Functional protein delivery to plants can facilitate the design of desired functions by modulation of biological processes and plant traits without the risk of random gene mutation. Current protein deployment technologies are limited by narrow host range, tissue damage, and poor scalability. Physical barriers in plants, including cell walls and plasma membranes limit protein delivery to desired plant tissues. To tackle these challenges, a cationic high aspect ratio polymeric nanocarriers (PNCs) platform is developed to enable efficient protein delivery to plants. The ability to precisely design PNCs’ size and aspect ratio allowed us to find a cutoff of ≈14 nm in the cell wall, below which cationic PNCs can autonomously overcome the barrier and carry their cargo into plant cells. To exploit these findings, a reduction-oxidation sensitive green fluorescent protein (roGFP) is deployed as a stress sensor protein cargo in a model plant Nicotiana benthamiana and common crop plants, including tomato and maize. In vivo imaging of PNC-roGFP enabled optical monitoring of plant response to wounding, biotic, and heat stressors. These results show that PNCs can be precisely designed below the size exclusion limit of cell walls and membranes to overcome current limitations in protein delivery to plants and facilitate species-independent plant engineering to improve plants' resilience to climate change.
