A main effects meta principal components analysis of netting effects on fruit: using apple as a model crop

To differentiate effects of netting and attribute them to crop, cultivar, planting density, climate, net type and colour, ca. 200 publications were scanned originally. Apple was chosen as a model crop due to the majority of reports, wide variation with many varieties and growing locations worldwide in the Northern and Southern hemisphere, but the results may be useful for other fruiting plants. After meeting strict selection criteria, a meta-analysis of 26 internationally published peer-reviewed articles was based on seven varieties and seventeen locations with a diverse range of climates. A novel Main Effects Meta Principal Components Analysis (ME Meta-PCA) was developed and provided unexpectedly uniform results: Location (climate), planting density and hail net (type and colour) had negligible impacts. Fruit (red) colour, most adversely affected by netting, correlated with TSS viz fruit sweetness, as often postulated in consumer studies, followed, to a smaller extent, by sugar/TSS, fruit firmness and acidity but small increase in fruit mass—i.e. maintenance of fruit quality under netting over all seven varieties (Braeburn, Gala, Elstar, Jonagold, Pinova and Fuji) examined and locations worldwide. While Jonagold and the early ripening Gala appeared suitable, unaffected and stable in the netting effects in the ME Meta-PCA, Pinova was the least suitable for cultivation under netting. Interestingly, late ripening cultivars (Braeburn and Cripps Pink) were both positively influenced by desired earlier ripening under netting. These effects on fruit quality are discussed with respect to shade adaptation under netting and countermeasures such as easy colouring mutants or reflective mulches.     

Development of semi-continuous and continuous flow bioreactors for the high level production of chloroperoxidase

Summary Continuous and semi-continuous flow bioreactors have been developed for the production of chloroperoxidase, which is secreted by the fungusCaldariomyces fumago. The semi-continuous system facilitated the harvest of mycelium-free supernatant for 200 days from a single inoculum, with enzyme levels greater than 600 mg/l during the first 80 days. The continuous flow bioreactor yielded essentially pure enzyme at the rate of 117 mg/day.     

Effect of fruiting on carbon budgets of apple tree canopies

Summary Carbon budgets were calculated from net photosynthesis and dark respiration measurements for canopies of field-grown, 3-year-old apple trees (Malus domestica Borkh.) with maximum leaf areas of 5.4 m² in a temperature-controlled Perspex tree chamber, measured in situ over 2 years (July 1988 to October 1990) by computerized infrared gas analysis using a dedicated interface and software. Net photosynthesis (Pn) and carbon assimilation per leaf area peaked at respectively 8.3 and 7.7 mol CO₂ m^–2 s^–1 in April. Net photosynthesis (Pn) and dark respiration (Rd) per tree peaked at 3.6 g CO₂ tree^–1 h^–1 (Pn) and 1.2 g CO₂ tree^–1 h^–1 (Rd), equivalent to 4.2 mol CO₂ (Pn) and 1.4 mol CO₂ (Rd) m^–2 s^–1 with maximum carbon gain per tree in August and maximum dark respiration per tree in October 1988 and 1989. In May 1990, a tree was deblossomed. Pn (per tree) of the fruiting apple tree canopy exceeded that of the non-fruiting tree by 2–2.5 fold from June to August 1990, attributed to reduced photorespiration (RI), and resulting in a 2-fold carbon gain of the fruiting over the non-fruiting tree. Dark respiration of the fruiting tree canopy progressively exceeded, with increasing sink strength of the fruit, by 51% (June–August), 1.4-fold (September) and 2-fold (October) that of the non-fruiting tree due to leaf (i. e. not fruit) respiration to provide energy (a) to produce and maintain the fruit on the tree and (b) thereafter to facilitate the later carbohydrate translocation into the woody perennial parts of the tree. The fruiting tree reached its optium carbon budget 2–4 weeks earlier (August) then the non-fruiting tree (September 1990). In the winter, the trunk respired 2–100 g CO₂ month^–1 tree^–1. These data represent the first long-term examination of the effect of fruiting without fruit removal which shows increased dark respiration and with the increase progressing as the fruit developed.     

