Perspectives on new opportunities for nano-enabled strategies for gene delivery to plants using nanoporous materials.

MAIN CONCLUSION: Engineered nanocarriers have great potential to deliver different genetic cargos to plant cells and increase the efficiency of plant genetic engineering. Genetic engineering has improved the quality and quantity of crops by introducing desired DNA sequences into the plant genome. Traditional transformation strategies face constraints such as low transformation efficiency, damage to plant tissues, and genotype dependency. Smart nanovehicle-based delivery is a newly emerged method for direct DNA delivery to plant genomes. The basis of this new approach of plant genetic transformation, nanomaterial-mediated gene delivery, is the appropriate protection of transferred DNA from the nucleases present in the cell cytoplasm through the nanocarriers. The conjugation of desired nucleic acids with engineered nanocarriers can solve the problem of genetic manipulation in some valuable recalcitrant plant genotypes. Combining nano-enabled genetic transformation with the new and powerful technique of targeted genome editing, CRISPR (clustered regularly interspaced short palindromic repeats), can create new protocols for efficient improvement of desired plants. Silica-based nanoporous materials, especially mesoporous silica nanoparticles (MSNs), are currently regarded as exciting nanoscale platforms for genetic engineering as they possess several useful properties including ordered and porous structure, biocompatibility, biodegradability, and surface chemistry. These specific features have made MSNs promising candidates for the design of smart, controlled, and targeted delivery systems in agricultural sciences. In the present review, we discuss the usability, challenges, and opportunities for possible application of nano-enabled biomolecule transformation as part of innovative approaches for target delivery of genes of interest into plants.

Current status and biotechnological advances in genetic engineering of ornamental plants.

Cut flower markets are developing in many countries as the international demand for cut flowers is rapidly growing. Developing new varieties with modified characteristics is an important aim in floriculture. Production of transgenic ornamental plants can shorten the time required in the conventional breeding of a cultivar. Biotechnology tools in combination with conventional breeding methods have been used by cut flower breeders to change flower color, plant architecture, post-harvest traits, and disease resistance. In this review, we describe advances in genetic engineering that have led to the development of new cut flower varieties.

Methods for genetic transformation in Dendrobium.

KEY MESSAGE: The genetic transformation of Dendrobium orchids will allow for the introduction of novel colours, altered architecture and valuable traits such as abiotic and biotic stress tolerance. The orchid genus Dendrobium contains species that have both ornamental value and medicinal importance. There is thus interest in producing cultivars that have increased resistance to pests, novel horticultural characteristics such as novel flower colours, improved productivity, longer flower spikes, or longer post-harvest shelf-life. Tissue culture is used to establish clonal plants while in vitro flowering allows for the production of flowers or floral parts within a sterile environment, expanding the selection of explants that can be used for tissue culture or genetic transformation. The latter is potentially the most effective, rapid and practical way to introduce new agronomic traits into Dendrobium. Most (69.4 %) Dendrobium genetic transformation studies have used particle bombardment (biolistics) while 64 % have employed some form of Agrobacterium-mediated transformation. A singe study has explored ovary injection, but no studies exist on floral dip transformation. While most of these studies have involved the use of selector or reporter genes, there are now a handful of studies that have introduced genes for horticulturally important traits.

Enhancement of phosphate absorption by garden plants by genetic engineering: a new tool for phytoremediation.

Although phosphorus is an essential factor for proper plant growth in natural environments, an excess of phosphate in water sources causes serious pollution. In this paper we describe transgenic plants which hyperaccumulate inorganic phosphate (Pi) and which may be used to reduce environmental water pollution by phytoremediation. AtPHR1, a transcription factor for a key regulator of the Pi starvation response in Arabidopsis thaliana, was overexpressed in the ornamental garden plants Torenia, Petunia, and Verbena. The transgenic plants showed hyperaccumulation of Pi in leaves and accelerated Pi absorption rates from hydroponic solutions. Large-scale hydroponic experiments indicated that the enhanced ability to absorb Pi in transgenic torenia (AtPHR1) was comparable to water hyacinth a plant that though is used for phytoremediation causes overgrowth problems.

Expression of flavonoid 3',5'-hydroxylase and acetolactate synthase genes in transgenic carnation: assessing the safety of a nonfood plant.

For 16 years, genetically modified flowers of carnation ( Dianthus caryophyllus ) have been sold to the floristry industry. The transgenic carnation carries a herbicide tolerance gene (a mutant gene encoding acetolactate synthase (ALS)) and has been modified to produce delphinidin-based anthocyanins in flowers, which conventionally bred carnation cannot produce. The modified flower color has been achieved by introduction of a gene encoding flavonoid 3',5'-hydroxylase (F3'5'H). Transgenic carnation flowers are produced in South America and are primarily distributed to North America, Europe, and Japan. Although a nonfood crop, the release of the genetically modified carnation varieties required an environmental risk impact assessment and an assessment of the potential for any increased risk of harm to human or animal health compared to conventionally bred carnation. The results of the health safety assessment and the experimental studies that accompanied them are described in this review. The conclusion from the assessments has been that the release of genetically modified carnation varieties which express F3'5'H and ALS genes and which accumulate delphinidin-based anthocyanins do not pose an increased risk of harm to human or animal health.

Genetic modification; the development of transgenic ornamental plant varieties.

Plant transformation technology (hereafter abbreviated to GM, or genetic modification) has been used to develop many varieties of crop plants, but only a few varieties of ornamental plants. This disparity in the rate and extent of commercialisation, which has been noted for more than a decade, is not because there are no useful traits that can be engineered into ornamentals, is not due to market potential and is not due to a lack of research and development activity. The GM ornamental varieties which have been released commercially have been accepted in the marketplace. In this article, progress in the development of transgenic ornamentals is reviewed and traits useful to both consumers and producers are identified. In considering possible factors limiting the release of genetically modified ornamental products it is concluded that the most significant barrier to market is the difficulty of managing, and the high cost of obtaining, regulatory approval.

Genetic modification in floriculture.

Micro-propagation, embryo rescue, mutagenesis via chemical or irradiation means and in vitro inter-specific hybridisation methods have been used by breeders in the floriculture industry for many years. In the past 20 years these enabling technologies have been supplemented by genetic modification methods. Though many genes of potential utility to the floricultural industry have been identified, and much has been learnt of the genetic factors and molecular mechanisms underlying phenotypes of great importance to the industry, there are only flower colour modified varieties of carnation and rose in the marketplace. To a large extent this is due to unique financial barriers to market entry for genetically modified varieties of flower crops, including use of technology fees and costs of regulatory approval.