Cell-penetrating peptides (CPPs) are nanocarriers with property to translocate across cell membranes and target specifically subcellular localisations. CPPs also have the capacity to non-covalently bind to cargo molecules, such as nucleic acid and protein, and transport them specifically to subcellular destinations. The nuclear targeting cargo-CPP uptake pattern between the mammalian system and the plant system is very similar. The dimer of Tat 49-57 RKKRRQRRR basic domain has been extensively used for wheat and triticale nuclear targeting and delivery of dsDNA, ssDNA and proteins. Synthetic or in vivo produced nucleic acid, proteins and CPPs are blocks that conjugate to form nanocomplexes in a relatively predictable manner. ssDNA binding proteins such as RecA, Rad51 and VirD2 were used to form with ssDNA various cargo complexes, and increased the integrity of ssDNA in the haploid plant genome of microspore. Two novel classes of CPPs were recently discovered with property to carry dsDNA specifically into the chloroplast or ethioplast, and mitochondria of protoplasts and microspore.
The distinct ability of CPPs to deliver functional macromolecules cargoes specifically in one of the three organelles that are otherwise restricted to cross the membrane has lead to development of novel nanocarrier-mediated gene and protein delivery methods in somatic cells and microspores. CPPs offer an alternative to Agrobacterium and biolistic mediated transformation for the production of transgenic plants. CPP mediated transfection in plant microspore opened new possibilities for precision genetic engineering of the three organelles of this unique cell type and crops of commercial importance.