from a library enriched for sequences which increase in abundance within 60 min after 2,4-D (2,4-dichlorophenoxyacetic acid) treatment. These RNAs appear to define a new class of small (i.e. approximately 550 nucleotides) RNAs that respond extremely rapidly to application of exogenous auxin. In excised elongating hypocotyl sections, an increase in the abundance of these RNAs can be detected 2 to 5 min after treatment with 50 μM 2,4-D. This response is half maximal after 10 min and reaches steady state in 60 min. RNA blot analysis shows that these RNAs are expressed differentially in various parts of the seedling. The degree of inducibility by auxin is also organ-specific, with the elongating hypocotyl being the most responsive of the organs tested. The RNAs display identical response specificities with one exception. Accumulation of one RNA, designated 10A, is completely abolished by simultaneous addition of cycloheximide and 2,4-D. This RNA also displays a different 2,4-D dose response than other RNAs examined. These results suggest that more than one mechanism is involved in rapid modulation of gene expression by auxin.

Changes in cotyledon mRNA during floral induction of Pharbitis nil CV. Violet

Floral induction in seedlings of Pharbitis nil Choisy cv. Violet, with one cotyledon removed, was manipulated by applying various photoperiodic treatments to the remaining cotyledon. Populations of polyadenylated RNA from treated cotyledons were examined to identify messages specifically involved in floral induction. The RNA was translated in vitro using a wheat-germ system, and the resulting translation products were analysed by two-dimensional polyacrylamide gel electrophoresis. Substantial qualitative and quantitative differences were found between mRNA from cotyledons of seedlings kept in continuous light (non-induced) and of seedlings given a 16-h dark period (induced). In contrast, inhibition of flowering with a night-break resulted only in one detectable, quantitative difference in mRNA.

Cloning and expression of a cDNA encoding a maize glutathione-S-transferase in E. coli

The isolation and characterization of a family of maize glutathione-S-transferases (GST's) has been described previously. These enzymes are designated GSTs I, II and III based on size, substrate specificity and responsiveness to safeners. GST III has been shown to act on the herbicide alachlor as well as the commonly used substrate 1-chloro-2,4-dinitrobenzene (CDNB). Clones were isolated from a maize cDNA library in lambda gt10. Three clones contained the entire coding region for GST III. The sequences of these clones were consistent with the known amino terminal GST III protein sequence. Moreover, expression of one of these clones in E. coli resulted in a GST activity as measured with both CDNB and alachlor, proving that at least one of the clones encodes an active GST III species. With the enzyme expressed in E. coli it will become possible to study enzyme structure-function relationships ex planta. While a number of different GST proteins are present in maize tissue the GST III gene is present in single or low copy in the genome.

Messenger RNA encoding a glutathione-S-transferase responsible for herbicide tolerance in maize is induced in response to safener treatment

Glutathione-S-transferases (GST's) in maize represent a family of enzymes which conjugate glutathione to several major classes of pre-emergent, selective herbicides. Chemicals termed safeners have been demonstrated to increase the tolerance of maize toward such herbicides when the maize seed has been previously treated with safeners. It has subsequently been shown that corresponding increases in glutathione-S-transferase species occur. To determine whether these compounds act at a transcriptional level we have used synthetic oligonucleotide probes to isolate cDNA clones encoding the major GST polypeptide subunit, designated GST A. The identity of the clones has been confirmed by hybrid-selected mRNA translation and immunoprecipitation using antibodies made against this GST species as well as by production of active GST in yeast cells transformed with an expression vector containing the cloned DNA. GST A has been found to be encoded in a mRNA of 1.1 kb. Sequencing of cDNA products obtained by primer extension of maize mRNA using our oligonucleotide probes is consistent with this mRNA corresponding to the isolated cDNA clone. Using the clone as a probe for Northern analysis we have found a three to four-fold increase in the steady state level of this mRNA in maize tissue grown from safener-treated seeds. The level of safener which gives this induction is comparable to that required to obtain herbicide tolerance in the field.

Structural analysis of a maize gene coding for glutathione-S-transferase involved in herbicide detoxification

We have used the cDNA clone encoding maize glutathione-S-transferase (GST I) to isolate a genomic DNA clone containing the complete GST I gene. Nucleotide sequence analysis of the cDNA and genomic clones has yielded a complete amino acid sequence for maize GST I and provided the exon-intron map of its gene. The mRNA homologous sequences in the maize GST I gene consist of a 107 bp 5' untranslated region, a 642 bp coding region and ≈340 bp of the 3' untranslated region. They are divided into three exons by two introns which interrupt the coding region. The 5' untranslated spacer contains an unusual sequence of pentamer AGAGG repeated seven times. The inbred maize line (Missouri 17) contains a single gene for GST I, whereas the hybrid line (3780A) contains two genes. Nucleotide sequence analysis of the primer extended cDNA products reveals that the 5' untranslated regions of the two genes in the hybrid 3780A are identical except for a 6 bp internal deletion (or insertion). The amino acid sequence of maize GST I shares no apparent sequence homology with the published sequences of animal GST's and represents the first published sequence of a plant GST. re]19850813 ac]19851126.

