Growth Of Protoplasts Research Articles

Effects of Salts on Helical Protoplast-Callose-Fiber Formation and Cell Division in Leaf Protoplast Culture of Arabidopsis thaliana: Ultrastructure of PCF Using Transmission Electron Microscopy

Effects of four salts addition (10-200 mM), NaCl, KCl, MgCl2, and CaCl2 were examined on the growth of protoplasts and formation of helical 1.5 mm long, protoplast-callose-fibers (PCF) in Arabidopsis thaliana liquid leaf protoplast cultures. The basal medium was Murashige and Skoog’s medium containing 1 μM 2,4-dichlorophenoxyacetic acid and 0.1 μM benzyladenine, 3% sucrose, and 0.4 M mannitol. The protoplast division was highly stimulated by the addition of 50 mM Ca2+ ion but was totally inhibited by 50 mM Mg2+ ion. Inhibition by K+ and Na+ ions was in-between. By contrast, PCF formation, whose numbers were counted under a fluorescence inverted microscope after Aniline Blue staining for β-1,3-glucan (callose), was stimulated by both K+ and Ca2+ ions but inhibited by Mg2+ ion. After selecting Arabidopsis PCF using a micromanipulator, the sub-fibril ultrastructure was examined by transmission electron microscopy (TEM). The PCFs of Betula platyphylla and Larix leptolepis, cultured with 200 mM Ca2+ and 50 mM Mg2+ ions, respectively, after long-term storage and rehydration, were examined by TEM. The effects of different factors were discussed on PCF formation and sub-structures in different herbaceous and tree plant species.

The reproduction of gram-negative protoplasts and the influence of environmental conditions on this process

Bacterial protoplasts are known to reproduce independently of canonical molecular biological processes. Although their reproduction is thought to be influenced by environmental conditions, the growth of protoplasts in their natural habitat has never been empirically studied. Here, we studied the life cycle of protoplasts in their native environment. Contrary to the previous perception that protoplasts reproduce in an erratic manner, cells in our study reproduced in a defined sequence of steps, always leading to viable daughter cells. Their reproduction can be explained by an interplay between intracellular metabolism, the physicochemical properties of cell constituents, and the nature of cations in the growth media. The efficiency of reproduction is determined by the environmental conditions. Under favorable environmental conditions, protoplasts reproduce with nearly similar efficiency to cells that possess a cell wall. In short, here we demonstrate the simplest method of cellular reproduction and the influence of environmental conditions on this process.

Strong Allelopathic Activity in Purple Leaves of Transgenic Spiraea cantoniensis Containing Cyanidin 3-Glucoside Assayed by the Protoplast Co-culture Method with Digital Image Analysis

The protoplast co-culture method with digital image analysis (DIA-PP method), was used for in vitro bioassay of allelopathic activity in the leaves of in vitro cultured plants of Spiraea cantoniensis. Purple leaves of transgenic S. cantoniensis, containing an anthocyanin, cyanidin 3-glucoside showed strong inhibitory allelopathic activity, 100% inhibition of recipient lettuce protoplast division by 80 × 103 mL-1 of co-cultured protoplasts, while green leaves of non-transgenic S. cantoniensis showed only 20% inhibition. Cyanidin 3-glucoside which inhibited lettuce protoplast division 80% at 100 µM was evaluated as an allelochemical of transgenic S. cantoniensis. Inhibition was stronger at the cell division stage of lettuce protoplast growth than that at the other stages, i.e., cell wall formation stage and yellow pigment accumulation stage. The results were discussed comparatively with the strong inhibitory activity of non-transgenic S. thunbergii and other allelopathic plant species containing different anthocyanin or carotenoid pigments as putative allelochemicals.

Plant regeneration from leaf mesophyll derived protoplasts of cassava (Manihot esculenta Crantz).