Anatomy and Transpiration of the Avocado Inflorescence

Structure and function of the inflorescence of cv. 'Hass' and'Fuerte' avocado (Persea americana Mill.) were examined by scanningelectron microcopy (SEM) and by porometry. Sepals and petalscould not be distinguished by their position in the flower,by visual gross morphology or by microscopic surface structureand were hence designated as tepals. These tepals were arrangedin two whorls of three, followed by two whorls of three outerand three inner stamens, each opposite a tepal. The most conspicuousfeature of tepals, developing leaves and peduncles was the densecover of hair which were most frequent on the adaxial tepalsurface (925-1200 trichomes mm^-2), followed by their abaxialsurface (625-1000 mm^-2) and peduncles (375-655 mm^-2). Stomatawere absent from the adaxial surfaces of both tepal and leaves,as well as peduncles. On the tepals, abaxial stomata appearedfunctional, small (8-9 x 11-13 µm) and scarce with 2·8-3·4stomata mm^-2, i.e. very low relative to avocado leaves (350-510stomata mm^-2) or young fruit (50-75 stomata mm^-2. However, flowersincluding tepals transpired 1·2-1·3 mmol underfield conditions in Southern California (1·6-2 kPa),i.e. in excess of leaves (0·7-1·1 mmol) and peduncles(0·6-0·8 mmolH₂O m^-2 s^-1). This situation wasattributed to the few small but functional abaxial stomata onthe tepal, in contrast to 80% closed stomata and dense epicuticularwax cover in form of rodlets on young and dendritic crystalson old leaves including the guard cells, and absence of stomatafrom the peduncle.Copyright 1993, 1999 Academic Press Persea americana Mill., avocado, bioenergetics, flower, fruit, leaf, peduncle, scanning electron microscopy, stomata, transpiration, petals, sepals, tepals     

Augmentation of murine immune responses by amphotericin B.

Immunostimulant effects have been demonstrated in mice following single injections of amphotericin B or amphotericin methyl ester. Augmentation of both humoral and cell-mediated immune responses helps to explain the beneficial therapeutic effects observed in human and murine neoplasms after administration of amphotericin. Relevant to its immunological adjuvant properties, amphotericin produces striking reversible changes in murine thymus and splenic weights and in lymphoid organ histology. The chemical purity, nonimmunogenicity, and permissible toxicity of amphotericin recommend it as a model for the study of the cellular and molecular mechanisms of immunological adjuvants.     

Identification of the minimal intracellular vacuolating domain of the Helicobacter pylori vacuolating toxin

Helicobacter pylori secretes a cytotoxin (VacA) that induces the formation of large vacuoles originating from late endocytic vesicles in sensitive mammalian cells. Although evidence is accumulating that VacA is an A-B toxin, distinct A and B fragments have not been identified. To localize the putative catalytic A-fragment, we transfected HeLa cells with plasmids encoding truncated forms of VacA fused to green fluorescence protein. By analyzing truncated VacA fragments for intracellular vacuolating activity, we reduced the minimal functional domain to the amino-terminal 422 residues of VacA, which is less than one-half of the full-length protein (953 amino acids). VacA is frequently isolated as a proteolytically nicked protein of two fragments that remain noncovalently associated and retain vacuolating activity. Neither the amino-terminal 311 residue fragment (p33) nor the carboxyl-terminal 642 residue fragment (p70) of proteolytically nicked VacA are able to induce cellular vacuolation by themselves. However, co-transfection of HeLa cells with separate plasmids expressing both p33 and p70 resulted in vacuolated cells. Further analysis revealed that a minimal fragment comprising just residues 312-478 functionally complemented p33. Collectively, our results suggest a novel molecular architecture for VacA, with cytosolic localization of both fragments of nicked toxin required to mediate intracellular vacuolating activity.     

Association of Piriformospora indica with Arabidopsis thaliana roots represents a novel system to study beneficial plant–microbe interactions and involves early plant protein modifications in the endoplasmic reticulum and at the plasma membrane

Piriformospora indica , an endophytic fungus of the Sebacinaceae family, colonizes the roots of a wide variety of plant species and promotes their growth, in a manner similar to arbuscular mycorrhizal fungi. The results of the present study demonstrate that the fungus interacts also with the non-mycorrhizal host Arabidopsis thaliana and promotes its growth. The interaction is detectable by the appearance of a strong autofluorescence in the roots, followed by the colonization of root cells by fungal hyphae and the generation of chlamydospores. Promotion of root growth was detectable even before noticeable root colonization. Membrane-associated proteins from control roots and roots after cultivation with P. indica were separated by two-dimensional gel-electrophoresis and identified by electrospray ionization mass spectrometry and tandem mass spectrometry. Differences were found in the expression of glucosidase II, beta-glucosidase PYK10, two glutathione- S -transferases and several so-far uncharacterized proteins. Based on conserved domains present in the latter proteins their possible roles in plant–microbe interaction are predicted. Taken together, the present results suggest that the interaction of Arabidopsis thaliana with P. indica is a powerful model system to study beneficial plant–microbe interaction at the molecular level. Furthermore, the successful accommodation of the fungus in the root cells is preceded by protein modifications in the endoplasmatic reticulum as well as at the plasma membrane of the host.     