Messenger RNAs from the Scutellum and Aleurone of Germinating Barley Encode (1-->3,1-->4)-beta-d-Glucanase, alpha-Amylase and Carboxypeptidase

Polyclonal antibodies raised against barley (1-->3,1-->4)-beta-d-glucanase, alpha-amylase and carboxypeptidase were used to detect precursor polypeptides of these hydrolytic enzymes among the in vitro translation products of mRNA isolated from the scutellum and aleurone of germinating barley. In the scutellum, mRNA encoding carboxypeptidase appeared to be relatively more abundant than that encoding alpha-amylase or (1-->3,1-->4)-beta-d-glucanase, while in the aleurone alpha-amylase and (1-->3,1-->4)-beta-d-glucanase mRNAs predominated. The apparent molecular weights of the precursors for (1-->3,1-->4)-beta-d-glucanase, alpha-amylase, and carboxypeptidase were 33,000, 44,000, and 35,000, respectively. In each case these are slightly higher (1,500-5,000) than molecular weights of the mature enzymes. Molecular weights of precursors immunoprecipitated from aleurone and scutellum mRNA translation products were identical for each enzyme.

Isolation and characterisation of cDNA clones for tomato polygalacturonase and other ripening-related proteins

Gene expression during the ripening of tomato fruit was investigated by cDNA cloning and hybrid-select translation. A cDNA library was prepared from poly(A)-containing mRNA from ripe tomato fruit and sreened by differential hybridization. 146 ripening-related cDNA clones were found. Eleven groups and eight unique clones have been identified so far. The sizes of the cloned cDNA inserts were determined and type-members for seven groups were used in hybrid selection experiments. Six of the seven clones encode translation products corresponding to six ripening related polypeptides detected previously by in vitro translation of total cytoplasmic RNA (14). One cDNA group codes for a Mr 48 000 protein that was identified as polygalacturonase on the basis of immunoprecipitation with specific antiserum raised against tomato polygalacturonase. re]19840918 rv]19850613 ac]19850618.

Comparative effects of ethylene and cyanide on respiration, polysome prevalence, and gene expression in carrot roots

Treatment of carrot roots (Daucus carota L.) with 10 microliters per liter ethylene in O(2) evokes a three- to four-fold increase in polysome prevalence and associated poly(A)(+) RNA. The increase in polysome prevalence is attended by a similar change in CO(2) evolution. The increase in polysomal poly(A)(+) mRNA constitutes primarily a generic increase in constitutive mRNAs as assayed by in vitro translation. However, changes in the relative abundance of several in vitro translatable ethylene specific mRNAs do occur.Cyanide, at concentrations which inhibit cytochrome oxidase, initiates a respiratory rise very similar in kinetics and magnitude to that evoked by ethylene. Moreover, the combined treatment with cyanide and ethylene evokes a respiratory response resembling that caused by ethylene or cyanide alone. Nevertheless, cyanide, in the presence of ethylene, significantly inhibits the increase in polysome prevalence and new gene expression associated with ethylene treatment of carrot roots. Separation of in vitro translation products by one-dimensional and two-dimensional gel electrophoresis shows that several new in vitro translation products appear in cyanide-treated carrots different from those evoked by ethylene. Engagement of the less energy efficient alternative electron transport path by cyanide may be responsible for inhibition of the normal ethylene associated increase in polysome prevalence and new gene expression. The implications of these results on regulation of respiratory metabolism are discussed and compared with the results for similar experiments with avocado fruit (Tucker and Laties 1984 Plant Physiol 74: 307-315) in which cyanide does not inhibit an ethylene educed increase in polysome prevalence and change in gene expression.

