Fusicoccin-Induced Changes in the Translatable RNAs of Etiolated Pea Stem Tissue

The fungal toxin fusicoccin (FC) was found to induce substantialincreases in the abundance of specific translatable RNAs overseveral hours, concomitantly with tissue expansion, in segmentsof etiolated pea internodes. The FC-induced RNAs encoded somerelatively basic polypeptides of MWs 27.5–29.2 kDa, andsome relatively acidic polypeptides of MWs 12.5–15.5 kDa.The earliest detectable increases in the FC-induced translationproducts occurred after 1.5–2.5 h. Auxin treatment causeda different overall pattern of changes in translation productspots, though some induced spots appeared to be common to bothtreatments. The possible significance of these observationsis discussed in relation to other factors known to alter geneexpression in plant tissues. Key words: Pea, fusicoccin, auxin, genes     

Differences in Photoresponse and Phytochrome Spectrophotometry Between Etiolated and De-etiolated Pea Stem Tissue

Morphologically similar pea plants having a 4-fold difference in spectrophoto-metrically detectable phytochrome can be produced by pretreatment of etiolated plants with red light (R) or with red and far-red light combined (RF). A search for response differences which could be ascribed to differences in phytochrome content has resulted only in the establishment of differences due to de-etiolation. Segments of etiolated plants differ from those of plants de-etiolated by R and RF pretreatments in 2 ways. Segments from etiolated plants appear to respond rapidly to the far-red absorbing form of phytochrome (P_FR), while segments from de-etiolated plants do not respond rapidly to P_FR. This statement is based upon 2 observations: (i) the red light induced growth inhibition in segments from etiolated plants rapidly escapes reversibility by far-red light, while with segments from R or RF pretreated plants, the red light effect is fully reversed by subsequent far-red light for up to 2 hr; and (ii) segments from etiolated plants were inhibited to a greater degree than were segments from RF pretreated plants when various photostationary state levels of P_FR were maintained for 30 or 90 min and then removed by photoconversion to P_R. The in vivo nonphotochemical transformation curves of the phytochrome of etiolated and RF pretreated plants appear to differ in 2 related respects: (i) the amount of phytochrome destroyed in de-etiolated tissue is greater than that in etiolated tissue, perhaps as a result of the fact that (ii) the rate and extent of apparent reversion of P_FR to P_R in etiolated tissue is about twice that in de-etiolated tissue.     

Influence of Ethylene on Indole-3-acetic Acid Concentration in Etiolated Pea Epicotyl Tissue

Indole-3-acetic acid levels are diminished about 50% in 5- to 6-day-old epicotyls of etiolated pea (Pisum sativum L.) seedlings treated with 10 to 36μl/l ethylene for 18 to 24 hr.     

Binding Proteins to Phytochrome A in Etiolated Pea Seedlings

In order to detect and characterize a putative receptor(s) fora signal from PhyA, proteins that bind to purified pea PhyAwere searched for in the crude extract of etiolated pea seedlingswith affinity chromatography. PhyA was coupled to the columnsubstrate either in P_R form (P_R column) or in red-irradiatedform (P_FR column). The coupled PhyA of both columns retainsits spectral reversibility between P_R and P_FR, although theirpeptide mapping by trypsin digestion suggests that the C-terminalhalf of PhyA in the P_FR column is partially fixed in P_FR structure.15 polypeptides were detected reproducibly in the elution fromthe P_FR column by silver-staining of SDS-PAGE. These 15 polypeptidesmay form two complexes judging from their elution profiles.Of the 15 polypeptides, the 6 major polypeptides have approximatemol wt of 80, 55, 53, 46, 40 and 35 kDa. On the other hand,only a trace amount of protein, which mainly consists of the46 kDa species, was eluted from P_R column, indicating the presenceof P_FR-specific BPs in the crude extract of etiolated pea seedlings.Of the 6 major polypeptides, the 40 kDa species binds to thePhyA in a photoreversible manner. (Received June 19, 1998; Accepted December 19, 1998)     

Changes in Lipid Composition during Greening of Etiolated Pea Seedlings

After 7 days of germination in the dark, the three sections of pea seedlings studied (cotyledons, stems, and young leaves) are rich in linoleic acid; after illumination of the seedlings a very significant increase in linolenic acid is observed in the young leaves section, whereas only small variations are noted in the fatty acid composition of the other sections. The increase in linolenic acid results from the increase in galactolipid content of the young leaves; these already linolenic acid-rich galactolipids are present but only in small amounts in the etiolated seedlings (10% of total lipid).     

