Wound-induced Accumulation of Jasmonic Acid in Tissues of Potato Tubers

The level of jasmonic acid (JA) in medullary tissues of intactpotato tubers was found to be very low [ca. 4 ng (g fr wt)^–1].When the tissues were excised and incubated on moistened filterpaper, the level of JA began to increase rapidly, reached amaximum 4 h after excision and decreased thereafter. The maximumlevel of JA observed after 4 h was 450 ng (g fr wt)^–1.The level of JA-related compounds, as estimated by a bioassayfor potato tuber-inducing activity, showed similar fluctuationsto those in the level of JA, and neither methyl jasmonate nortuberonic acid could be detected in the tissues at any time.These results suggest that the increase in the level of JA isdue to the synthesis of JA and the decrease is due to the degradationof JA. The accumulation of JA was found only in tissues of dormanttubers that had been stored for less than 5 months and not inthose of sprouting tubers. Two inhibitors of animal phospholipaseA₂, namely, manoalide and quinacrine, did not inhibit the accumulationof JA, a result that suggests that activation of phospholipaseA₂ is not involved in the synthesis of JA. Actinomycin D andchloramphenicol also had no effect on the accumulation of JAbut cycloheximide had a considerable inhibitory effect. Theresults suggest that a newly synthesized protein(s) is the ratelimitingfactor in the biosynthesis of JA. (Received January 17, 1994; Accepted April 14, 1994)     

Invertase Activity and its Relation to Hexose Accumulation in Potato Tubers

Hexose accumulation was shown to occur in freshly harvestedmature potato tubers (Solanum tuberosum L.) both after storageat 10 ?C and when subsequently transferred to low temperature(3 ?C) storage. In general, changes in hexoses and sucrose werefound to be related to changes in acid invertase activity. Totalacid invertase activity (i.e. assayed after destroying the endogenousinvertase inhibitor present in the extracts) generally reflectedsugar changes more closely than did basal activity (i.e. assayedwith the inhibitor present). There was no evidence of a specificalkaline invertase. A comparison of the temperature responsesof cultivar Record with that of two SCRI² clones demonstrateddistinct genotypic variation in the extent of hexose accumulation.However, these differences were not always reflected by genotypicdifferences in total invertase activity. Key words: Invertase inhibitor, glucose, fructose, sucrose     

Induction of Proteinase Inhibitors in Tobacco Cell Suspension Culture by Elicitors of Phytophthora parasitica var. nicotianae

An elicitor preparation obtained from Phytophthora parasitica var. nicotianae, a pathogen of tobacco, induced an accumulation of proteinase inhibitors and a stimulation of ethylene synthesis in a tobacco (Nicotiana tabacum) cell suspension culture. About 30 micrograms per milliliter of elicitor were necessary for maximal induction of proteinase inhibitor accumulation, and the response was detectable after 12 hours of incubation with elicitor. Accumulation of proteinase inhibitors required de novo protein synthesis, since cycloheximide completely inhibited its elicitation, and actinomycin D inhibited it partially. One of the inhibitors was purified by a procedure that included heating, (NH₄)₂SO₄ precipitation, ion-exchange chromatography, and affinity chromatography. The purified inhibitor was shown to be a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular weight of about 10,500. It inhibited trypsin but not chymotrypsin.     

Induced Resistance to Erwinia carotovora ssp. atroseptica, Through the Treatment of Surface Wounds of Potato Tubers with Elicitors

We have investigated the ability of mixed oligogalacturonides, a cell wall hydrolysate from Phytophthora sojae Hildebrand, and chitosan oligomers to induce resistance to Erwinia carotovora ssp. atroseptica in potato tubers (cv. Pentland Squire). Natural infection by Erwinia in stored potatoes generally originates in the surface tissues which have a markedly different biochemical composition to the perimedullary tissue. We therefore investigated the effect of different elicitors in inducing resistance in 2 mm deep wounds made on the surface of potato tubers. When wounded in this way and stored at 20°C and 100% relative humidity, tubers developed a significant level of natural resistance within 24 h. When the potatoes were treated with oligogalacturonides, or Phytophthora cell wall hydrolysate at the time of wounding and challenged with inoculum 8 h later, a significant reduction in disease occurred. Treatment with the chitosan elicitor had no effect on resistance.     

