# Expression and antiviral application of exogenous lectin (griffithsin) in sweetpotatoes

## TL;DR

This study shows that exogenous griffithsin (GRFT) can be expressed in sweetpotatoes and helps protect against plant viruses by boosting antiviral gene activity.

## Contribution

The novel finding is that GRFT, when expressed in sweetpotatoes, effectively inhibits plant viruses without directly interacting with viral components.

## Key findings

- Transgenic sweetpotato plants expressing GRFT showed resistance to sweetpotato virus disease.
- GRFT inhibited sweetpotato leaf curl virus (SPLCV) replication in tobacco leaves at certain concentrations.
- GRFT activates antiviral-related genes in plants, even when it cannot bind carbohydrates.

## Abstract

Griffithsin (GRFT) is a highly effective, broad-spectrum, safe, and stable viral inhibitor used to suppress a variety of viruses. However, little information is available on whether GRFT can prevent plant viral diseases. In this study, we constructed a GRFT overexpression vector containing the sweetpotato storage cell signal peptide and generated exogenous GRFT overexpression lines through genetic transformation. The transgenic plants showed notable resistance to sweetpotato virus disease in the virus nursery. To verify the antiplant virus function of GRFT, transient expression in tobacco leaves showed that GRFT inhibited the sweetpotato leaf curl virus (SPLCV). The replication of SPLCV was entirely inhibited when the concentration of GRFT reached a certain level. The results of pulldown and BIFC assays showed that GRFT did not interact with the six components of SPLCV. In addition, the mutated GRFTD/A without the binding ability of carbohydrate and anticoronavirus function, in which three aspartate residues at carbohydrate binding sites were all mutated to alanine, also inhibited SPLCV. Quantitative reverse-transcription PCR analyses showed that the tobacco antiviral-related genes HIN1, ICS1, WRKY40, and PR10 were overexpressed after GRFT/GRFTD/A injection. Furthermore, HIN1, ICS1, and PR10 were more highly expressed in the leaves injected with GRFTD/A. The results suggest that sweetpotato is able to express GRFT exogenously as a bioreactor. Moreover, exogenous GRFT expression inhibits plant viruses by promoting the expression of plant antiviral genes.