Rose protoplast isolation and culture and heterokaryon selection by immobilization in extra thin alginate film

Optimizing Brassica oleracea L. Breeding Through Somatic Hybridization Using Cytoplasmic Male Sterility (CMS) Lines: From Protoplast Isolation to Plantlet Regeneration

The Brassica oleracea L. species embrace important horticultural crops, such as broccoli, cauliflower, and cabbage, which are highly valued for their beneficial nutritional effects. However, the complexity of flower emasculation in these species has forced breeders to adopt biotechnological approaches such as somatic hybridization to ease hybrid seed production. Protoplasts entail a versatile tool in plant biotechnology, supporting breeding strategies that involve genome editing and hybridization. This review discusses the use of somatic hybridization in B. oleracea L. as a biotechnological method for developing fusion products with desirable agronomic traits, particularly cytoplasmic male sterile (CMS) condition. These CMS lines are critical for implementing a cost-effective, efficient, and reliable system for producing F1 hybrids. We present recent studies on CMS systems in B. oleracea L. crops, providing an overview of established models that explain the mechanisms of CMS and fertility restoration. Additionally, we emphasize key insights gained from protoplast fusion applied to B. oleracea L. breeding. Key steps including pre-treatments of donor plants, the main tissues used as sources of parental protoplasts, methods for obtaining somatic hybrids and cybrids, and the importance of establishing a reliable plant regeneration method are discussed. Finally, the review explores the incorporation of genome editing technologies, such as CRISPR-Cas9, to introduce multiple agronomic traits in Brassica species. This combination of advanced biotechnological tools holds significant promise for enhancing B. oleracea breeding programs in the actual climate change context.

Early selection of carrot somatic hybrids: a promising tool for species with high regenerative ability

BACKGROUND

Since its discovery, somatic hybridization has been used to overcome the sexual barriers between cultivated and wild species. A combination of two somatic cells might provide a novel set of features, often of agronomical importance. Here, we report a successful approach for production and selection of interspecific somatic hybrid plants between cultivated and wild carrot using dual-labelling of protoplasts and an early selection of fused cells via micromanipulator. Both subspecies used in this study are characterised by a very high regenerative ability in protoplast cultures. Thus, a precise and effective method of hybrid selection is essential to assure the development and regeneration of much less numerous heterokaryons in the post-fusion cell mixture.

RESULTS

Electrofusion parameters, such as alternating current and direct current, were optimised for an efficient alignment of protoplasts and reversible membrane breakdown followed by a cell fusion. Four hundred twenty-nine cells emitting green-red fluorescence, identified as hybrids, were obtained. Co-culture with donor-derived protoplasts in the alginate feeder layer system stimulated re-synthesis of the cell wall and promoted cell divisions of fusants. Somatic embryogenesis occurred in hybrid-derived microcalli cultures, followed by plant regeneration. Regenerated hybrids produced yellowish storage roots and leaves of an intermediate shape between cultivated and wild subspecies. The intron length polymorphism analysis revealed that 123 of 124 regenerated plants were hybrids.

CONCLUSIONS

The developed protocol for protoplast fusion and an early selection of hybrids may serve as an alternative to combining genomes and transferring nuclear or cytoplasmatic traits from wild Daucus species to cultivated carrot.

An efficient method for protoplast-mediated production of transformed castor bean (Ricinus communis) lines

OBJECTIVE

The purpose of this study was to develop a method for the isolation, culture, and PEG-mediated protoplast transfection from leaves of in vitro-grown plants of Ricinus communis.

RESULTS

Factors such as the enzymatic composition and the incubation time were evaluated. The enzymatic solution, containing 1.6% Cellulase-R10 and 0.8% Macerozyme-R10, with 16 h of incubation, was the best condition to achieve a high protoplast yield (481.16 × 10⁴ protoplasts/g FW) with a high percentage of viability (95%). The combination and concentration of enzymes have been shown to affect the protoplast isolation efficiency significantly. Furthermore, we found that a higher number of protoplasts (8.5 × 10⁵ protoplast/g FW) was obtained at a longer incubation time, but their viability decreased. We obtained a simple and efficient protocol to isolate protoplast from Ricinus communis leaves and culture. A PEG-mediated protoplast transfection protocol was also established to introduce plasmid DNA into Ricinus communis genotypes cultivated in Colombia. Thus, strengthening advances in the genetic improvement processes for this crop are presented.

Tissue Culture in Ornamentals: Cultivation Factors, Propagation Techniques, and Its Application

Ornamentals come in a variety of shapes, sizes, and colors to suit a wide range of climates, landscapes, and gardening needs. Compared to demand, a shortage of plant materials and diversity force the search for solutions for their constant acquisition and improvement to increase their commercial value, respectively. In vitro cultures are a suitable solution to meet expectations using callus culture, somatic embryogenesis, protoplast culture, and the organogenesis of protocorm-like bodies; many of these techniques are commercially practiced. Factors such as culture media, explants, carbohydrates, plant growth regulators, and light are associated with the success of in vitro propagation. Techniques, especially embryo rescue and somatic hybridization, are widely used to improve ornamentals. The development of synthetic seed allows season-independent seed production and preservation in the long term. Despite the advantages of propagation and the improvement of ornamentals, many barriers still need to be resolved. In contrast to propagation and crop developmental studies, there is also a high scope for molecular studies, especially epigenetic changes caused by plant tissue culture of ornamentals. In this review, we have accumulated and discussed an overall update on cultivation factors, propagation techniques in ornamental plant tissue culture, in vitro plant improvement techniques, and future perspectives.

