The rubisco small subunit is involved in tobamovirus movement and Tm-2²-mediated extreme resistance

Area of Science:

• Plant Pathology
• Molecular Plant-Virus Interactions
• Biochemistry

Background:

• The movement protein (MP) of Tomato mosaic tobamovirus (ToMV) is essential for viral spread, symptom development, and plant immune responses.
• The precise mechanisms by which ToMV MP executes these diverse functions remain incompletely understood.

Purpose of the Study:

• To investigate the interaction between ToMV MP and host factors in Nicotiana benthamiana.
• To elucidate the role of the Rubisco small subunit (RbCS) in ToMV infection and plant defense.

Main Methods:

• In vitro and in vivo interaction assays between ToMV MP and Nicotiana benthamiana RbCS (NbRbCS).
• Gene silencing of NbRbCS in susceptible and Tm-2² transgenic Nicotiana benthamiana plants.
• Assessment of ToMV local infectivity, systemic movement, and symptom development.

Main Results:

• ToMV MP directly interacts with NbRbCS in both in vitro and in vivo conditions.
• Silencing NbRbCS in susceptible plants enhanced local ToMV infection (necrosis) but delayed systemic spread.
• In Tm-2² resistant plants, NbRbCS silencing compromised extreme resistance, allowing local infection but preventing systemic movement.

Conclusions:

• NbRbCS is a key host factor involved in facilitating tobamovirus cell-to-cell movement.
• NbRbCS plays a significant role in supporting plant antiviral defenses against ToMV.
• Targeting NbRbCS could be a strategy to modulate plant resistance to tobamoviruses.