Qinghua Yang, Xiaoyang Li, Haitao Tu, and Shen Q. Pan
Agrobacterium causes diseases in a wide range of host plants. It has been developed as a genetic tool to transform a variety of plant species and nonplant organisms. It can achieve a transformation efficiency as high as 100%. However, it is not clear how Agrobacterium virulence factors are trafficked through host cytoplasm to achieve such a wide host range and a high efficiency. Here we report that Agrobacterium-delivered VirE2 is trafficked inside plant cells via the endoplasmic reticulum and F-actin network. This trafficking is powered by myosin XI-K. As the myosin-powered actin network is well conserved, our data suggest that Agrobacterium hijacks the conserved host network for virulence trafficking to transform a wide range of recipient cells with high efficiency.
Agrobacterium tumefaciens causes crown gall tumors on various plants by delivering transferred DNA (T-DNA) and virulence proteins into host plant cells. Under laboratory conditions, the bacterium is widely used as a vector to genetically modify a wide range of organisms, including plants, yeasts, fungi, and algae. Various studies suggest that T-DNA is protected inside host cells by VirE2, one of the virulence proteins. However, it is not clear how Agrobacterium-delivered factors are trafficked through the cytoplasm. In this study, we monitored the movement of Agrobacterium-delivered VirE2 inside plant cells by using a split-GFP approach in real time. Agrobacterium-delivered VirE2 trafficked via the endoplasmic reticulum (ER) and F-actin network inside plant cells. During this process, VirE2 was aggregated as filamentous structures and was present on the cytosolic side of the ER. VirE2 movement was powered by myosin XI-K. Thus, exogenously produced and delivered VirE2 protein can use the endogenous host ER/actin network for movement inside host cells. The A. tumefaciens pathogen hijacks the conserved host infrastructure for virulence trafficking. Well-conserved infrastructure may be useful for Agrobacterium to target a wide range of recipient cells and achieve a high efficiency of transformation.
PNAS March 14 2017; vol.114; no.11: 2982–2987