A high yield of isolated protoplast and reliable regeneration system are prerequisite for successful somatic hybridization and genome editing research. However, reproducible plant regeneration from protoplasts remains a bottleneck for many crops, including cassava. We evaluated several factors that influence isolation of viable protoplasts form leaf mesophyll, induction of embryogenic calli, and regeneration of plants in three cassava cultivars; Muchericheri, TMS60444 and Karibuni. A relatively higher protoplast yield was obtained with enzyme mixture containing 5 g/L Macerozyme and 10 g/L cellulase. Muchericheri recorded relatively higher protoplast yield of 20.50±0.50×106 whereas TMS60444 (10.25±0.25×106) had the least protoplast yield in 10 g/L cellulase and 4 g/L cellulase. Freshly isolated protoplast cells were plated on callus induction medium (CIM) solid medium containing MS basal salt, 60 g/L D-glucose, 30 g/L sucrose, B5 vitamins, 100 mg/L myo-inositol, 0.5 mg/L copper sulphate, 100 mg/L casein hydrolysate, 4.55 g/L mannitol, 0.1 g/L MES, 10 mg/L picloram and 3 g/L gelrite to induce protoplast growth and development. The three cultivars reached colony formation but no further development was observed in this culture method. Protoplast growth and development was further evaluated in suspension culture using varying cell densities (1, 2 and 3× 105 p/mL). Development with highest number of minicalli was observed in cell density of 3× 105 p/mL. Minicalli obtained were cultured on CIM supplemented with 10mg/L picloram. Callus induction was observed in all cell densities with the cultivars. Highest somatic embryogenesis was observed in 2× 105 p/ml while no somatic embryogenesis was observed in cell density of 1×105 p/mL. Somatic embryos were matured in EMM medium supplemented with 1 mg/L BAP, 0.02 mg/L NAA and 1.5 mg/L GA3 then germinated in hormone free medium for plant regeneration. This protocol which used simple mixture of commercial enzymes is highly reproducible and can be applied in biotechnology research on cassava.

Establishment of an Efficient Protoplast Regeneration and Transfection Protocol for Field Cress (Lepidium campestre).

Field cress (Lepidium campestre) is a potential oilseed crop that has been under domestication in recent decades. CRISPR/Cas9 is a powerful tool for rapid trait improvement and gene characterization and for generating transgene-free mutants using protoplast transfection system. However, protoplast regeneration remains challenging for many plant species. Here we report an efficient protoplast regeneration and transfection protocol for field cress. Important factors such as type of basal media, type/combination of plant growth regulators, and culture duration on different media were optimized. Among the basal media tested, Nitsch was the best for protoplast growth in MI and MII media. For cell wall formation during the early stage of protoplast growth, relatively high auxin concentrations (0.5 mg L−1 NAA and 2,4-D), without addition of cytokinin was preferred for maintaining protoplast viability. After cell wall formation, 1.1 mg L−1 TDZ combined with either 0.05 mg L−1 NAA or 2,4-D was found to efficiently promote protoplast growth. On solid shoot induction medium, 1.1 mg L−1 TDZ without any auxin resulted in over 80% shoot generation frequency. A longer culture duration in MI medium would inhibit protoplast growth, while a longer culture duration in MII medium significantly delayed shoot formation. Using this optimized protoplast regeneration protocol, we have established an efficient PEG-mediated transfection protocol using a vector harboring the GFP gene, with transfection efficiencies of 50–80%. This efficient protoplast protocol would facilitate further genetic improvement of field cress via genome editing, and be beneficial to development of protoplast regeneration protocols for related plant species.

Allelopathic activities of three carotenoids, neoxanthin, crocin and β-carotene, assayed using protoplast co-culture method with digital image analysis.