Real-time detection of somatic hybrid cells during electrofusion of carrot protoplasts with stably labelled mitochondria

Somatic hybridisation in the carrot, as in other plant species, enables the development of novel plants with unique characteristics. This process can be induced by the application of electric current to isolated protoplasts, but such electrofusion requires an effective hybrid cell identification method. This paper describes the non-toxic fluorescent protein (FP) tagging of protoplasts which allows discrimination of fusion components and identification of hybrids in real-time during electrofusion. One of four FPs: cyan (eCFP), green (sGFP), yellow (eYFP) or the mCherry variant of red FP (RFP), with a fused mitochondrial targeting sequence, was introduced to carrot cell lines of three varieties using Agrobacterium-mediated transformation. After selection, a set of carrot callus lines with either GFP, YFP or RFP-labelled mitochondria that showed stable fluorescence served as protoplast sources. Various combinations of direct current (DC) parameters on protoplast integrity and their ability to form hybrid cells were assessed during electrofusion. The protoplast response and hybrid cell formation depended on DC voltage and pulse time, and varied among protoplast sources. Heterofusants (GFP + RFP or YFP + RFP) were identified by detection of a dual-colour fluorescence. This approach enabled, for the first time, a comprehensive assessment of the carrot protoplast response to the applied electric field conditions as well as identification of the DC parameters suitable for hybrid formation, and an estimation of the electrofusion success rate by performing real-time observations of protoplast fluorescence.

Dendrobium protoplast co-culture promotes phytochemical assemblage in vitro

The present study is intended to analyze the occurrence of potent, low produce, naturally occurring stilbenes in protoplasts of wild species and hybrids of Dendrobium. The wild species selected for the study was Dendrobium ovatum, endemic to Western Ghats of India. Protoplasts were isolated from leaves and tepal tissues of all the species and were cultured purely to generate homofusants and cross-cultured to raise heterofusants. Phytochemical composition of protoplast culture with atypical and pure microcolonies was performed using mass spectrometry. Enzyme cocktail of 4% pectinase together with 2% cellulase displayed the highest competence for protoplast isolations. Maximum protoplast density of 30.11 × 10⁴/ml was obtained from D. ovatum leaves in 2 h. Subcellular features such as the presence of partially formed cell wall, the position of the nucleus, chloroplast density, colony existence, and integrity of the plasma membrane were analyzed. Among the pure and cross-cultured protoplasts, the number of heterofusants and homofusants formed were enumerated. The spectral feature extraction of the mass spectrometry indicated the presence of five phenolic marker compounds, viz., tristin, confusarin, gigantol, moscatilin, and resveratrol, some of them in pure and others in assorted protoplast cultures raised from Dendrobium leaves and tepals. The study demonstrated that protoplast fusion technique enabled phytochemical assemblage in vitro as stilbenes tend to get restricted either in a tissue or species specific manner. This is the first report showing the presence of resveratrol, moscatilin, tristin, gigantol, and confusarin in wild and hybrid species from cultured Dendrobium protoplasts in vitro.

A simple and effective method to encapsulate tobacco mesophyll protoplasts to maintain cell viability

Protoplasts have been widely used for genetic transformation, cell fusion, and somatic mutation due to the absence of a cell wall. However, without the protection of a cell wall, protoplasts are easy to rupture and aggregate during washing, collecting, and gene transfection. In this work, we propose a simple and effective silica/alginate two-step method to immobilize protoplasts with advantages in experimental manipulation and microscopic imaging, as well as in potentially studying cell biological processes such as secretion and metabolism. The proposed two-step immobilization method adopts Transwell with clear tissue culture-treated membrane to support protoplasts in the form of uniform thin layer, which has three unique properties.

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The tissue culture-treated membrane has a good affinity for the plant cell; thus, protoplasts can spread evenly and form a very thin layer.

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There are more choices for membrane pore size, depending on the application.

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It is very convenient to change or collect the solution without mechanically disturbing the protoplasts. This simple and effective silica sol–gel/alginate two-step immobilization of protoplasts in Transwell has great potential for applications in genetic transformation, metabolite production, and migration assays.

Progress in plant protoplast research

In this review we focus on recent progress in protoplast regeneration, symmetric and asymmetric hybridization and novel technology developments. Regeneration of new species and improved culture techniques opened new horizons for practical breeding in a number of crops. The importance of protoplast sources and embedding systems is discussed. The study of reactive oxygen species effects and DNA (de)condensation, along with thorough phytohormone monitoring, are in our opinion the most promising research topics in the further strive for rationalization of protoplast regeneration. Following, fusion and fragmentation progress is summarized. Genomic, transcriptomic and proteomic studies have led to better insights in fundamental processes such as cell wall formation, cell development and chromosome rearrangements in fusion products, whether or not obtained after irradiation. Advanced molecular screening methods of both genome and cytoplasmome facilitate efficient screening of both symmetric and asymmetric fusion products. We expect that emerging technologies as GISH, high resolution melting and next generation sequencing will pay major contributions to our insights of genome creation and stabilization, mainly after asymmetric hybridization. Finally, we demonstrate agricultural valorization of somatic hybridization through enumerating recent introgression of diverse traits in a number of commercial crops.