Division frequency of pea protoplasts in relation to starch accumulation

Division frequency of alginate-embedded pea (Pisum sativum var. Belman) protoplasts derived from embryonic shoot tips was studied quantitatively by image analysis in relation to starch accumulation and protoplast size. Protoplast divisions were observed from day 4 on and the number of protoplasts undergoing division increased in a stepwise manner to 70% the following days. The starch content increased rapidly during the first 3 days of culture prior to the onset of division and resulted a 4.2-fold increase in the intracellular starch area and a 3.0-fold increase (from 27% to 80%) in the number of protoplasts containing starch. Subsequent periods with rapid increases the number of dividing protoplasts were preceded by further starch accumulation. Dividing protoplasts were 33–60% smaller and contained 8–42% less starch than non-dividing protoplasts. However, calculations showed that, in the dividing protoplasts, the relative area covered by starch was 6–12% higher than in non-dividing protoplasts. These data suggest that starch accumulation precedes division of pea protoplasts.     

Protoplast liberation and regeneration in the ascomycete Hypomyces ochraceus (Pers.) Tul

A rapid and convenient method for producing protoplasts from 3 d old mycelium of the ascomycete Hypomyces ochraceus is described. The procedure involves a Helix pomatia enzyme preparation and sucrose (20%) for stabilization. Pretreatment with disulfide bond reducing agents reduced the amount of viable protoplasts. Formation of protoplasts and different stages of regeneration were observed by phase contrast microscopy. There was only one type of true regeneration from protoplasts to hyphae in 15-30% gelatine medium by direct forming a germ tube from the original protoplast. Cytological events and physiological conditions are discussed.     

Isolation of Intact and Functional Chloroplasts from Mesophyll and Bundle Sheath Protoplasts of the C(4) Plant Panicum miliaceum

A procedure is described for isolating and purifying mesophyll protoplasts and bundle sheath protoplasts of the C₄ plant Panicum miliaceum. Following enzymic digestion of leaf tissue, mesophyll protoplasts and bundle sheath protoplasts are released and purified by density centrifugation. The lower density of mesophyll protoplasts allowed rapid separation of the two protoplast types. Evidence for separation of mesophyll protoplasts and bundle sheath protoplasts (up to 95% purity) is provided from light microscopy (based on size difference in both chloroplasts and protoplasts), levels of marker enzymes in the preparations (i.e. pyruvate, Pi dikinase and phosphoenolpyruvate carboxylase for mesophyll and ribulose-1,5-bisphosphate carboxylase for bundle sheath), and differences in substrate-dependent O₂ evolution by chloroplasts isolated from protoplasts.     

Studies on the behavior of meiotic protoplasts II. Induction of a high fusion frequency in protoplasts from liliaceous plants

A method for the induction of high fusion frequencies in meioticprotoplasts of a lily and Trillium is described. Fusion wasinduced during the rapid isolation of protoplasts by quicklybringing about physical contact between protoplasts. Fused protoplastswere obtained in 50 to 90% yields from prophase cells and in30 to 60% yields from cells in later phases. Large protoplastswith more than 10 nuclei were frequently produced. During culture,meiotic development was not synchronous in these protoplasts;each multinudeate maintaining a high degree of synchrony. (Received February 28, 1973; )     

An improved procedure for the isolation and purification of protoplasts from carrot suspension culture

A procedure is reported for the rapid and highly reproducible isolation of protoplasts from carrot suspension culture. The method utilizes Onozuka R 10 cellulase which has been purified by chromatography on Sephadex G75. Protoplast isolation, using this procedure, is quantitative and complete within 1 to 1.5 h. Intact protoplasts were separated from broken ones and other cellular debris by application of a polyethylene glycol/dextran two-phase system. The protoplasts isolated in this manner lack any detectable cell wall and are greater than 95% viable when assayed using fluorescein diacetate. It is concluded that such protoplasts are highly suitable for biochemical studies.Abbreviation PCM protoplast culture medium     

Rapid separation of the chloroplast and cytoplasmic fractions from intact leaf protoplasts

Intact protoplasts are ruptured by rapid centrifugation through a narrow-aperture nylon mesh and the intact chloroplasts are then separated from the cytoplasm by sedimentation through a layer of silicone oil below the mesh. Within 6 to 8 s of starting the centrifuge, 90% of the chloroplasts are separated into the pellet fraction which contains only 10 to 15% contamination by mitochondria and peroxisomes and less than 5% contamination by soluble cytoplasm as judged by the distribution of marker enzymes. This technique should allow determination of the distribution of metabolites between the chloroplast and cytoplasmic compartments of intact protoplasts.     