Allelopathic activities of three carotenoids of a natural pigment group, neoxanthin, crocin and β-carotene, were assayed by the protoplast co-culture method with digital image analysis (DIA-PP method). Effects on three different growth stages of lettuce protoplasts, i.e., cell wall formation, cell division, and yellow pigment accumulation, were investigated using 96-well culture plates. Cell division was inhibited 65-95% by all three carotenoids at 33-100 µM. Inhibition of cell division stage was stronger than at the cell wall formation stage in neoxanthin, and the water-soluble carotenoid, crocin, whose yellow pigment was incorporated into the vacuole of lettuce protoplasts. Neoxanthin at 33 µM and crocin at higher than 100 µM inhibited more than 100% of the yellow pigment accumulation. By contrast, at low concentrations (0.01-1 µM) β-carotene stimulated growth at the cell division stage. At high concentrations of β-carotene (100-500 µM), inhibition was prominent at all three stages, and also in neighboring wells of zero control, which suggested emission of a volatile compound by β-carotene. They were compared with the report of the volatile compound, tulipalin A. Differences in patterns of inhibition of carotenoids on lettuce protoplast growth were compared with reports of another natural pigment, anthocyanin, and anthocyanin-containing red callus cultured in the light, and with that of neoxanthin-containing yellow callus cultured in the dark.

Evaluation of Isoflavones as Allelochemicals with Strong Allelopathic Activities of Kudzu Using Protoplast Co-Culture Method with Digital Image Analysis

The inhibitory allelopathic activity of Pueraria montana (Kudzu), and activities of two putative allelochemical isoflavones, puerarin and daidzein, were evaluated using the protoplast co-culture method with digital image analysis using lettuce as a recipient (DIA-PP method). Cotyledon protoplasts of Kudzu were isolated using Cellulase R10 and Driselase 20 in 0.6 M mannitol solution. Optimal hormonal condition and density for growth of Kudzu protoplasts were surveyed. Medium for co-culture of Kudzu or isoflavones with lettuce protoplasts was 50 μl liquid MS basal medium containing 1 μM 2,4-dichlorophenoxyacetic acid, 0.1 μM benzyladenine, 3% sucrose, and 0.4 M or 0.6 M mannitol. Protoplast division of lettuce was strongly inhibited by Kudzu at a low density (104/ml). Slightly less inhibition by Kudzu on cell wall formation and yellow pigment accumulation stages of lettuce growth was also observed. Puerarin did not inhibit the growth of lettuce protoplasts at three growth stages but slightly stimulated growth at high concentrations. By contrast, daidzein, aglycon of puerarin, inhibited growth at three stages of lettuce protoplast growth and strongly inhibited cell division at 100 μM. Daidzein might be one cause of the strong inhibitory allelopathic activity of Kudzu. Grade of inhibitory activities was compared with that of other allelopathic plants including an invader plant and their allelochemicals studied using the DIA-PP method.

Strong Allelopathic Activities of Leaves and Cultured Cells of <i>Spiraea thunbergii</i> Assayed by the Protoplast Co-Culture Method with Digital Image Analysis: Evaluation of <i>Cis</i>- and <i>Trans</i>-Cinnamic Acid as Allelochemicals

The inhibitory allelopathic activities of leaves and leaf-origin suspension cultured cells of Spiraea thunbergii, and putative allelochemicals, cis- and trans-cinnamic acid, were investigated by the protoplast co-culture method with digital image analysis (DIA-PP method) using lettuce as a recipient. The optimal conditions of 2,4-dichlorophenoxyacetic acid (2,4-D) and benzyladenine (BA) for the cell division of S. thunbergii protoplasts were first examined using 50 μL liquid MS basal medium containing 3% sucrose, and 0.8 M mannitol in a 96-well culture plate. The hormonal condition for co-culture, 1 μM 2,4-D plus 0.1 μM BA, which was optimal for lettuce protoplast growth, was sub-optimal for S. thunbergii protoplasts. Effects of co-culture on the three stages of lettuce protoplast growth, i.e., cell wall formation, cell division, and yellow pigment accumulation, were examined. Protoplasts of leaf and suspension cells of S. thunbergii strongly inhibited lettuce protoplast growth at the cell division stage (100% inhibition at 80 - 100 × 103 mL-1), but not so much at the other two stages. Both cis- and trans-cinnamic acid, showed the strongest inhibition at the cell wall formation stage, and 100% inhibition at the cell division stage at 100 μM. These results were compared with those obtained in a lettuce seedling growth test, using different allelopathic plants, and their allelochemicals were studied by the DIA-PP method.

