摘要:

Our increasing capabilities for quantitative hormone analysis and automated high resolution growth studies have allowed a reassessment of the classical Cholodny-Went hypothesis of gravitropism. According to this hypothesis, gravity induces redistribution of auxin toward the lower side of the organ and this causes the growth asymmetry that leads to reorientation. Arguments against the Cholodny-Went hypothesis that were based primarily on concerns over the timing and magnitude of the development of hormone asymmetry are countered by recent evidence that such asymmetry develops early and is sufficiently large to account for curvature. Thus, it appears that the Cholodny-Went hypothesis is fundamentally valid. However, recent comparative studies of the kinetics of curvature and the timing of the development of hormone asymmetry indicate that this hypothesis alone cannot account for the intricacies of the gravitropic response. It appears that time-dependent gravity-induced changes in hormone sensitivity as well as changes in sensitivity of the gravity receptor play important roles in the response.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

Plasma membranes obtained by two-phase partitioning of microsomal fractions from spinach (Spinacea oleraceaL. cv Medania) and sugar beet leaves (Beta vulgarisL.) contained relatively high NADH-ferricyanide reductase and NADH-nitrate reductase (NR; EC1.6.6.1) activities. Both of these activities were latent. To investigate whether these activities were due to the same enzyme, plasma membrane polypeptides were separated with SDS-PAGE and analyzed with immunoblotting methods. Antibodies raised against microsomal NADH-ferricyanide reductase (tentatively identified as NADH-cytochromeb5reductase, EC1.6.2.2), purified from potato (Solanum tuberosumL. cv Bintje) tuber microsomes, displayed one single band at 43 kilodaltons when reacted with spinach plasma membranes, whereas lgG produced against NR from spinach leaves gave a major band at 110 kilodaltons together with a few fainter bands of lower molecular mass. Immunoblotting analysis using inside-out and right-side-out plasma membrane vesicles strongly indicated that NR was not an integral protein but probably trapped inside the plasma membrane vesicles during homogenization. Proteins from spinach plasma membranes were solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl) dimethylammonio] 1-propane-sulfonate and separated on a Mono Q anion exchange column at pH 5.6 with fast protein liquid chromatography. One major peak of NADH-ferricyanide reductase activity was found after separation. The peak fraction was enriched about 70-fold in this activity compared to the plasma membrane. When the peak fractions were analyzed with SDS-PAGE the NADH-ferricyanide reductase activity strongly correlated with a 43 kilodalton polypeptide which reacted with the antibodies against potato microsomal NADH-ferricyanide reductase. Thus, our data indicate that most, if not all, of the truly membrane-bound NADH-ferricyanide reductase activity of leaf plasma membranes is due to an enzyme very similar to potato tuber microsomal NADH-ferricyanide reductase (NADH-cytochromeb5reductase).

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

Two anionic isoperoxidases were isolated from media ofAspergillus flavus-inoculated cotton (Gossypium hirsutumL.) ovule cultures and purified about 150-fold to apparent homogeneity by treatment with Cell Debris Remover and ion exchange chromatography on Accell QMA medium. These isoperoxidases were present in noninoculated cotton ovule cultures at low levels. The major activity peak (B) represented 90% of the recovered peroxidase activity and was electrophoretically homogeneous. The minor activity peak (A) was about 95% pure. Isoelectric focusing analysis showed that B was greater than 95% pure with respect to other peroxidase isozymes, while the enzyme in A was about 90% isozymically pure. Each isoperoxidase displayed a molecular mass of 56 kilodaltons by interpolation from denaturing gel electrophoresis. The B isozyme displayed a molecular mass of 55 kilodaltons by gel filtration chromatography. The pH optima for the cotton ovule isoperoxidases were similar, 5.0 for isozyme A and 6.0 for isozyme B. The isoelectric points for isozymes A and B were 4.2 and 4.4, respectively. Eugenol, guaiacol, and 3,3′,5,5′-tetramethylbenzidine were good electron donor substrates, whereas 4-aminoantipyrine was a poor substrate. The absorption spectrum of the material in B revealed a major peak at 400 nanometers and a minor peak at 280 nanometers. The molar extinction coefficient at 400 nanometers (pH 7.0) was calculated to be 1.07×105per square centimeter per mole. Amino acid analysis of isozyme B confirmed the acidic nature of this protein and identified a number of similarities to the anionic peroxidases from tobacco and potato. This glycoprotein was found to contain 12 to 14% sugar (by weight), mainly in the form of galactose and man