Desiccation tolerance of protoplasts isolated from pea embryos

To facilitate studies of desiccation tolerance at the cellular level, a technique to isolate protoplasts from desiccation-tolerant pea (Pisum sativum L. cv. Alaska) embryos has been developed. Using FDA (fluorescein diacetate) as a probe, viability of the protoplasts was investigated before and after drying to determine whether the protoplasts could survive desiccation in a manner similar to the tissue from which they were isolated. Protoplasts were isolated from 12 h imbibed pea axes, suspended in several different sugar solutions, then dried to water contents less than 0.2 g H(2)O g(-1) DW. Protoplasts only survived drying if the rate was rapid (<2 h), while slow drying (24 h) was lethal. Maximal survival (75%) was obtained after drying protoplasts with a mixture of sucrose and raffinose, while pure sucrose and trehalose were somewhat less effective protectants. Low survival was obtained after drying protoplasts with monosaccharides and pure raffinose. Protoplasts isolated from germinated seedlings did not survive dehydration below 0.2 g H(2)O g(-1) DW. Transmission electron microscopy revealed that dried desiccation-tolerant protoplasts appeared shrunken, with folded membranes, while dried protoplasts from sensitive tissue had disrupted membranes. While isolated protoplasts maintained some of the desiccation tolerance of orthodox seeds, their inability to survive complete drying and their sensitivity to drying rate is similar to the behaviour of recalcitrant embryos.     

菌根真菌——赭丝膜伞原生质体分离与再生研究

振荡培养48h的赭丝膜伞（Cortinariusrussus）菌丝体经0．5％流基乙醇预处理后,离心法收集,以06mol／LMgSO_4作高渗稳定剂,PH5．8,采用纤维素酶、离析酶和浸解酶联合处理,在三个温度（24℃、31℃、35℃）下经11～16h反应均可获得较高的原生质体产量,最高产量达8×10~7个／g鲜重菌丝。分离得到的原生质体表现了快速的再生能力,在MMNC固体培养基上可达到20％以上的再生频率。文章较详细地研究了酶系组成、酶解温度和时间、菌丝菌龄等多个因素对C。russus原生质体分离及再生的影响。     

Isolation of Protoplasts from the Coccal Green Alga Eremosphaera viridis De Bary for Patch-clamp Measurements

A method for enzymatic isolation of protoplasts from the unicellular green alga Eremosphaera viridis for patch-clamp measurements is described. Viable protoplasts with “patch-clean” plasma membranes could only be isolated when combining high enzyme concentrations and long incubation times. In whole-cell recordings the protoplasts exhibited electrical properties similar to those measured in intact cells. Taken together with the protoplasts' ability for rapid deplasmolysis after transfer into hypotonic solution, this indicates the viability of the isolated protoplasts.     

Mechanical study of the deformation and rupture of the plasma membranes of protoplasts during osmotic expansions

Summary The stress and strain (surface tension and fractional change in area) in the plasma membrane of protoplasts isolated from rye leaves (Secale cereale L. cv Puma) were measured during osmotic expansions from isotonic into a range of more dilute solutions. The membrane surface tension increases rapidly to a maximum and then decreases slowly with some protoplasts lysing in all phases of the expansion. The maximum surface tension is greater for rapid expansions, and protoplasts lyse earlier during rapid expansion. Over the range of expansion rates investigated, the area at which lysis occurs is not strongly dependent on expansion rate. The value of the maximum tension is determined by the expansion rate and the rate at which new material is incorporated into the membrane. During osmotic expansion, protoplasts isolated from cold-acclimated plants incorporate material faster than do those from nonacclimated plants and thus incur lower membrane tensions.     

Age dependence of cowpea protoplasts for uptake of spermidine and infectibility by alfalfa mosaic virus

Cowpea protoplasts were prepared from plants of different ages and examined for their ability to take up polyamines and for their infectibility by alfalfa mosaic virus. A lag period of 20 h was necessary before the onset of rapid polyamine uptake; the occurrence of this rapid uptake depended on the age of the leaves used for protoplast preparation. The percentage of infection of cowpea protoplasts by alfalfa mosaic virus, and the amount of virus produced also depended on the age of the plants used for protoplast preparation. In contrast, the uptake of amino acids was rapid in all cowpea protoplasts tested.     

