Technological Development and Application of Plant Genetic Transformation

Abstract

Genetic transformation is an important strategy for enhancing plant biomass or resistance in response to adverse environments and population growth by imparting desirable genetic characteristics. Research on plant genetic transformation technology can promote the functional analysis of plant genes, the utilization of excellent traits, and precise breeding. Various technologies of genetic transformation have been continuously discovered and developed for convenient manipulation and high efficiency, mainly involving the delivery of exogenous genes and regeneration of transformed plants. Here, currently developed genetic transformation technologies were expounded and compared. Agrobacterium-mediated gene delivery methods are commonly used as direct genetic transformation, as well as external force-mediated ways such as particle bombardment, electroporation, silicon carbide whiskers, and pollen tubes as indirect ones. The regeneration of transformed plants usually involves the de novo organogenesis or somatic embryogenesis pathway of the explants. Ectopic expression of morphogenetic transcription factors (Bbm, Wus2, and GRF-GIF) can significantly improve plant regeneration efficiency and enable the transformation of some hard-to-transform plant genotypes. Meanwhile, some limitations in these gene transfer methods were compared including genotype dependence, low transformation efficiency, and plant tissue damage, and recently developed flexible approaches for plant genotype transformation are discussed regarding how gene delivery and regeneration strategies can be optimized to overcome species and genotype dependence. This review summarizes the principles of various techniques for plant genetic transformation and discusses their application scope and limiting factors, which can provide a reference for plant transgenic breeding.

Keywords: Agrobacterium; nanoparticles; particle bombardment; plant genetic transformation.

Figure 1

Schematic diagram of T-DNA transfer and integration into the plant genome. VirA, VirG: perception of phenolic compounds from plant wounds/induction of virulence (Vir) gene expression. VirD1: DNA topoisomerase processing T-DNA. VirD2: Endonuclease cutting the T-DNA border to initiate T-strand synthesis and attached to 5′ of T-strand/formation of T-DNA complex/transport of the T-DNA complex through nuclear pores. VirE1: Plays the role of a chaperone to stabilize VirE2 in Agrobacterium. VirE2: Single-strand DNA binding protein protecting the T-strand from nuclease. T4SS: Type IV secretion system.

Figure 2

Schematic diagram of different genetic transformation mediated by the direct method. (a) Particle-bombardment-mediated plant transformation. (b) Electroporation-mediated transformation. (c) Liposome-mediated transformation. (d) Silicon-carbide-whisker-mediated transformation. (e) Microinjection-mediated transformation. (f) Pollen-tube-pathway-mediated transformation.

Figure 3

Nanoparticle-mediated gene transfer: (a) magnetic-nanoparticle-mediated gene transfer; (b) peptide-nanoparticle-mediated gene transfer; (c) layered-double-hydroxide-nano-transporter-mediated gene transfer; 1. plant cell walls pathway; 2. plasma membrane by a non-intracellular pathway; 3. endocytosis pathway; (d) DNA-nanostructure-mediated gene transfer; (e) carbon-nanotube-mediated gene transfer.