Effects of Storage Temperature and Wounding on Cytokinin Levels in Potato Tubers

The level of butanol-soluble cytokinin in potato tubers (Solanumtuberosum L.) decreased greatly after harvest of the tubers,remained low during rest-period and then began to increase priorto the end of the period. In warm-stored tubers (25?C) the levelrose faster than in cold-stored ones (4?C). On the other hand,the level of water-soluble cytokinin, which was high duringthe rest-period, decreased after the rest was broken. Wounding the tubers caused an increase in butanol-soluble cytokinin.The increase in cytokinin within the first 24 hr after woundingwas smaller in warm-stored tubers than in cold-stored ones andwas decreased with increasing storage time of the tubers. Thelevel of water-soluble cytokinin decreased by wounding. Theseresults suggest that water-soluble cytokinin is a storage formand that the level of butanol-soluble cytokinin is regulatedby an interconversion between the two. (Received February 6, 1982; Accepted May 13, 1982)     

Proteinase Inhibitors in Plant Seed

Three different types of proteinase inhibitors, I, II and III, were fractionated from Japanese radish seed by repeated column chromatographies on SE- and CM-cellulose. The finally purified preparation of inhibitor III was found to be homogeneous by both chromatographic and electrophoretic analyses. All three of them strongly and stoichiometrically inhibited trypsin whereas they showed weak inhibition on other proteinases, such as chymotrypsin, Nagarse and Pronase. From nitrogen content and ultraviolet absorption spectra, each of the inhibitors I and III was confirmed to be a protein. The molecular weights of inhibitors I and III were calculated to be 8000 and 12,000, respectively. These inhibitors were stable at temperatures above 90°C in an acidic pH.     

Proteinase Inhibitors in Plant Seeds

The proteinase inhibitors I (R-I) and III (R-III) isolated from Japanese radish seed were characterized in terms of their N-terminal amino acids, amino acid composition and reacting groups. The amino acid composition of two proteins differed from each other, while histidine, methionine and tryptophan contents were all low. N-Terminal amino acids of these inhibitors determined by Edman degradation were the same; valine.

By modifying free amino groups in the inhibitors with trinitrobenzenesulfonic acid, R-III was greatly inactivated in proportion to the modification of amino groups, but the activity of R-I was not affected.

However, modification of arginyl residues of R-I by cyclohexanedione reduced its activity. These results indicate that R-I is an arginine-type and R-III is a lysine-type inhibitor.     

Transport Pathways in Sprouting Tubers of the Potato

The transport of potassium, calcium, water, and carbohydratesfrom a potato tuber to a developing sprout has been followedover an 8-week period. From the resulting balance-sheet calculationshave been made of the concentration of ions in the xylem andphloem saps entering the sprout. Similarly, the concentrationof carbohydrates in the phloem has been calculated. Predictedionic concentrations in the xylem have been confirmed from analysesof xylem exudate. The pattern of results thus obtained indicatesthe presence of a circulatory system necessitating bidirectionaltransport within the phloem. The results obtained are thereforeinconsistent with the hypothesis that a mass flow of solutesis the mechanism of translocation within the phloem     

A Note on the Determination of Alcohol in Potato Tubers

Certain samples of potato tubers have been found to containan interfering substance which is estimated as alcohol by themicro-method of Friedemann and Klass (1936) as modified by Saifi(1940).This non-alcohol material can be removed by washing the alcohol-distillatewith purified heptane. Both alcohol and the interfering non-alcohol material were shownto accumulate in potatoes held in nitrogen.     

Starch Synthesis in Developing Potato Tubers

The activities of enzymes involved in starch metabolism were measured at intervals during tuberization and the early stages of tuber growth in Solanum tubersum grown in water culture under controlled environmental conditions. Starch synthase, ADPglucose pyrophosphorylase, UDPglucose pyrophosphorylase and phosphorylase activities all increased during tuber development, the most pronounced increases occurring in the activities of ADP-glucose pyrophosphorylase and phosphorylase. The activity ratio ADPglucose pyrophosphorylase/phosphorylase was lowest in slow growing tubers and hightest in fast growing tubers. In addition, high sugar concentrations in fast growing tubers and low sugar concentrations in slow growing tubers suggested that enzyme levels might be influenced by sugar concentration. The activities of starch synthase, phosphorylase and ADPglucose pyrophosphorylase were increased 2–2.5 fold by the presence of 100 mM K⁺. It is concluded that the major enzyme changes occur as a consequence of tuber initiation and that starch accumulation is controlled, at least in part, by the activities of ADPglucose pyrophosphorylase and phosphorylase.     