Nuclear Magnetic Resonance Studies of Sodium and Potassium in Etiolated Pea Stem

Based on nuclear magnetic resonance (NMR) spectroscopy and other evidence, it has been argued that tissues accumulate, and retain, ions in a binding process by a highly structured water-protoplasm system; thus active membrane transport need not be involved. Recent evidence has accounted for the loss of resonance intensity usually found when investigating quadrupolar ions in animal tissue. Using continuous wave NMR spectroscopy, we have examined two quadrupolar ions, Na⁺ and K⁺, in pea stem cells where about 90% of the ion content is in the largely aqueous vacuoles having a membrane barrier. The NMR resonances from these ions correspond to almost 100% of that expected from independent measurements of total ion content. This indicates that the ions are retained as free ions after accumulation. The small fraction which is NMR invisible may represent ions in an ordered, anisotropic environment, such as that in the wall or cytoplasm.     

Phytochrome Control of Cell Wall-bound Hydroxyproline Content in Etiolated Pea Epicotyls

The red light inhibition of growth of the intact pea (Pisum sativum L. cv. Alaska) third internode was correlated with an increase in the content of cell wall-bound hydroxyproline. These changes were detected 3 hours after irradiation, and possibly at 1 hour. Far red light reversed the effects of red light. The iron chelator α,α′-dipyridyl reversed the red light effects on both growth and hydroxyproline content. Using segments incubated in vitro, no phytochrome-mediated change in hydroxyproline content could be observed, perhaps because of an overwhelming wounding response. If plants were irradiated in situ and grown for 8 hours before excision and incubation of segments, some enhancement of hydroxylation by red light was detectable both colorimetrically and radioisotopically. The red light inhibition of segment growth was reversed by α,α′-dipyridyl. These results are examined in reference to the role of extensin in normal and induced growth cessation.     

Identification of a Triterpenoid Saponin in Etiolated Pea Shoots as Phytochrome Killer

Phytochrome killer, a substance which instantaneously causesin vitro spectral denaturation of phytochrome, was isolatedin the pure state from the methanol extract of etiolated peashoots by Sephadex G-25, charcoal and silica gel chromatographies.Chemical and spectrometric (nuclear magnetic resonance, massand infra-red) analyses disclosed that this substance was identicalwith soyasaponin I, a triterpenoid saponin. Most of the phytochromekiller activity in the methanol extract was ascribable to soyasaponinI. The content of this saponin was 61 µg/g fr wt in theetiolated epicotyl tissue and 27 µg/g fr wt in the greenepicotyl tissue. (Received August 15, 1981; Accepted December 16, 1981)     

Changes in Polyamine Titer in Etiolated Pea Seedlings Following Red Light Treatment

The polyamines agmatine, cadaverine, putrescine, spermidineand spermine were measured by means of thin layer chromatographyand high performance liquid chromatography in buds and in 5mm long subapical sections of the 3rd internode of 6-day-oldetiolated pea seedlings. The polyamine pattern of each organwas specific, relative quantities varying with age and growth.While agmatine, putrescine, spermidine and spermine were presentin buds and in tissues of the 3rd internode, cadaverine wasfound in the 3rd internode only. Concentrations of spermidineand spermine were higher in the bud than in the 3rd internode,and the highest putrescine titer was found in the internode.Short exposure of etiolated seedlings to red light (5 min) increasedbud development while inhibiting growth of the 3rd internode.In general, exposure to red light increased the titer of putrescine,agmatine and spermidine in the bud, whereas in the internodea reverse pattern was found, i.e., internodes of seedlings growingin the dark yielded higher titer of polyamines in general, andagmatine in particular. These results are particularly pronounced18 hr after exposure to red light. A link between phytochrome-controlledgrowth and polyamine titer is suggested. ² On sabbatical leave from the Hebrew University of Jerusalem,Department of Horticulture, Rehovot, Israel. ³ Supported by a grant from the Turkish Government; Permanentaddress: Department of General Botany, University of Istanbul,Suleymaniye, Istanbul, Turkey. ¹ Supported by a grant from NSF to A.W.G. (Received August 24, 1981; Accepted October 22, 1981)     

豌豆黄化苗114kD光敏色素的纯化

以25℃暗室中培养7d的阿拉斯加豌豆黄化苗为材料,采用改进的Yamamoto等方法,制备光敏色素粗提取液,再经DEAE-Sephacel,Brushite以及DEAE-Agarose柱层析得到初步提纯的光敏色素。然后再通过豌豆光敏色素抗体mAP1-Sepharose 4B亲和层析得到了提纯的豌豆114 kD光敏色素,经SDS-PAG电泳检测为一条带,并具有类似于纯净光敏色素的吸收光谱。     

Transport and Metabolism of Sucrose versus Hexoses in Relation to Growth in Etiolated Pea Stem