Application of the protoplast co-culture method for evaluation of allelopathic activities of volatile compounds, safranal and tulipalin A

The effects of two plant volatile compounds (VOCs), safranal and tulipalin A were investigated using the protoplast method with digital image analysis, which was developed to investigate allelopathic activities of plants at the cellular level in a 50 μL liquid medium. Both VOCs showed inhibition on lettuce protoplasts growth at all three stages, i.e., the cell wall formation stage, the cell division stage, and the yellow colour accumulation stage. Among the three stages of protoplast growth, differences of inhibition patterns were observed. Inhibitions at the cell wall formation stage were stronger than those at the latter two stages in both VOCs. Tulipalin A showed higher inhibitory activity (total inhibition at 100 μM) than that of safranal (44% inhibition at 1 mM) at cell division stage. They were also compared with the direct exposure method in an enclosed vial using germinated lettuce seedlings, which was developed to investigate allelopathic activities of VOCs at plant level. Tulipalin A showed less inhibitory activity on radicle growth of lettuce, than that of safranal reported. Inhibition on hypocotyl growth was stronger than that on radicle in both VOCs. The causes of the differences between two VOCs and two bioassay methods, and the application of the protoplast method, were discussed for clarifying the contribution of VOCs as allelochemicals at cellular level.

Optimization of Polyethylene Glycol-Mediated Transformation of the Pepper Anthracnose Pathogen Colletotrichum scovillei to Develop an Applied Genomics Approach.

Colletotrichum acutatum is a species complex responsible for anthracnose disease in a wide range of host plants. Strain C. acutatum KC05, which was previously isolated from an infected pepper in Gangwon Province of South Korea, was reidentified as C. scovillei using combined sequence analyses of multiple genes. As a prerequisite for understanding the pathogenic development of the pepper anthracnose pathogen, we optimized the transformation system of C. scovillei KC05. Protoplast generation from young hyphae of KC05 was optimal in an enzymatic digestion using a combined treatment of 2% lysing enzyme and 0.8% driselase in 1 M NH4Cl for 3 h incubation. Prolonged incubation for more than 3 h decreased protoplast yields. Protoplast growth of KC05 was completely inhibited for 4 days on regeneration media containing 200 μg/ml hygromycin B, indicating the viability of this antibiotic as a selection marker. To evaluate transformation efficiency, we tested polyethylene glycol-mediated protoplast transformation of KC05 using 19 different loci found throughout 10 (of 27) scaffolds, covering approximately 84.1% of the entire genome. PCR screening showed that the average transformation efficiency was about 17.1% per 100 colonies. Southern blot analyses revealed that at least one transformant per locus had single copy integration of PCR-screened positive transformants. Our results provide valuable information for a functional genomics approach to the pepper anthracnose pathogen C. scovillei.

An Evolutionarily Conserved Receptor-like Kinases Signaling Module Controls Cell Wall Integrity During Tip Growth.

Rooting cells and pollen tubes-key adaptative innovations that evolved during the colonization and subsequent radiation of plants on land-expand by tip growth. Tip growth relies on a tight coordination between the protoplast growth and the synthesis/remodeling of the external cell wall. In root hairs and pollen tubes of the seed plant Arabidopsis thaliana, cell wall integrity (CWI) mechanisms monitor this coordination through the Malectin-like receptor kinases (MLRs), such as AtANXUR1 and AtFERONIA, that act upstream of the AtMARIS PTI1-like kinase. Here, we show that rhizoid growth in the early diverging plant, Marchantia polymorpha, is also controlled by an MLR and PTI1-like signaling module. Rhizoids, root hairs, and pollen tubes respond similarly to disruption of MLR and PTI1-like encoding genes. Thus, the MLR and PTI1-like signaling module that controls CWI during tip growth is conserved between M.polymorpha and A.thaliana, suggesting that it was active in the common ancestor of land plants.