Interrelationship of Gene Expression, Polysome Prevalence, and Respiration during Ripening of Ethylene and/or Cyanide-Treated Avocado Fruit

Upon initiation of ripening in avocado fruit (Persea americana Mill. cv Hass) with 10 microliters/liter ethylene, polysome prevalence and associated poly(A)(+) mRNA increase approximately 3-fold early in the respiratory climacteric and drop off to preclimacteric levels at the peak of the respiratory climacteric. The increase in poly(A)(+) mRNA on polysomes early in the respiratory climacteric constitutes a generic increase in constitutive mRNAs. New gene expression associated with ripening is minimal but evident after 10 hours of ethylene treatment and continues to increase relative to constitutive gene expression throughout the climacteric. The respiratory climacteric can be temporally separated into two phases. The first phase is associated with a general increase in protein synthesis, whereas the second phase reflects new gene expression and accumulation of corresponding proteins which may be responsible for softening and other ripening characteristics. A major new message on polysomes that arises concomitantly with the respiratory climacteric codes for an in vitro translation product of 53 kilodaltons which is immunoprecipitated by antiserum against avocado fruit cellulase.Cyanide at 500 microliters/liter fails to affect the change in polysome prevalance or new gene expression associated with the ethylene-evoked climacteric in avocado fruit. Treatment of fruit with 500 microliters/liter cyanide alone initiates a respiratory increase within 4 hours, ethylene biosynthesis within 18 hours, and new gene expression akin to that educed by ethylene within 20 hours of exposure to cyanide.

In vivo synthesis and processing of cereal lectins

The synthesis and processing of cereal lectins was followed in vivo. The initial translation products of lectin genes are higher molecular weight (28 K) precursors, which are post-translationally processed in a single step into authentic lectin polypeptides (23 K). The conversion of precursor into mature product is a rather slow process (the precursor has a half life of 36 min) and is apparently not a prerequisite for biological activity since the precursor exhibits sugar binding activity. Because of the striking resemblances between the processing of cereal lectins and vectorial processing of cytoplasmatically made chloroplast, mitochondrial and glyoxysomal proteins, vectorial processing of cereal lectins might be a means of transporting these proteins through a membrane into an extra-cytoplasmic compartment.

Enzymic mechanism of starch breakdown in germinating rice seeds : 12. Biosynthesis of alpha-amylase in relation to protein glycosylation

The biosynthetic mechanism of alpha-amylase synthesis in germinating rice (Oryza sativa L. cv. Kimmazé) seeds has been studied both in vitro and in vivo. Special attention has been focused on the glycosylation of the enzyme molecule. Tunicamycin was found to inhibit glycosylation of alpha-amylase by 98% without significant inhibition of enzyme secretion. The inhibitory effect exerted by the antibiotic on glycosylation did not significantly alter enzyme activity.In an in vitro system using poly-(A) RNA isolated from rice scutellum and the reticulocyte lysate translation system, a precursor form of alpha-amylase (precursor I) is formed. Inhibition of glycosylation by Tunicamycin allowed detection of a nonglycosylated precursor (II) of alpha-amylase. The molecular weight of the nonglycosylated precursor II produced in the presence of Tunicamycin was 2,900 daltons less than that of the mature form of alpha-amylase (44,000) produced in the absence of Tunicamycin, and 1,800 daltons less than the in vitro synthesized molecule.The inhibition of glycosylation by Tunicamycin as well as in vitro translation helped clarify the heterogeneity of alpha-amylase isozymes. Isoelectrofocusing (pH 4-6) of the products, zymograms, and fluorography were employed on the separated isozyme components. The mature and Tunicamycin-treated nonglycosylated forms of alpha-amylase were found to consist of three isozymes. The in vitro translated precursor forms of alpha-amylase consisted of four multiple components. These results indicate that heterogeneity of alpha-amylase isozymes is not due to glycosylation of the enzyme protein but likely to differences in the primary structure of the protein moiety, which altogether support that rice alpha-amylase isozymes are encoded by multiple genes.

Gene expression during fruit ripening in avocado

The poly(A) (+)RNA populations from avocado fruit (Persea americana Mill cv. Hass) at four stages of ripening were isolated by two cycles of oligo-dT-cellulose chromatography and examined by invitro translation, using the rabbit reticulocyte lysate system, followed by two-dimensional gel electrophoresis (isoelectric focusing followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis) of the resulting translation products. Three mRNAs increased dramatically with the climacteric rise in respiration and ethylene production. The molecular weights of the corresponding translation products from the ripening-related mRNAs are 80,000, 36,000, and 16,500. These results indicate that ripening may be linked to the expression of specific genes.

