In planta particle bombardment (iPB): A new method for plant transformation and genome editing

Transformation is a key step in modern breeding technology that involves genome editing. The requirement for in vitro tissue culture and regeneration hampers application of this technology to commercially important varieties of many crop species. To overcome this problem, we developed a simple and reproducible in planta transformation method in wheat (Tritticum aestivum L.). Our in planta particle bombardment (iPB) method utilizes the shoot apical meristem (SAM) as a target tissue. The SAM contains a subepidermal cell layer termed L2, from which germ cells later develop during floral organogenesis. The iPB method can also be used for genome editing through transient CRISPR/Cas9 expression or direct delivery of the CRISPR/Cas9 ribonucleoprotein. In this review, we describe the iPB technology and provide an overview of its current and future applications in plant transformation and genome editing.