Species hybrids ofDigitalis

Molecular Genetics and Genomics -     

Species hybrids ofDigitalis

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Species hybrids ofDigitalis

     

Ultrastructure ofDigitalis lanata tissue cultures

Summary The anatomy of twoDigitalis lanata tissue culture strains, S-1 and S-2, has been studied. The cardenolide accumulating cell aggregates consisted of highly vacuolated cells with very lobed nuclei in the periphery and a central part of meristematic cells. Sieve tube elements and companion cells and tracheids were observed in some of the cultures. The effect of gibberellic acid (GA₃) and SAN 9789 on the ultrastructure of the cultures was most apparent as regards the plastids and the amounts of mitochondria and ER. The content of starch seemed to be highest in the cardenolide accumulating strain S-2 grown in darkness (S-2 D) with or without GA3, but considerable amounts were also found in S-1 grown in darkness (S-1 D) with or without GA₃, which did not accumulate cardenolides. The amount of plastoglobuli was increased in S-1 by SAN treatment. It was also higher in S-2 D and S-2 D+GA₃ than in S-1 D and S-1 D+GA₃; i.e., it was high in tissues with blocked carotene synthesis. Many large plastoglobuli were also observed in apparently degenerating cells. The amount of ER seemed relatively high in cardenolide producing cultures. The amount of mitochondria was highly variable, but no correlation with cardenolide accumulation could be found.Abbreviations D dictyosome - ER endoplasmic reticulum - M mitochondrion - N nucleus - P plastid - PG plastoglobule - S starch grain - SC sieve cell - V vacuole - W cell wall - GA₃ gibberellic acid - S-1D strain S-1 cultured in darkness - S-1 L strain S-1 cultured in light - S-2 D strain S-2 cultured in darkness - S-2L8 strain S-2 previously cultured in darkness followed by 8 days in light in the present study - SAN SAN 9789 (Norflurazon) 4-chloro-5-(methylamino)-2-(,,,-trifluoro-m-tolyl)-3(2H)-pyridazinone     

Glucosidation of digitoxigenin by tissue culture ofDigitalis lanata

Summary Digitoxigenin-3-(-D-glucopyranoside) was prepared from digitoxigenin usingDigitalis lanata cells, in 36% yield. This result was achieved at a concentration of 10 g dry weight of cells per litre and 100 mg/l substrate concentration.     

The Floral Nectary ofDigitalis purpureaL., Structure and Nectar Secretion

The floral nectary of the foxglove (Digitalis purpureaL.), locatedat the base of the ovary, was examined by: scanning electronmicroscopy; quantitative bright-field microscopy via computer-aided3-D reconstruction from serial sections; morphometric procedures;transmission electron microscopy and measurement of nectar effluxunder different experimental conditions. Time-lapse video recordingvia a microscope with incident light clearly showed that thenectar escaped from the apertures of modified stomata. The volumeflux via individual stomatal apertures was 0.31±0.1 nlmin^-1; therefore only a fraction of the total number of stomataper nectary (115±8) would be sufficient to dischargethe amount of nectar reported in previous publications. Thestomatal apertures are continuous with intercellular spacestraversing the small-celled nectariferous tissue. The latteris vascularized only by phloem, whose termini consists of rowsof slender cells. These sieve-like cells are surrounded by moreor less isodiametrical sheath cells with dimensions similarto the secretory cells. Details of nectary functioning are basedon enhanced structural information, complementary data on nectardischarge after experimental manipulations and the nature ofthe effluence.Copyright 1998 Annals of Botany Company Digitalis purpureaL.; foxglove; floral nectary; (ultra-)structure; 3-D reconstruction; morphometry; nectar flow; time-lapse video recording.     

Kinetic model for biotransformation of digitoxin in plant cell suspension culture ofDigitalis lanata

Batch suspension cultures ofDigitalis lanata plant cell were performed to investigate the biotransformation of digitoxin.Digitalis lanata K3OHD plant cells were used to biotransform digitoxin into deacetyllanatoside C. A kinetic model was proposed to describe cell growth, substrate consumption, depletion of digitoxin, formation and depletion of digoxin and purpureaglycoside A, and formation of deacetyllanatoside C. The digoxin and purpureaglycoside A are intermediates of deacetyllanatoside C formation from digitoxin. Interactions between extracellular and intracellular compounds were considered. The proposed model could accurately predict cell growth, substrate consumption and product synthesis. And it can provide a useful framework for quantitative analysis of biotransformation in a plant cell culture system.     

Biotransformation of β-methyldigitoxin by cell cultures ofDigitalis lanata in airlift and stirred tank reactors

Summary Digitalis lanata cells were grown at dif-ferent dissolved-oxygen (DO) levels in 20-1 airlift reactors. A DO level of 30% saturation (using air for aeration) was found to be optimal for growth and the biotransformation ofβ-methyldigitoxin toβ-methyldigoxin. Product yield was further in-creased by using stirred tank reactors instead of the airlift reactor.