Lipid determinants of endocytosis and exocytosis in budding yeast

Cells maintain physicochemical characteristics of membranes in order to allow for proper function of membrane-associated cellular processes, such as endocytosis and exocytosis. To investigate the interplay between membrane properties and biological processes, we applied lipid engineering approaches that allowed for systematic manipulation of fatty acid unsaturation and sterol biosynthesis, the main regulators of membrane fluidity. In combination with electrophysiological membrane capacitance measurements, we were able to study the dependence of the endo- and exocytic activity of Saccharomyces cerevisiae on membrane lipid composition in vivo. We found that a strong decrease in the cell's total ergosterol content leads to a severely reduced frequency of vesicle fission (endocytosis), whereas the exocytic activity remained largely unaffected. In contrast, increased lipid saturation lowered both endocytic and the exocytic activity, with the former being more severely affected. We were able to correlate the decreased ratio of endocytic/exocytic frequencies (fendo/fexo) upon lipid perturbation with the growth of yeast protoplasts, which is based on a surface enlargement resulting from a net excess of exocytic over endocytic flux. Experiments using clathrin-deficient mutants confirm a correlation between reduced endocytic activity and increased size of intact walled cells, as well as accelerated protoplast growth. These data show that lipid composition is intimately tied to membrane trafficking in yeast cells and suggest that endocytosis is particularly dependent on the lipid-defined properties of cell membrane.

Evaluation of an Anthocyanin, Cyanidin 3,5-di-O-glucoside, as an Allelochemical in Red Callus of a Mangrove Sonneratia ovata, Using Protoplast Co-Culture Bioassay Method with Digital Image Analysis

protoplasts to examine the allelopathic activities. Protoplasts were isolated with Cellulase R10 and Driselase 20 in 0.6 M mannitol solution and purified by density gradient centrifugation on 0.6 M sucrose. Protoplasts were co-cultured in 50 μL of liquid Murashige and Skoog’s (MS) basal medium containing 1 μM 2,4-dichlorophenoxyacetic acid and 0.1 μM benzyladenine and 0.6 M mannitol solution in a 96-well culture plate. Protoplast density ranged from 5 × 103/mL to 105/mL. Cell division of lettuce protoplasts was strongly inhibited by addition of S. ovata protoplasts, and non-spherical cell enlargement was slightly inhibited. By contrast, digital image analysis of scanned 96-well culture platesrevealed no inhibition in accumulation of yellow color in lettuce protoplasts. An anthocyanin, cyanidin 3,5-di-O-glucoside (cyanin), was identified and its content in the red callus was ca. 1 mM of fresh weight. The effects of cyanin on the growth of lettuce protoplasts at three stages were similar to those of red S. ovata protoplasts. From these results, cyanin was most likely the allelochemical contained in red callus of S. ovata. The allelopathic activity of cyanin was compared with that of other putative allelochemicals in several plant materials, using the protoplast co-culture method with digital image analysis.

Evaluation of Allelochemicals, Abscisic Acid and Coumarin, in Leaf-Origin Suspension Cultured Cells of <i>Prunus yedoensis</i> Using Protoplast Co-Culture Bioassay Method

Dried leaves of Prunus yedoensis and P. lannesiana (50 mg) showed strong inhibitory allelopathic activities, e.g., more than 97% growth inhibition of lettuce seedling using the sandwich method. Similarly, among suspension cultures induced from leaves and peduncles of two Prunus species, we found the strongest inhibitory allelopathic activities of protoplasts of leaf-origin suspension cells of P. yedoensis, when the protoplast co-culture method for bioassay of allelopathy was applied with lettuce as a recipient plant. Effects of two putative allelochemicals, abscisic acid and coumarin, on both protoplast cultures of lettuce and P. yedoensis were investigated. Coumarin inhibited the growth of lettuce protoplasts from low concentrations, while abscisic acid stimulated. Abscisic acid inhibited the protoplast growth of P. yedoensis from low concentrations, while coumarin did not, but inhibited only at a high concentration (1 mM). Contents of abscisic acid in protoplasts were measured using small scale purification and Enzyme Linked Immno Sorbent Assay, and contents of coumarin in leaf-origin susepension cells of P. yedoensis were measured using Gas Chromatography-Mass Spectrometry. Coumarin was more likely the allelochemical causing the strong inhibitory allelopathic activities of P. yedoensis in the protoplast co-culture bioassay. Effectiveness of the protoplast co-culture bioassay method of allelopathy was discussed.