In Vitro Synthesis and Processing of Wheat alpha-Amylase : TRANSLATION OF GIBBERELLIC ACID-INDUCED WHEAT ALEURONE LAYER RNA BY WHEAT GERM AND XENOPUS LAEVIS OOCYTE SYSTEMS

Wheat (Triticum aestivum) RNA was used to program synthesis of the alpha-amylase protein by Xenopus laevis oocytes. A 41,500-dalton protein was made which was identified as alpha-amylase by immunoprecipitation with rabbit anti-alpha-amylase antiserum raised against the purified wheat protein and by its co-migration with authentic alpha-amylase on sodium dodecyl sulfate polyacrylamide gels. Synthesis of alpha-amylase was dependent upon injection of RNA extracted from gibberellic acid-induced aleurone layers from wheat. The amount of alpha-amylase produced was proportional to the amount of RNA injected and reached a plateau within 4 hours after injection. When the same RNA was translated in a wheat germ cell-free translation system, a 43,000-dalton protein was produced. Addition of dog pancreas microsomal membranes to the wheat germ translation system resulted in processing of the alpha-amylase protein to a form which co-migrated with authentic alpha-amylase purified from malted wheat and with the protein synthesized in oocytes.

Enzymic Mechanism of Starch Breakdown in Germinating Rice Seeds: 10. IN VIVO AND IN VITRO SYNTHESIS OF alpha-AMYLASE IN RICE SEED SCUTELLUM

Scutellar tissues were dissected from germinating rice seeds and the incorporation of [(35)S]methionine into the alpha-amylase molecule was examined by in vivo and in vitro assay systems. Immunoprecipitation with monospecific anti-alpha-amylase immunoglobulin G raised against the purified enzyme preparation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography were used to identify alpha-amylase and its possible precursor molecule. Using freshly prepared scutellar tissues, it was demonstrated that alpha-amylase is synthesized de novo in the scutellar epithelium and secreted into endosperm. The synthesis of alpha-amylase directed by the polyadenylic acid-containing ribonucleic acid isolated from the scutellar tissues was also established using the translation system of either wheat germ extract or reticulocyte lysate. The immunoprecipitable product obtained in the in vitro translation system was smaller in molecular weight than that synthesized in vivo on the basis of mobilities in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results are discussed in relation to the processing of the nascent polypeptide precursor of the enzyme molecule and the introduction of the oligosaccharide chain to the cleaved polypeptide to make up the mature form of alpha-amylase.

Isolation and Characterization of Messenger RNAs for Seed Lectin and Kunitz Trypsin Inhibitor in Soybeans

The mRNAs for seed lectin and Kunitz trypsin inhibitor of soybean have been highly enriched by immunoadsorption of the polysomes synthesizing these proteins. Polysomes isolated from developing seed of variety Williams were incubated with monospecific rabbit antibodies produced against lectin subunits or trypsin inhibitor protein. The polysomal mixture was passed over a column containing goat anti-rabbit antibodies bound to Sepharose. Bound polysomes were eluted and the mRNA was selected by passage over oligo(dT)-cellulose. Lectin complementary DNA hybridized to an 1150-nucleotide message and trypsin inhibitor complementary DNA hybridized to a 770-nucleotide message in blotting experiments using total poly(A) RNA. Translation of soybean lectin mRNA using a rabbit reticulocyte lysate yielded a major polypeptide of 32,300 whereas the molecular weight for purified lectin subunits was 30,000. Trypsin inhibitor mRNA directed the synthesis of a 23,800-dalton polypeptide as compared to 21,500 daltons for trypsin inhibitor marker protein. Lectin specific polysomes could not be obtained from a soybean variety which lacks detectable lectin protein whereas trypsin inhibitor-specific polysomes were bound by immunoselection. These results confirmed the specificity of the immunoadsorption procedure and strongly indicated that the lectinless variety was deficient or substantially reduced in functional lectin mRNA.

Purification and Characterization of a Salt-extractable Hydroxyproline-rich Glycoprotein from Aerated Carrot Discs

The salt-extractable hydroxyproline-rich glycoprotein (HRGP) of the cell wall of aerated carrot root discs has been studied by polyacrylamide gel electrophoresis. The predominant proline-labeled protein extractable from the cell wall is rich in hydroxyproline as shown by its specific loss of (3)H from proline labeled in position 4 and its shift in electrophoretic mobility after labeling in the presence of an inhibitor of hydroxyproline synthesis. Unlabeled HRGP can be identified by staining gels for carbohydrate. The HRGP has been purified by ion exchange chromatography and CsCl gradient centrifugation. The HRGP consists of about 50% protein and 50% carbohydrate with an overall molecular weight of 86,000. The amino acid composition of the protein portion consists of 50% hydroxyproline, 19% basic amino acids, 12% serine, and 10% tyrosine. This glycoprotein accumulates in a salt-extractable pool in the cell wall beginning between 10 and 20 hours of aeration and may also become incorporated into the nonextractable portion of the cell wall.