Staining Scab Actinomyces in Potato Tuber Tissues

Actinomyces hyphae imbedded in the middle lamellae of potato tuber cells may be stained in sections by the use of a modified Gram's stain. The modifications are: a very strong (5%) solution of crystal violet in anilin oil; a 24-hour exposure to both the dye and the iodine solution; and a slow decolorization in absolute alcohol until no more color flows.     

Nitric Oxide Induces Phytoalexin Accumulation in Potato Tuber Tissues

We investigated whether nitric oxide (NO) radical could inducephytoalexin production. Treatment of potato tuber tissues with1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)-1-triazene (NOC-18), anNO-releasing compound, induced the accumulation of the potatophytoalexin rishitin. This induction was inhibited by carboxy-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide(carboxy-PTIO), an NO-specific scavenger, or by Tiron, a radicalscavenger, suggesting a phytoalexin inducing activity for NO. (Received December 7, 1995; Accepted January 4, 1996)     

Gibberellic Acid Activates Chromatin-bound DNA-dependent RNA Polymerase in Wounded Potato Tuber Tissue

Chromatin-bound DNA-dependent RNA polymerases react upon wounding of white potato tuber tissues with an increase in activity, which is additionally enhanced to 300% in the presence of 0.1 micromolar gibberellic acid (GA₃). 2,4-Dichlorophenoxyacetic acid is only weakly effective and indoleacetic acid not at all. Wounding and treatment with GA₃ affect template availability of chromatin only slightly. The hormone has no effect on chromatin-bound RNA polymerases, if added in vitro.     

Influence of Ageing and Abscisic Acid on Potassium Uptake by Potato Tuber Tissues

The potassium uptake by potato tuber discs tissues freshly cut and after 24 h of ageing in the presence or not of abscisic acid was investigated. Uptake kinetics revealed a biphasic dependence on external K⁺ concentrations. At concentration less than 10 mM, uptake was mediated by a saturable component and a linear component became apparent at higher concentrations. At low K⁺ concentrations (lmM), the capacity of K⁺ uptake diminished by 2 times after ageing. Treatment of tissues with ABA increased the rate of K⁺ uptake. In both fresh and aged tissues the uptake was strongly enhanced by fusicoccin and decreased by several metabolic inhibitors and ATPase inhibitors, underlying the active nature of uptake and suggesting the involvement of a plasmalemma H⁺-ATPase in K⁺ transport system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phosphorylation of Chromosomal Proteins Changes during the Development of Crown Gall Tumors

Crown gall tumors were initiated on potato tuber nurse tissueby Agrobacterium tumefaciens, strain C58. Tumorous protuberancesappeared some 5–8 days after infection and grew to knob-liketumors in 3–5 weeks, after which proliferation diminishedcontinuously and then ceased in old tumors. Synthesis of RNAincreased dramatically in growing tumors as did the activityof both chromatin-bound DNA-dependent RNA polymerases I andII. Chromatin-bound protein kinases accepting endogenous proteins,phosvitin, casein or histones were activated concomitantly,leading to higher phosphorylation rates of chromatin proteinsduring tumor development. With the transition of a normal, woundedcell into a transformed cell, the chromosomal protein patternchanged and then remained unchanged throughout tumor growthand senescence. In contrast, the phosphorylation pattern ofthese proteins was highly stage-specific. ¹Dedicated to our friend and colleague, late Professor Dr. R.K. Tripathi (Pant-nagar University, Nainital, India). (Received January 11, 1984; Accepted July 17, 1984)     

Analysis of the Components Released from Potato Tuber Tissues during Maceration by Pectolytic Enzymes

Endo-pectin lyase and endo-polygalacturonase of Aspergillus japonicus attack the middle lamella of plant tissue and cause tissue maceration. Galacturonides, neutral sugars, and proteins were released from potato tuber tissues during maceration by both purified enzymes. These three components accounted for 92% of the soluble products. The neutral sugars released were rhamnose, arabinose, and galactose with a molar ratio of 1:3:15. They were covalently linked to galacturonides. Over 85% of the galacturonides released by the enzymes were short chain products, which indicated that a large portion of the main chain of pectic substances is a homogalacturonan. The results of chromatography on columns of Sephadex G-100 and DEAE-cellulose suggested that a protein component may be attached to pectic substances. This protein did not contain hydroxyproline and, therefore, was different from the cell wall structural glycoprotein.     

