Shanjin Huang’s group published an eLife article revealing the mechanism of actin-mediated regulation of plasmodesmata permeability

2018-09-04 23:12:32

On August 16th, 2018, a research team led by Dr. Shanjin Huang from School of Life Sciences, Tsinghua University published a research article entitled “Arabidopsis Formin 2 Regulates Cell-to-Cell Trafficking by Capping and Stabilizing Actin Filaments at Plasmodesmata” in eLife. In this study, the authors demonstrated that AtFH2, along with several Class I formins, localizes to PD and is involved in the regulation of cell-to-cell trafficking by regulating actin dynamics at PD.

Plasmodesmata (PD) function as the intercellular channels in plants, and are important for the growth and development of plants, as well as during their interaction with the surrounding environment. The permeability of PD must be precisely regulated. However, the mechanisms that tightly regulate the permeability of PD are mostly unknown. The actin cytoskeleton has been implicated in intercellular communication via PD, whereas the underlying mechanism is still not completely understood. Studies in this area have progressed slowly for at least two reasons. First, researchers still lack approaches to specifically visualize actin at PD since they are small and buried deeply in the cell wall. Consequently, the existence of filamentous forms of actin at PD remains controversial. Second, researchers still lack approaches to specifically perturb actin dynamics at PD. Identification of the native components of the actin cytoskeletal system that specifically localize to PD may provide targets for the genetic manipulation of the actin cytoskeleton in this region, which will enhance our understanding of how actin at PD regulates cell-to-cell trafficking. 

This study found that AtFH2, a member of the Arabidopsis thaliana formin family, specifically localizes to PD via its N-terminal transmembrane domain. Loss of function of AtFH2 increases the permeability of intercellular trafficking in Arabidopsis. In vitro biochemical characterization showed that AtFH2 lacks the characteristic actin nucleation activity but retains the actin filament barbed end capping activity that stabilizes actin filaments in vitro. Further studies revealed that the interaction between AtFH2 and actin filaments is crucial for its function in regulating the permeability of PD. Based on these data, the authors proposed that AtFH2 specifically localizes to the membrane of PD via its N-terminal transmembrane domain that anchors and stabilizes actin filaments to PD via capping the barbed end of actin filaments. This study suggests that the stability and/or the amount of actin filaments at PD is crucial for the permeability of PD. The study also found that some rice formins localize to PD, suggesting that the mechanism of the involvement of formins in the regulation of PD permeability is conserved in plants.

Dr. Min Diao from Shanjin Huang’s group is the first author and Dr. Shanjin Huang is the corresponding author of this article. This work was collaborated with Prof. Yule Liu’s group at the School of Life Sciences, Tsinghua University. This work was funded by National Natural Science Foundation of China and Tsinghua University.

Research article link: https://elifesciences.org/articles/36316

Fig. 1. AtFH2 Localizes to PD

Fig. 2. The Interaction between AtFH2 and Actin Filaments is Crucial for Its Role in Regulating Intercellular Trafficking