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

Two of four isozymes of superoxide dismutase (SOD) (EC1.15.1.1) were purified from Scots pine (Pinus sylvestrisL.) needles. One form was cytosolic (SOD-1) and the other was associated with chloroplasts (SOD-3). The holoenzyme molecular masses was estimated at approximately 35 kilodaltons by gel filtration. The subunit molecular weight of the dimeric enzymes was estimated to 16.5 kilodaltons (SOD-1) and 20.4 kilodaltons (SOD-3) on sodium dodecyl sulfatepolyacrylamide gels. The NH2-terminal sequence of the pine enzymes showed similarities to other purified superoxide dismutases located in the corresponding compartment. The cytosolic form revealed two additional amino acids at position 1 and 2 at the NH2-terminal. Both forms were cyanide- and hydrogenperoxide-sensitive and SOD-3 was found to contain approximately one copper atom per subunit, indicating that they belong to the cupro-zinc SODs. The isoelectric point was 4.9 and 4.5 for SOD-1 and SOD-3, respectively.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

The speed of ethylene-induced leaf abscission in cotton (Gossypium hirsutumL. cv LG-102) seedlings is dependent on leaf position (i.e.physiological age). Fumigation of intact seedlings for 18 hours with 10 microliters per liter of ethylene resulted in 40% abscission of the still-expanding third true (3°) leaves but had no effect on the fully expanded first true (1°) leaves. After 42 hours of fumigation with 50 microliters per liter of ethylene, total abscission of the 3°leaves occurred while<50% abscission of the 1°leaves was observed. On a leaf basis, endogenous levels of free IAA in 1°leaves were approximately twice those of 3°leaves. Free IAA levels were reduced equally (approximately 55%) in both leaf types after 18 hours of ethylene (10 microliters per liter) treatment. Ethylene treatment of intact seedlings inhibited the basipetal movement of [14C]IAA in petiole segments isolated from both leaf types in a dose-dependent manner. The auxin transport inhibitorN-1-naphthylphthalamic acid increased the rate and extent of ethylene-induced leaf abscission at both leaf positions but did not alter the relative pattern of abscission. Abscission-zone explants prepared from 3°leaves abscised faster than 1°leaf explants when exposed to ethylene. Ethyleneinduced abscission of 3°explants was not appreciably inhibited by exogenous IAA while 1°explants exhibited a pronounced and protracted inhibition. The synthetic auxins 2,4-D and 1-naphthaleneacetic acid completely inhibited ethylene-induced abscission of both 1°and 3°explants for 40 hours. It is proposed that the differential abscission response of cotton seedling leaves is primarily a result of the limited abscission-inhibiting effects of IAA in the abscission zone of the you

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

The regulation of electron transport in pea (Pisum sativumL.) leaf mitochondria under state 4 conditions has been investigated by simultaneously monitoring oxygen uptake, the steady-state reduction level of ubiquinone, and membrane potential. Membrane potentials were measured using a methyltriphenylphosphonium electrode while a voltametric technique was used to monitor changes in the steady-state reduction levels of quinone. It was found that the addition of glycine to mitochondria oxidising malate in state 4 led to a marked increase in the rate of O2uptake and increased both the membrane potential and reduction level of the quinone pool. Increases in the state 4 respiratory rate were attributed to both an increase in driving flux, due to increased Q-pool reduction, and in membrane potential. Due to the nonohmic behavior of the inner membrane, under these conditions, an increase in potential would result in a considerable rise in proton conductance. Measurement of dual substrate oxidation, in the presence ofn-propylgallate, revealed that the increase in respiratory activity was not mediated by the alternative oxidase. Similar increases in membrane potential and the level of Q-pool reduction were observed even in the presence of rotenone suggesting that the rotenone-insensitive pathway is a constitutive feature of plant mitochondria and may play a role in facilitating rapid state 4 rates even in the presence of a high energy charge.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

The fruit of the Alcobaca landrace of tomato (Lycopersicon esculentumMill.) have prolonged keeping qualities (determined by the allelea/c) and contain three times as much putrescine as the standard Rutgers variety (A/c) at the ripe stage (ARG Dibble, PJ Davies, MA Mutschler [1988] Plant Physiol 86: 338-340). Polyamine metabolism and biosynthesis were compared in fruit from Rutgers and Rutgers-a/c—a near isogenic line possessing the allelea/c, at four different stages of ripening. The levels of soluble polyamine conjugates as well as wall bound polyamines in the pericarp tissue and jelly were very low or nondetectable in both genotypes. The increase in putrescine content ina/cpericarp is not related to normal ripening as it occurred with time and whether or not the fruit ripened. Pericarp discs of both normal anda/cfruit showed a decrease in the metabolism of [1,4-14C]putrescine and [terminal labeled-3H]spermidine with ripening, but there were no significant differences between the two genotypes. The activity of ornithine decarboxylase was similar in the fruit pericarp of the two lines. Arginine decarboxylase activity decreased during ripening in Rutgers but decreased and rose again in Rutgers-a/cfruit, and as a result it was significantly higher ina/cfruit than in the normal fruit at the ripe stage. The elevated putrescine levels ina/cfruit appear, therefore, to be due to an increase in the activity of arginine decarboxylas