Sucrose, supplied to detached pea (Pisum sativum L. var Alaska) epicotyls through cut bases, supported better growth of apical tissue than supplied glucose and/or fructose. The hexoses were converted mainly to sucrose in basal regions of the epicotyl but some moved as such through the epicotyl and accumulated at the apex (plumule) at a rate faster than sucrose. A greater proportion of the carbon derived from supplied hexoses than from sucrose was used for synthesis of ethanol-insoluble products throughout the epicotyl. By use of asymmetrically labeled sucrose, it was shown that neither hexose moiety was used preferentially for the synthesis of metabolites. Supplied sucrose moved as such only up to the region of cell elongation where it was hydrolyzed and completely equilibrated before moving into more apical regions. The results indicate that better growth with supplied sucrose than hexose could not have resulted from differential effects on cell division, more rapid uptake or transport of sucrose, enhanced wall synthesis, or cleavage by sucrose synthase. It is concluded that transported sucrose versus hexoses must undergo or evoke different reactions which affect growth in the region of cell elongation.     

Properties and Possible Physiological Significance of Cell Wall Calcium Binding in Etiolated Pea Epicotyls

Baydoun, E. A-H. and Brett, C. T. 1988. Properties and possiblephysiological significance of cell wall calcium binding in etiolatedpea epicotyls.—J. exp. Bot. 39: 199–208. The binding of ⁴⁵Ca²⁺ ions to cell walls prepared from pea epicotylswas examined in young and old parts of the epicotyl, and wasfound to be considerably greater, on a carbohydrate basis, inthe older, non-growing cells. A similar comparison between light-and dark-grown stems showed greater binding in the dark-grownstems. The polygalacturonase-insensitive component of the bindingcontained at least three types of binding with different affinities,and had an apparent pK of 4.3. The specificity of the bindingfor calcium ions was examined and a considerable degree of specificitywas observed. The specificity of inhibition by calcium of epicotylelongation was similar to the specificity of calcium binding.A specific calcium chelator, EGTA, when present at a concentrationof above 10 mol m^–3, promoted the extension of matureregions of the epicotyl, while inhibiting extension of youngertissue. Key words: Cell wall, calcium, pea epicotyl     

Effects of Some Growth Regulators on Polyamine Biosynthetic Enzymes in Etiolated Pea Seedlings

This study was designed to examine possible links between polyaminebiosynthesis and effects of growth regulatory compounds. Anauxin (IAA), a cytokinin [benzyladenine; benzylaminopurine (BAP)],an ethylene source (ethephon) and abscisic acid (ABA) were individuallyapplied to terminal buds of excised etiolated or red light (R)-exposedpea epicotyls. Effects were noted on bud fresh weight and onthe two main enzymes of putrescine biosynthesis, arginine decarboxylase(ADC; EC 4.1.1.19 [EC] ) and ornithine decarboxylase (ODC; EC 4.1.1.17 [EC] ).As previously reported [Dai and Galston (1981) Plant Physiol.67: 266], both bud growth and ADC activity are increased byR light. In such buds, ADC is raised further by 1–10 µMBAP or ABA and inhibited by 1–10 µM IAA or ethylene(50 mg/liter or more of ethephon). In all cases, effects ofR-irradiation plus 1 mM growth regulators on ODC activity wasthe inverse of their effects on ADC, indicating independentcontrol of these pathways. These results do not support theview that putrescine biosynthetic activity is correlated withgrowth in etiolated pea seedlings. ¹Supported by a grant from NSF to A.W.G. ²Supported by a grant from the Turkish Government. Permanentaddress: Department of General Botany, University of Istanbul,S?leymaniye, Istanbul, Turkey. ³On sabbatical leave from the Department of Horticulture, HebrewUniversity of Jerusalem, Rehovot, Israel. (Received September 22, 1983; Accepted February 28, 1984)     

Phytochrome-dependent Reduction of Nicotinamide Nucleotides in the Mitochondrial Fraction Isolated from Etiolated Pea Epicotyls

When mitochondria isolated from etiolated pea (Pisum sativum cv. Alaska) epicotyls were exposed briefly to red light, their ability to reduce exogenous NADP was enhanced. The red light effect was reversed by far red light. Photoreversible absorbance changes between 730 nm and 800 nm were spectrophotometrically detected in the purified mitochondria and its membrane fraction. The dehydrogenase activity in the mitochondria was heat-labile and was dependent on the presence of magnesium ion and appropriate substrates such as glucose 6-phosphate, isocitrate, pyruvate, 6-phosphogluconate, and succinate. The photoreversible effect was seen only for a few minutes after the irradiation, and was cancelled by hypotonic treatment or addition of Triton X-100. A similar but lesser effect was observed in the pea microsome fraction, whereas no photoreversible response was seen with a supernatant fraction resulting from centrifugation at 10⁵g for 30 minutes.