Phosphoproteomic Analysis of Potato Tuber Reveals a Possible Correlation Between Phosphorylation Site Occupancy and Protein Attributes

Plant Molecular Biology Reporter - Protein phosphorylation is a critical post-translational modification in all aspects of plant biology. The position of the phosphorylated site is an essential...     

Characterization and Translation of Poly(A)+RNA from Wounded and Crown Gall Tissues of Potato Tubers

Poly(A)⁺ and poly(A)^–RNA from wounded potato tuber tissuesand crown gall tumors were separated from total RNA by oligodeoxythymidylicacid-cellulose affinity chromatography. The poly(A)⁺RNA wascharacterized by sucrose density gradient centrifugation, hybridizationwith ³(H)polyuridylic acid [Poly(U)] and in vitro translationin a rabbit reticulocyte lysate system. The tumor poly(A)⁺RNAwas a heterodisperse mixture from 3.5S to 35S. Upon poly(U)hybridization of the gradient fractions two major hybridizationpeaks at 7S and 21S and two peaks at 11S and 16S appeared. Inan in vitro translation system the poly(A)⁺RNA programmed thesynthesis of 23 different polypeptides of 9,000 to 79,800 daltonsmolecular weight as determined by SDS-polyacrylamide gel electrophoresis.The 21S poly(A)+RNA was about 5 times more active in in vitroprotein synthesis than the 7S poly(A)⁺RNA. The poly(A)⁺RNA from wounded tissues was also heterodisperse(from 4.5S to 31S) with a modal peak at 18S. This RNA codedfor at least 28 polypeptides, which were different from thoseof crown gall tumor tissues. On a per unit poly(A)⁺RNA basis the tumor RNA was slightly moreactive in translation than that from wounded tissues. The translationof tumor poly(A)⁺RNA was completely blocked by 0.5 mM 7-methylguanosine5'-phosphate, but not by 7-methylguanosine, suggesting the presenceof a 5'-cap structure. (Received May 15, 1982; Accepted June 30, 1982)     

Physiological Gradients in the Potato Tuber

The distribution of the major cations and anions, together with citric acid, malic acid and iron, has been studied in tubers of Solanum tuberosum cv. Golden Wonder, by analysis of longitudinal cores divided into 16 equal cylindrical sections. In immature daughter tubers the constituents studied were evenly distributed along the tuber, but in mature tubers a considerable polarity had developed. The concentrations of potassium, phosphorus and citric acid each rose from the heel to the rose end of the tuber. Iron showed a gradient in the opposite direction. These gradients were maintained in sprouting tubers, and although after 25 days the levels of these constituents were reduced, the patterns of distribution were unchanged. In the exhausted mother tubers all these constituents were much depleted and only potassium exhibited any pattern of polar distribution. Malic acid was barely detectable at any stage, and calcium, sodium, magnesium, chloride, sulphate and nitrate were always at low levels and showed no polarity of distribution. At each developmental stage potassium was correlated with the difference in electrical potential measured between cells at points across the tuber. A close correlation was apparent between potassium and citric acid content in young, mature and sprouting tubers. In all stages a considerable discrepancy existed between total anions and total cations and this was attributed to the presence of organic acids other than citric acid.     

Respiration and Carbohydrate Metabolisms of Potato Tuber

When a potato tuber is cut into slices, the activity of dehydrogenase system linked to DPN decreases but the activities of tyrosinase system and G-6-P dehydrogenase increase in the slices. Accompanying the changes of these enzymatic activities, the metabolic pathway in the slices turns from glycolytic path to pentose phosphate path. Tyrosinase oxidizes phenols which are formed from an intermediate of the pentose phosphate path, sedo-heptulose via shikimate as in microorganisms, resulting in increase in the oxygen uptake of the slices. It seems impossible to play a role as a terminal oxidase linked to diphosphopyridine nucleotide.     