Regeneration of Plants from Protoplasts of Arabidopsis thaliana L. cv. Columbia (C24), Via Direct Embryogenesis

This report describes a protocol for the regeneration of fertileplants from mesophyll protoplasts of Arabidopsis thaliana raceColumbia (C24). Regeneration was rapid and reproducible. Theprotocol is especially novel in that a large proportion of regeneratingprotoplasts regenerated via direct somatic embryogenesis. Protoplastsisolated from in vitro-grown plants entered sustained divisionafter 3–5 d in culture medium and over a period of severaldays 6–22% of protoplasts underwent at least one celldivision. Approximately 2–16% of these protoplasts continuedto divide and after 3 weeks in culture had formed macroscopiccolonies, of which 70–80% were regular embryo-like structures.Four weeksafter release from the alginate culture matrix andtransfer to solid medium in the light, 68–88% of thesestructures had produced well-developed shoots. Shoots couldbe maintained in culture or established in peat blocks. Theregenerated plants were fertile. Key words: Arabidopsis thaliana, protoplast, regeneration, embryogenesis, dicamba     

An efficient procedure for isolation of nuclei from plant protoplasts

Summary The present communication describes an easy, efficient and rapid method for isolation of nuclei from plant protoplasts. Release of nuclei is accomplished by disruption of protoplasts in an appropriate buffer containing a very low concentration (0.01%) of the detergent Triton X-100. The pH of the nuclei isolation buffer (5.3) played a critical role in the recovery of stable nuclei in large numbers. Supplementation of buffer (10 mM MES) with spermine (0.1 mM), dithiothreitol (2.5 mM), ethylenediaminetetraacetic acid (2.5 mM) and Nad and KCl (10 mM each) improved nuclear yield and quality. With the method developed it is possible to routinely recover 95% nuclei from the protoplasts within 30 minutes. The nuclear preparations are of high purity with little detectable cytoplasmic contamination and no clumping of the nuclei. The structural integrity of the nuclei has been assessed and confirmed by Nomarski differential interference contrast optics and ultrastructural observations.     

Surface labelling of plant protoplasts with fluorochromes for discrimination of heterokaryons by microscopy and flow cytometry

Surface labelling of plant protoplasts was tested for use in mass fusion systems and heterokaryon detection. Parameters have been established for biotinylation and subsequent incubation with avidin-coupled fluorochromes. The procedure is rapid (less than 3 hours) and does not affect viability. Fusion responses were the same as with unlabelled protoplasts. From a range of fluorochromes tested, fluorescein and phycoerythrin proved best suited for detection experiments with protoplasts of both suspension and leaf origin. With this standard combination of labels, as applied in experiments with animal cells, heterokaryons from fused plant protoplasts could clearly be discriminated from other protoplasts by means of fluorescence microscopy or flow cytometry with a single combination of filters and wavelengths.     

Preparation of protoplasts from the cyanobacterium Spirulina platensis and a novel viability assay

A method is described for the isolation of protoplasts from the cyanobacterium Spirulina platensis using an elite strain (S.pl. FT 06) selected after screening. Trichomes of the cyanobacterium were treated with lysozyme (0.1%) for 28 h at room temperature in 0.03 mol l^-1 phosphate buffer (pH 6.8) with 0.5 mol l^-1 mannitol as the osmoticum. This resulted in an 80% yield of protoplasts. Cells were intact in their fine structure and viable as evidenced by a rapid and efficient viability assay using a novel mixture of fluorescein diacetate and calcofluor white.     

Isolation,culture and regeneration of protoplasts from birdsfoot trefoil (Lotus corniculatus)

A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus L. cv. Leo). Green cotyledons from in vitro grown seedlings were preplasmolyzed in CPW salts containing 13% mannitol (CPW 13 M) for 1 h prior to the enzyme treatment. The enzyme formula consisted of 2% (w/v) Onozuka Cellulase R-10, 1% (w/v) Macerase and 0.1% (w/v) Pectolyase Y-23 in CPW 13 M. This method produced high yields of viable protoplasts after purification. The procedure is reproducible and takes approximately 2.5 months from protoplast isolation to plantlet establishment in a greenhouse. More than 100 plantlets were grown in soil. Two somaclonal variants, a chimeric plant for chlorophyll production and an albino cell line, have been obtained by this procedure.     