Hexose Accumulation and Turgor-Sensitive Starch Synthesis in Discs Derived from Source versus Sink Potato Tubers

The net total uptake (sum of soluble and insoluble components)of the hexoses, D-glucose and D-fructose, into sink potato (Solanumtuberosum L.) storage parenchyma was biphasic with respect tosubstrate concentration. Analysis of radioactive products revealedthat the biphasic kinetics were composed of a linear, solublecomponent superimposed on saturating starch synthesis. In contrast,in source tuber tissue, there was negligible conversion of D-glucoseto starch and the shape of the kinetic was the result of a biphasicsoluble component. The uptake of D-fructose into source tissuewas linear with respect to substrate concentration. Uptake ofthe non-metabolizable glucose analogue, 3-oxymethyl-D-glucose(3-OMG), into both sink and source tissue, demonstrated biphasickinetics, indicating the presence of a carrier for glucose.The data demonstrate that in sink potato tubers, metabolismgreatly influences apparent uptake kinetics, the kinetics ofstarch synthesis masking the kinetics of hexose transport atthe plasmalemma. Uptake of L-glucose was linear with respectto substrate concentration, an observation consistent with thissugar not being recognized by a carrier. As in the case of sucrose, in sink tuber tissue the conversionof D-glucose and D-fructose to starch was sensitive to turgor,showing a marked optimum in external osmotica containing 300mol m^–3 mannitol. The mechanisms controlling turgor-sensitivestarch synthesis in the potato tuber would, therefore, appearto be common to all three sugars. Key words: Hexose (transport), partitioning, Solanum (source, sink tubers), starch synthesis     

慈菇蛋白酶抑制剂研究进展

蛋白酶抑制剂是一类能够抑制蛋白水解酶活性的物质。根据它们抑制的蛋白酶类型可分为丝氨酸、半胱氨酸、天冬氨酸、和金属蛋白酶抑制剂[1] 。由于它们能抑制昆虫肠道内以及一些病原微生物体内的蛋白酶[2～ 6 ] ,因此蛋白酶抑制剂在植物对昆虫和病原体的侵染防御系统中具有重要的作用。慈菇蛋白酶抑制剂Ａ、Ｂ是从慈菇球茎中分离纯化的双头多功能蛋白酶抑制剂 ,除了具备其他蛋白酶抑制剂在抗虫抗病方面的特点外 ,还有很多独特的优点。如 ,含量丰富、比活力高而且稳定 ;广谱性强 ;对胰蛋白酶、胰凝乳蛋白酶、激肽释放酶等多种蛋白酶有较强的抑…     

Proteinase Inhibitors in Germinating Barley Embryos

The activities of trypsin inhibitors and Aspergillus-proteinase inhibitors have been assayed in barley embryos germinating in different conditions. The Aspergillus-proteinase inhibitor activity increased about 20-fold during 6 days at 20°C both in separated embryos germinating on nutrient agar and in the embryos of undissected grains germinating on agar with or without mineral salts. Significant inhibitor activity was also present in root tips at later stages of vegetative growth. Whether any changes occurred in the molecular weight distribution of the inhibitors present in the seedlings was studied by gel filtration on Sephadex G-75; only minor changes were observed. The trypsin inhibitor activity per seedling remained roughly constant in all cultures. In gel filtration experiments all the activity appeared to be due to the inhibitor species present in resting embryos.     

The Effect of Gamma-Irradiation on the Sucrose Content in Sweet Potato Roots and Potato Tubers

The sucrose content in both potato tubers and sweet potato roots was considerably increased by gamma-irradiation. The maximum increase was achieved by an irradiation dose of 3 to 4 kGy for potatoes and 0.8 to 2 kGy for sweet potatoes. Cooling treatment (15°C, 2 weeks) for sweet potato roots also enhanced the sucrose content (almost 2 times) but was not additive to the irradiation treatment; the maximum sucrose content in irradiated sweet potato roots was in the range of 7 to 12% irrespective of the cooling treatment, depending on the variety of sweet potatoes. Irradiation made the sucrose content in the roots 2 to 4 times higher.     

