The Rubisco Small Subunit Is Involved in Tobamovirus Movement and Tm-22-Mediated Extreme Resistance

Jinping Zhao,Yule Liu,Yiguo Hong,Qi Liu,Qi Jia,Haili Zhang

doi:10.1104/pp.112.209213

Abstract

The multifunctional movement protein (MP) of Tomato mosaic tobamovirus (ToMV) is involved in viral cell-to-cell movement, symptom development, and resistance gene recognition. However, it remains to be elucidated how ToMV MP plays such diverse roles in plants. Here, we show that ToMV MP interacts with the Rubisco small subunit (RbCS) of Nicotiana benthamiana in vitro and in vivo. In susceptible N. benthamiana plants, silencing of NbRbCS enabled ToMV to induce necrosis in inoculated leaves, thus enhancing virus local infectivity. However, the development of systemic viral symptoms was delayed. In transgenic N. benthamiana plants harboring Tobacco mosaic virus resistance-2² (Tm-2²), which mediates extreme resistance to ToMV, silencing of NbRbCS compromised Tm-2²-dependent resistance. ToMV was able to establish efficient local infection but was not able to move systemically. These findings suggest that NbRbCS plays a vital role in tobamovirus movement and plant antiviral defenses.

Highlights

The multifunctional movement protein (MP) of Tomato mosaic tobamovirus (ToMV) is involved in viral cell-to-cell movement, symptom development, and resistance gene recognition
Through a range of in vitro and in vivo proteinprotein interaction assays, we have identified Nicotiana benthamiana RbCS (NbRbCS) as a new ToMV MP-interacting host protein
NbRbCS interacted with the N-terminal and middle domains of ToMV MP. These domains are conserved among tobamovirus MPs, suggesting that Rubisco small subunit (RbCS) may commonly interact with MPs from tobamoviruses

Summary

Introduction

The multifunctional movement protein (MP) of Tomato mosaic tobamovirus (ToMV) is involved in viral cell-to-cell movement, symptom development, and resistance gene recognition It remains to be elucidated how ToMV MP plays such diverse roles in plants. These TMV MPbinding host factors include cell wall-associated proteins such as pectin methylesterase (Chen et al, 2000), calreticulin (Meshi et al, 1989), ANK1 (Ueki et al, 2010), and the cellular DnaJ-like protein MPIP1 (Shimizu et al, 2009) Many cytoskeletal components such as actin filaments (McLean et al, 1995), microtubules (Heinlein et al, 1995), and the microtubuleassociated proteins MPB2C (Kragler et al, 2003) and EB1a (Brandner et al, 2008) interact with TMV MP. We show that RbCS plays an essential role in virus movement, host susceptibility, and Tm-22-

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