Nanocarriers for Transgene Expression in Pollen as a Plant Biotechnology Tool

As the male gametophyte of flowering plants, pollen grains are ideal targets for the introduction of transgenes for plant genetic engineering and crop improvement. However, the difficulty of delivering exogenous DNA into pollen grains, because of chemically inert cell walls, has hindered their widespread application in plant biotechnology. Herein, we report a new class of nanocarriers, composed of imidazolium (IM)-functionalized single-walled carbon nanotubes (SWNTs), which can efficiently traverse past pollen barriers and deliver genes without external physical aid. IM-SWNTs display high biocompatibility with pollen grains, compared to existing SWNT nanocarriers previously used for cargo delivery into living plant cells. Using IM-SWNTs as nanotransporters, we investigate the compatibility of various pollen-specific promoters with oil palm pollen transcription machinery. We show that nanoparticle transport past the pollen plasma membrane is mainly controlled by its zeta potential, and we describe this entry mechanism with the lipid exchange envelope penetration model. We further estimate the pollen membrane effective dielectric constant with this model. These findings provide insights for the rational design and refinement of nanocarriers for plant biotechnology applications.