Cellular Calcium Distribution Modulates the Growth of Callus and Protoplasts of Halophyte Mangrove Plant, Avicennia Alba - an X-ray Microanalysis

Two cultured cell lines were developed from cotyledons of a halophyte mangrove, Avicennia alba.In the high-Ca callus line, which was sub-cultured in amodified amino acid medium containing 3 mM CaCl2, growth of calluses and their protoplasts were both inhibited by low concentrations of CaCl2 in the culture medium. Removal of Ca2+ from the culture medium stimulated callus growth and the calluses could be sub-cultured without CaCl2 (low-Ca callus line). The intra- (cytoplasmic matrix and vacuole) and extra- (cell wall) cellular concentrations of elements, i.e., [Ca], [K], [Cl], [Na], [Mg], [P] and [S] were investigated using quantitative X-ray microanalysis of cryosections of calluses from bothcell lines. [Ca] was high in the cytoplasmic matrix and cell wall of the high-Ca line. [Ca] was lowered in the low-Calineinall cell compartments, though still detected. Ca-containing electron-dense precipitates were accumulated in the middle lamella of cell walls in resin-embedded sections of the high-Ca line. CaCl2 in the medium stimulated protoplast growth only in the low-Caline. These results suggested that a low cellular [Ca] is needed for protoplasts growth of A. alba. The importance of cellular [Ca] for the growth of halophilic mangrove plant cells was discussed.

In vitro bioassay of allelopathy of Arabidopsis thaliana by sandwich method and protoplast co-culture method with digital image analysis.

We examined the allelopathic activities of Arabidopsis thaliana, ecotype Columbia by two in vitro methods. The effect of dried leaves on the growth of recipient lettuce seedlings was examined by the sandwich method. The allelopathic activity on protoplast growth was examined by co-culture with recipient lettuce leaf protoplasts in 50 µl liquid medium using a 96-well culture plate. Non-spherically enlarged or dividing protoplasts of lettuce were counted under an inverted microscope. Inhibition of yellow accumulation during lettuce protoplast growth was quantitated by image analysis of scanned digital images of 96-well culture plates. The results were described as the percentages of control without A. thaliana. The results were compared with those obtained using several plants which had strong allelopathic activities on recipient lettuce using the same methods. The growth of lettuce protoplasts was inhibited at both 4 and 8 days of culture with protoplasts of A. thaliana. The results suggested the usefulness of the protoplast co-culture method for future studies on allelopathy.

Preparation of protoplasts of the fungus Trametes hirsuta 072 and study of the effect of antioxidants on their formation and regeneration

The consistent application of homogenization and enzymatic treatment is required to obtain protoplasts from the basidiomycete fungus Trametes hirsuta. The maximum yield of protoplasts (∼2.5 × 107/mL) was achieved when mycelium in the exponential growth phase (60 h) was used. The maximum stability was observed in MES+ buffer during 4 h of incubation; in this case the titer reduction was 5–7%. Studies of the effect of antioxidants with different antioxidant capacities expressed in mmol equivalents of Trolox (ascorbate, 0.99; α-tocopherol, 1.0; β-carotene, 2.14; quercetin, 3.98) indicated that the yield of protoplasts was increased in the presence of β-carotene and quercetin by 18–24%. The studied antioxidants did not affect the protoplasts stability. The degree of regeneration of protoplasts correlated with the antioxidant capacity of the studied antioxidants and was maximal (0.4%) in the presence of β-carotene and quercetin; it was 0.1% in the presence of MES+. The rate of protoplast growth was two times higher in the presence of β-carotene and quercetin.

Effect of polyvinylpyrrolidone and activated charcoal on formation of microcallus from grapevine protoplasts ( Vitis sp.)