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

Specificities of three monoclonal antibodies (15-I-C5, DBPA 1, and MAC 62) raised against the plant hormone (S)-(+)-abscisic acid (ABA) have been compared. Immunological cross-reactivities against fifteen biologically active analogs of ABA were measured. The ABA analogs were altered at one or more of four positions: the double bonds in the ring, at C-2 C-3 and at C-4 C-5, and in the oxidation level at C-1. Several analogs were optically active with chiral centers at C-1′and C-2′. For cross-reactivity, all three monoclonal antibodies required the carboxylic acid group, and thecisconfiguration of the double bond at C-2 C-3 of the ABA molecule. Monoclonals 15-I-C5 and DBPA 1 required the entire ABA sidechain from the C-1 to C-1′, but these monoclonals did cross-react with analogs with the ring double bond reduced and the C-2′methylcisto the sidechain. Only MAC 62 recognized analogs containing an acetylene at C-4 C-5. MAC 62 had more strict requirements for the ring double bond, but gave some cross-reactivity with acetylenic analogs having a saturated ring. All three monoclonals had higher specificity for analogs having the same absolute configuration at C-1′as (S)-(+)-ABA. This work provides new information about the spatial regions of the ABA molecule that elicit immunological recognition, and serves as a basis for future investigations of the ABA receptor using ABA analogs and anti-idiotypic a

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

We screened a total of 1365 pea (Pisum sativum) lines for response to inoculation withAgrobacterium tumefaciens, strain B6, and characterized resistance in one cultivar, Sweet Snap. Sweet Snap seedlings were highly resistant to tumorigenesis under most conditions. Resistance was overcome at inoculum concentrations of greater than 109bacteria per milliliter. At such high concentrations, very small tumors developed on Sweet Snap in response to four wide-host-rangeAgrobacteriumstrains, but tumors on other cultivars were two-to sevenfold larger than those that formed on Sweet Snap. The hypervirulent strain A281 induced larger tumors on Sweet Snap than did otherAgrobacteriumstrains, but tumors on other genotypes were more than 100% larger than those on Sweet Snap. Physiological experiments suggested that tumorigenesis in Sweet Snap is not blocked in early stages of infection, and genetic analysis indicated that inheritance of resistance to crown gall is a quantitative trait. In addition to the observed resistance in Sweet Snap, three `supersusceptible' genotypes, which developed very large tumors, also were identified.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB

摘要:

Glucocerebrosides of whole rye (Secale ceraleL. cv Puma) leaf and plasma membrane were analyzed using gas chromatography-mass spectrometry and gas chromatography following hydrolysis or as intact molecules purified by reverse-phase high performance liquid chromatography. Fatty acids of acid-hydrolyzed leaf and plasma membrane glucocerebrosides consisted of>98 weight percent saturated and monounsaturated 2-hydroxy fatty acids which contained 16 to 26 carbon atoms. The major fatty acids detected were 2-hydroxynervonic acid (24:1h), 2-hydroxylignoceric acid (24:0h), 2-hydroxyerucic acid (22:1h), and 2-hydroxybehenic acid (22:0h). Long-chain bases of alkaline-hydrolyzed glucocerebrosides consisted primarily ofcis-transisomers of the trihydroxy base 4-hydroxysphingenine (t18:1) and the dihydroxy base sphingadienine (d18:2) with lesser amounts of 4-hydroxysphinganine (t18:0) and isomers of sphingenine (d18:1). Intact, underivatized glucocerebroside molecular species of rye leaf and plasma membrane were separated into more than 30 molecular species using reverse-phase HPLC. The molecular species composition of leaf and plasma membrane were quantitatively and qualitatively similar. The major molecular species was 24:1h-t18:1 which constituted nearly 40 weight percent of leaf and plasma membrane extracts. Several other species including 22:1h-t18:1, 24:1h-t18:1 (isomer), 22:0h-t18:1, 24:1h-d18:2, and 24:0h-t18:1 each comprised 4 to 8% of the total. It is anticipated that the high performance liquid chromatography procedure developed in this study to separate intact, underivatized lipid molecular species will be useful in future studies of the physical properties and biosynthesis of plant glucocerebrosides.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1991

数据来源: ASPB