Deficiency of potassium but not phosphorus enhances root respiration

Root respiration of kohlrabi (Brassica oleraceavar. gongylodes) was measured non-destructivelyin vivo by infrared gas analysis of completeroot systems, using potted plants in sand culture andnutrient solutions, for six weeks under (a) nutrientsufficiency, (b) deficiency of all mineral nutrients,(c) potassium deficiency or (d) phosphorus deficiency.This was to study the adaptation to nutrient stress interms of changes in root growth, root respiration,assimilate allocation and energy requirement fornutrient uptake. Both deficiencies of phosphorus andpotassium increased the root:shoot-ratio. This wasattributed to the plants transferring a largerrelative proportion of assimilates to the roots thanto the shoots relative to nutrient-sufficient plants.Roots of nutrient-sufficient kohlrabi respired 1.7 or7.7 mg CO₂ h^–1 per g fresh or dry matter, respectively. However, potassiumdeficiency enhanced root respiration to 2.4 mgCO₂ h^–1 or 12.2 mg CO₂ h^–1 on a per g fresh or dry weight basis respectively. This originated from an additional2.6 mg glucose g^–1 dry matter h^–1 allocated to the roots and provided 50 Joule additional energy(150 versus 100 Joule g^–1 dry matter h^–1)which may become available for the proposedK⁺:H⁺ symporter for potassium uptake.     

Respiration and plasma membrane ATPase in strawberry stolons

The biochemical, physiological and anatomical properties of strawberry (Fragaria ananassa Duch.) cv. 'Cambridge Favourite' stolons were studied during growth. ATPase activity was measured, in microsomal and plasma membrane fractions, along with chlorophyll determination, in-situ photosynthesis measurements and scanning electron microscopy (SEM) and X-ray microanalysis of stolon cross-sections. Potassium-stimulated ATPase activity and proton-pumping, both together indicating the presence of plasma membrane ATPase, was greatest in the stolon tip, the tissue with the fastest growth and respiratory activity. The enzyme activity and respiration gradient from the tip of the stolon to the base was concomitant with xylem development which was more differentiated in the base than in the tip. These cross-sections also showed 30% greater amounts of calcium and potassium of the cryo-preserved basal part relative to the stolon tip. This gradient existed independent of the presence of daughter plants. A hypothesis is presented which suggests that for the long-distance longitudinal transport of nutrients this gradient between stolon tip and base is likely to be involved in stolon growth.     

Identification of the fifth axial heme ligand of chloroperoxidase

Chloroperoxidase from Caldariomyces fumago catalyzes the peroxidative chlorination of organic acceptor molecules. From a variety of spectroscopic data, it had long been thought that chloroperoxidase possessed an active site structure similar to that of cytochrome P-450cam. Resonance Raman studies conducted with isotopically substituted enzyme proved conclusively that the fifth axial ligand to the ferriprotoporphyrin IX moiety of chloroperoxidase is indeed a cysteine thiolate (Bangcharoenpaurpong, O., Champion, P. M., Hall, K. S., and Hager, L. P. (1986) Biochemistry 25, 2374-2378). In this study, Ellman's reagent, 5,5'-dithiobis(2-nitrobenzoic acid), was used to ascertain which of the 3 cysteine residues in the primary structure of chloroperoxidase serves as the fifth axial heme ligand; two of the cysteine residues were earlier shown to be involved in a disulfide linkage. Apoprotein was labeled under denaturing conditions with 5,5'-dithiobis(2-nitrobenzoic acid). A unique peptide, containing the thionitrobenzoate adduct, was isolated via reverse phase HPLC following digestion with endoproteinase Glu-C. Amino acid and Edman sequence analysis revealed the fifth axial ligand in chloroperoxidase to be cysteine 29. Under reducing and denaturing conditions, incubation of apochloroperoxidase with Ellman's reagent resulted in 3 labeled residues. Proteolysis and isolation of the labeled peptides using reverse phase HPLC and subsequent Edman sequence analysis detected and identified the thionitrobenzoate adducts of each of the three cysteinyl peptides of chloroperoxidase.