Effects of 3,5-Dihalogenated-4-hydroxybenzonitriles on the Activity of Mitochondria From White Potato Tubers

Effects of the herbicide 3,5-diiodo-4-hydroxybenzonitrile (ioxynil), and its dibromo and dichloro analogs, upon the respiration of mitochondria isolated from white potato tubers (Solanum tuberosum L.) were investigated. Mitochondrial-mediated oxygen uptake was monitored polarographically with a platinum oxygen electrode.     

Effects of Gamma-irradiation on Lipid Metabolic Changes of Potato Tubers in Response to Mechanical Injury

Linolenic acid contents of glycolipids increased in irradiated potatoes during storage, accompanied by a decrease of linoleic acid. The puncturing of a potato tuber with a needle of a microsyringe caused the similar changes; the elevation of linolenic acid level and decline of linoleic acid were observed within 24 h after puncturing. Irradiation before the puncturing reduced the degree of the increase of linolenic acid in response to the mechanical injury. The rate of [¹³C]acetate incorporation into lipid fractions of irradiated tubers was smaller than that of unirradiated tubers, and polyunsaturated fatty acids (linoleic and linolenic acids) of lipid fractions were weakly labeled in irradiated tubers as compared with unirradiated ones. The results in this study indicate that irradiation retards lipid metabolism in response to mechanical injury.     

Ribonucleic Acid Changes in Germinating Potato Tubers

Abstract

The changes of the total RNA occurring during germination in potato tubers have been investigated. During germination the development of the new sprouts is accompanied by a progressive decrease of RNA. A preferential breakdown of high molecular weight RNA has been observed. Tubers deprived of the buds mantain the level of RNA of the quiescent tuber. Gibberellic acid treatment promotes the development of the sprouts, but is ineffective in inducing changes in the RNA level when supplied to isolated explants of potato tuber both germinating or deprived of buds.     

Cysteine Endopeptidase Activity in Sprouting Potato Tubers

The crude fraction extracted at pH 6.0 from sprouting potato tubers (pH 6.0 fraction) hydrolyzed casein and BAN A at pH 6.0. This pH 6.0 fraction contained not only caseinase activity but also gelatinase activity, detected by active staining of PAGE-gel with gelatin, as endopeptidases, and both activities increased during sprouting of tubers. This endopeptidase, also active on Azocolase, had an optimum pH at pH 6.0, whereas the crude fraction extracted at pH 6.0 from fresh potato tubers contained little endopeptidase activities in the whole pH range. Inhibition by monoiodoacetate or antipain indicated this endopeptidase to be a cysteine protease.     

Effects of Ambiol and 2-Chlorethylphosphonic Acid on the Content of Phytohormones in Potato Leaves and Tubers

The effects of the antioxidant Ambiol and 2-chlorethylphosphonic acid (2-CEPA) on individual concentrations and concentration ratios of phytohormones, photosynthesis and photophosphorylation rates, sucrose and starch content in tubers, and plant productivity were studied in potato (Solanum tuberosum L). Ambiol increased the ratio of indoleacetic acid (IAA) to abscisic acid (ABA), IAA/ABA, and that of zeatin (Z) and zeatin riboside (ZR) to ABA, (Z + ZR)/ABA. These effects were underlain by an increase in the content of auxins and cytokinins and a decrease in ABA. Unlike Ambiol, 2-CEPA increased the level of ABA, the effect being the most pronounced in the tubers. Ambiol increased the rates of photosynthesis and noncyclic photophosphorylation in chloroplasts isolated from potato leaves. The relation of this phenomenon to auxin and cytokinin accumulation, as well as Ambiol- and 2-CEPA-induced changes in the hormonal balance of potato tubers, carbon metabolism, and plant productivity, is discussed.     

Detection of Potato Tuber-Inducing Activity in Potato Leaves and Old Tubers

Potato tuberization is induced under short days but substancewhich triggers it is still unknown. Tuber-inducing activitywas detected in leaves and old tubers using single-node stemsegment culture in vitro as a bioassay method. The activityin leaves increased under short days, but remained almost constantunder long days. It was also found in physiologically old tubers.Anion exchange chromatography of the ethanol extract gave aneluate that exhibited strong tuber-inducing activity. Partialpurification revealed the presence of two kinds of active substances,one of which seemed to be a glycoside of the other. These substancesappear to be different from known plant hormones. (Received October 19, 1987; Accepted June 9, 1988)