The effect of the addition of polyvinylpyrrolidone (PVP-40) to grapevine protoplast cultures ( Vitis sp. cv. Vidal blanc) at different stages of development (day 0, 7 and 14 of cultivation) and the influence of activated charcoal (AC) in several concentrations (0, 0.1, 0.5 and 1.0 %) on protoplast growth were studied. Both additives were investigated using different modified culture media (CPW-13, V/KM, MS-P). The application of 0.5% PVP could not prevent browning of the culture media but reduced it to a low level. Although the effect of PVP on plating efficiency was not clear, the formation of microcalli from grapevine protoplasts was remarkably improved when adding PVP at ''day 0'' or ''day 7'' of cultivation. AC could prevent browning of the media in all concentrations tested but at the same time inhibited plating efficiency. Conversely, formation of microalli occurred only with 0.5 and 1.0% AC, but at very low frequencies. A superior suitability of one of the culture media tested for grapevine protoplasts culture could not been found.

Allelopathy in a Leguminous Mangrove Plant, Derris indica: Protoplast Co-culture Bioassay and Rotenone Effect

To investigate allelopathic activity of a leguminous mangrove plant, Derris indica, the 'Protoplasts Co-culture Method' for bioassay of allelopathy was developed using suspension culture. A suspension culture was induced from immature seed and sub-cultured in Murashige and Skoog's (MS) basal medium containing 10 μM each of 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzyladenine (BA). The protoplasts were isolated using the separate wells method with 2% each of Cellulase RS, Driselase 20 and Macerozyme R10 in 0.4 M mannitol solution. Protoplast cultures of D. indica revealed that high concentrations of cytokinins, BA and thidiazuron, were effective for cell divisions. The co-cultures of D. indica protoplasts with recipient lettuce protoplasts using 96 multi-well culture plates were performed in MS basal medium containing 0.4 M mannitol solution and 1 μM 2,4-D and 0.1 μM BA. The protoplast density of D. indica used in co-culturing varied from 6 x 10(3) - 10(5) / mL. Very strong inhibitory allelopathic effects of D. indica protoplasts on lettuce protoplast growth were found. A similar strong inhibitory allelopathic activity of dried young leaves on lettuce seedling growth was also observed by using the sandwich method. Rotenone, which is a component of Derris root, dissolved in DMSO, was highly inhibitory on the growth of lettuce protoplasts in culture and this could be one of the causes of the strong allelopathic activity of D. indica.

Protoplast Co-culture Bioassay for Allelopathy in Leguminous Plants, Leucaena leucocephala and Mucuna gigantea, Containing Allelochemical Amino Acids, Mimosine and L-DOPA

Protoplasts isolated from calluses of two woody leguminous plants, Leucaena leucocephala and Mucuna gigantea, which contain high levels of the allelochemical amino acids, mimosine and l-DOPA, respectively, were co-cultured to examine their allelopathic activities. The young leaves were first confirmed to have strong inhibitory activity by the sandwich method. Callus cultures were induced and sub-cultured from seeds of L. leucocephala and from leaves of M. gigantea in Murashige and Skoog’s (MS) basal media containing high concentrations of auxin and cytokinins. Protoplasts of both calluses were isolated using the separate well method under strong enzymatic conditions, in high osmotic, 0.8 M mannitol solution. Protoplasts of both species had strong inhibitory effects on the recipient protoplasts of cotyledons of Lactuca sativa (lettuce) co-cultured using 96 multi-well culture plates in the MS basal medium, containing 1 ?M 2,4-dichlorophenoxyacetic acid, 0.1 ?M benzyladenine and 0.8 M mannitol solution. Mimosine was less inhibitory than l-DOPA on the growth of lettuce protoplasts at the stage of colony formation. Amino acid profiles of calluses and protoplasts of the above two species and Mucuna pruriens showed very low contents of mimosine and l-DOPA, respectively. The cause of the high inhibitory allelopathic activities found in Leucaena and Mucuna protoplasts on the growth of lettuce protoplasts was discussed.