Agrobacterium-mediated plant transformation (AMT) is a cornerstone of modern plant biotechnology. However, many plant species/varieties are recalcitrant to Agrobacterium infection due to elicited plant defense responses. This study engineered Agrobacterium tumefaciens to express a type III secretion system (T3SS) from Pseudomonas syringae, delivering effectors AvrPto, AvrPtoB, or HopAO1 to suppress host defenses. This resulted in a ~250–400% increase in AMT of wheat, alfalfa, and switchgrass. The engineered A. tumefaciens also successfully delivered the plant protein histone H2A-1, further enhancing AMT. This approach has significant implications for basic research and agricultural biotechnology, enabling transformation of recalcitrant species and non-transgenic protein delivery into plant cells.

Vidhyavathi Raman, Clemencia M. Rojas, Balaji Vasudevan, Kevin Dunning, Jaydeep Kolape, Sunhee Oh, Jianfei Yun, Lishan Yang, Guangming Li, Bikram D. Pant, Qingzhen Jiang, Kirankumar S. Mysore