Agrobacterium-delivered virulence protein VirE2 is trafficked inside host cells via a myosin XI-K–powered ER/actin network
Thursday, 2017/03/16 | 07:58:19
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Qinghua Yang, Xiaoyang Li, Haitao Tu, and Shen Q. Pan SignificanceAgrobacterium 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. AbstractAgrobacterium 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.
See: http://www.isaaa.org/kc/cropbiotechupdate/newsletter/default.asp?Date=3/8/2017 PNAS March 14 2017; vol.114; no.11: 2982–2987
Fig. 1. Agrobacterium-delivered VirE2 trafficking on a cellular structure and entering the nucleus. A. tumefaciens EHA105virE2::GFP11 cells were infiltrated into transgenic tobacco (Nb308A) leaves expressing GFP1-10 and DsRed. The leaf epidermal cells were observed at 2 d after agroinfiltration by confocal microscopy using an Olympus UPLSAPO 60× N.A. 1.20 water-immersion objective. Red indicates free DsRed; green indicates VirE2-GFPcomp. (A) Time-lapse images of VirE2 aggregates trafficking along a linear cellular structure and entering the nucleus. Relative time is shown at top left. (Scale bar: 20 μm.) (B) Effects of chemical treatments on VirE2 trafficking. Chemicals were infiltrated into leaf samples 6 h before observation. Control: 0.5% DMSO (Colc, 500 μM; CytoD, 20 μM; BFA, 100 μg/mL). (Scale bar: 20 μm.) (C) Mean velocities of VirE2 aggregate movement after chemical treatments. Data were analyzed with ANOVA and Tukey test (P < 0.05). (D) Plot of the movements of 20 individual VirE2 aggregates relative to a common origin for each treatment. |
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