Aging and Mitochondrial Development in Potato Tuber Tissue

Respiratory activity of mitochondria isolated from fresh and aged potato tuber tissue has been determined. No significant change in activity of the particles (expressed per unit N) was observed as a result of aging. However, the yield of mitochondrial material increased with aging. It has been suggested that the commonly observed stimulation of respiration that accompanies aging of potato tissue can be attributed largely to an inerease in the mitochondrial population rather than to a stimulation of the particles per se, and that this increase results from a fission of pre-existing mitochondria. The respiratory activity of mitochondria isolated from unaged tissue was found to decline following storage of the tubers in the cold for extended periods. This decline was attributed to a loss of cristae structure in the particles, as observed microscopically. The possibility that this reduction in structural organization might be associated with changes in the state of dormancy of the tissue was considered.     

Regeneration of Tissues in Wounded Stems: A Quantitative Study

When a dicotyledonous stem is wounded by longitudinally splittinga young internode into halves, cells near the cut surface proliferateto form a callus within which vascular tissues differentiateand tend to restore a vascular cylinder in each half. Threephases of regeneration after wounding were identified and quantifiedin stems of three Solanaceous species. (1) In an initial ‘lag’phase, lasting about 2 d, neither cell division nor enlargementwere detected, but mitotic figures were observed within about300 µm of the cut surface. (2) Throughout a second, ‘division’phase, from about days 2–10, cell division and enlargementoccurred. Both were initiated mainly in the two cell layersnearest the surface. A mass of callus formed, with new cellwalls mostly parallel to the surface. Cell enlargement laggedbehind cell division for the first few days, so that mean radialcell diameter decreased until day 6, thereafter remaining almostconstant at 30–40 µm. Towards the end of this phase,mitoses ceased within the callus except in the positions ofthe future vascular and cork cambia, where radial cell diameterfell towards a constant 15–20 µm. (3) During a third,‘differentiation’ phase, cell division was restrictedto the cambial zones, and derivatives differentiated into cork,phloem or xylem according to position. The rate of increasein cell number per transect was 1.5–2.0 cells d^–1,of which more than half was xylem. Capsicum annuum L., sweet pepper, Lycopersicon esculentum Mill., tomato, cambium, cell division, differentiation, regeneration, wounding of stems, xylem     

Plastid and Nuclear DNA in Potato Tuber Tissue 7

On exposure to light the outer parenchyma layers of mature potatobecame green as amyloplasts are converted to chloroamyloplasts.This tissue was sampled during greening, and analysed for nuclearand plastid DNA content. There was an increase in the proportionof plastid DNA in total DNA from 15% in white tuber tissue to22% in greened tissue, while the nuclear ploidy distributionand average nuclear ploidy was similar in both. Key words: Solatium tuberosum, greening, amyloplast     

Stimulation of Potassium Uptake by Abscisic Acid in Potato Tuber Tissues. Relation with H+ and Ca2+ Fluxes

Previous results with potato tuber discs showed that a treatment with abscisic acid stimulated K⁺ uptake. In this investigation, we determine the relationship between increased K' uptake and H⁺extrusion, and Ca²⁺ fluxes by treating tissues with specific Ca²⁺ channel blocker (La³⁺), calmodulin (CaM) inhibitors (chlorpromazine and W₇), and with Ca²⁺ ionophore (A23187). K⁺ uptake increased with increasing external pH whether tissues were treated with ABA or not. Treatment of tissues with La³⁺ inhibited K⁺ uptake, whereas CaM inhibitors have no effect. By contrast ABA and A23187 produced a synergistic effect, suggesting that ABA may act in part, on K⁺ uptake, like a Ca²⁺ agonist, in accord with Huddart's hypothesis. This revised version was published online in July 2006 with corrections to the Cover Date.