Direct Transfer and Expression of Human GM-CSF in Tobacco Suspension Cell using Agrobacterium-Mediated Transfer System

A protocol for rapid and efficient plant regeneration from protoplasts of red cabbage was developed by a novel nurse culture method. When the protoplasts of red cabbage were cultured in modified MS medium containing various combinations of BA, NAA and 2,4-D, they did not continue dividing due to browning. However, they successfully divided and formed micro-calli at a high efficiency when they were mixed and co-cultured with those of tuber mustard at a 1:1 ratio. The presence of tuber mustard protoplasts used as nurse cells was essential for sustainable divisions and colony formation of red cabbage protoplasts. Red cabbage-like plantlets were regenerated from these protoplast-derived calli at a frequency ranging from 33 to 56% in all the experiments where three cultivars of red cabbage were tested. Over 120 protoplast-derived cabbage plants were transferred to the greenhouse, and they showed no noticeable abnormalities in morphological features. Chromosome observation revealed that all of the plants examined had the normal chromosome number of cabbage (2n = 18), suggesting that no spontaneous fusion between the two species had occurred during protoplast culture.     

Transient expression for functional gene analysis using Populus protoplasts

Despite the availability of the Populus genome sequence and the development of genetic, genomic, and transgenic approaches for its improvement, the lengthy life span of Populus and the cumbersome process required for its transformation have impeded rapid characterization of gene functions in Populus. Protoplasts provide a versatile and physiologically relevant cell system for high-throughput analysis and functional characterization of plant genes. Here, a highly efficient transient expression system using Populus mesophyll protoplasts was developed based on the following three steps. The first step involved formulating a new enzyme cocktail containing 2 % Cellulase C2605 and 0.5 % Pectinase P2611, which was shown to enable efficient large-scale isolation of homogenous Populus mesophyll protoplasts. The second step involved optimization of transfection conditions, such as the polyethylene glycol concentration and amount of plasmid DNA to ensure a >80 % transfection efficiency for Populus protoplasts. The third step involved using the Populus protoplast transient expression system to successfully determine the subcellular localizations of proteins, emulate signaling events during pathogen infection, and prepare protein extracts for Western blotting and protein–protein interaction assays. This rapid and highly efficient transient gene expression system in Populus mesophyll protoplasts will facilitate the rapid identification of gene functions and elucidation of signaling pathways in Populus.     

Formation and regeneration of protoplasts in Sclerotium rolfsii ATCC 201126

AIMS: Different cultural conditions for forming and reverting protoplasts were systematically studied to establish a rapid and efficient protocol for Sclerotium rolfsii ATCC 201126. METHODS AND RESULTS: Osmotic stabilizer, lytic enzymes and mycelial age were the main factors influencing protoplast yields. An optimized protocol involving 1-h hydrolysis of 45-h-old mycelium with Trichoderma harzianum enzymes in a 1 : 1 (w/w) biomass : enzyme ratio and 0.6 mol l-1 MgSO4 as osmotic stabilizer was designed to produce approx. 2 x 109 protoplasts per gram biomass dry weight, with 99% viability. Differences on the lytic activity between batches of commercial enzymes were clearly evidenced. Protoplast release was highly efficient showing no remaining cell wall material as witnessed by fluorescent brightener 28. Up to 26% of purified protoplasts developed into the typical filamentous form after 50 h of incubation on 0.6 mol l-1 sucrose agar media. CONCLUSIONS: The methodology herein proposed allowed a rapid, inexpensive and efficient protoplast production. Optimum yields were higher or in the order of that elsewhere reported for other S. rolfsii strains and the required lytic time was significantly shorter. Purified protoplasts successfully reverted to the filamentous morphology. SIGNIFICANCE AND IMPACT OF THE STUDY: The present research reports the former protocol for the isolation and reversion of protoplasts in S. rolfsii ATCC 201126 providing key factors to ensure optimum results. In addition, the described procedure constitutes a starting point for downstream genetic manipulation.     

Freezing behavior of free protoplasts of winter rye

Free protoplasts prepared from the epicotyls of nonhardened rye seedlings were subjected to fast and slow freezing on a microscope-adapted thermoelectric stage. During rapid freezing to ?12 °C, ice formation occurred inside the protoplasts causing lethal disruption of cell and membrane organization. Under slow freezing to ?12 °C, ice formation occurred outside the protoplast with accompanying dehydration and contraction of the protoplast. Complete rehydration and recovery of the protoplasts occurred upon thawing after slow freezing. Free protoplasts therefore afford a new system for the study of mechanisms of plant cell freezing injury and resistance free of the complications presented by a cell wall.