# Chloroplast Fibrillin‐Mediated α‐Tocopherol Biosynthesis Impaired by a Virus to Enhance Infection and to Improve Drought Tolerance

## TL;DR

A virus uses a protein to target chloroplast structures, impair vitamin E production, and enhance both its infection and the plant's drought tolerance.

## Contribution

Discovery of a viral protein that manipulates chloroplast lipid droplets to impair α-tocopherol biosynthesis and promote drought tolerance.

## Key findings

- ToCV's p22 protein binds to FBN1.1, reducing plastoglobule size and α-tocopherol production.
- Reduced α-tocopherol increases ROS, aiding viral infection and triggering drought tolerance via PAP accumulation.
- FBN1.1 regulates interactions between plant, virus, and drought stress through PG function.

## Abstract

Plastoglobules (PGs), the lipid droplets mainly within chloroplasts, are crucial for plant redox homeostasis and environmental adaptation. However, the regulation of PG under stress remains elusive. This study uncovers that PGs are targeted by the p22 protein encoded by an emerging virus‐tomato chlorosis virus (ToCV), leading to impaired α‐tocopherol biosynthesis, thereby facilitating viral infection and improving drought resistance. Specially, ToCV‐encoded p22 protein co‐opts the PG structural protein fibrillin (FBN) to access PG, where it impairs α‐tocopherol biosynthesis via disturbing the interaction between FBN1.1 and tocopherol cyclase (VTE1). Alpha‐tocopherol is required for both preventing lipid peroxidation in the thylakoid membrane and suppressing ToCV infection. Infection of ToCV or transgenic expression of p22 protein inhibits α‐tocopherol biosynthesis, resulting in chloroplast oxidative stress, which may contribute to the accumulation of 3′‐phosphoadenosine 5′‐phosphate (PAP), a retrograde signal from chloroplasts to the nucleus that triggers drought tolerance. Taken together, FBN1.1 modulates plant‐virus‐drought interaction via regulating the function of PG.

ToCV‐encoded p22 targets chloroplast plastoglobules (PGs) via directly binding PG structural protein FBN1.1, reducing the size of PG and inhibiting α‐tocopherol biosynthesis via competing with tocopherol cyclase (VTE1). Consequently, the elevated chloroplast ROS not only creates a suitable cellular environment for efficient ToCV infection but also stimulates PAP accumulation, a retrograde signal from chloroplasts to the nucleus that triggers drought tolerance.