# Nicotiana tabacum Kunitz Peptidase Inhibitor-like Protein Regulates Intercellular Transport

## TL;DR

This paper identifies a protein in tobacco plants that regulates cell-to-cell transport and responds to stress and viral infections.

## Contribution

The study characterizes NtKPILP, a stress-responsive protein in Nicotiana tabacum, and its role in plasmodesmata regulation.

## Key findings

- NtKPILP is highly expressed in roots, flowers, and seeds but not in leaves of intact plants.
- NtKPILP mRNA accumulates in leaves under stress and viral infection.
- NtKPILP downregulation reduces macromolecule transport and increases callose deposition at plasmodesmata.

## Abstract

A coordinated and generalized plant response to adverse environmental factors largely depends on the proper and finely-tuned regulation of intercellular transport via plasmodesmata (PD). However, the knowledge of the whole network of PD-controlling mechanisms is far from complete. Earlier, a cellular factor, Kunitz peptidase inhibitor-like protein (KPILP), that affects PD gating and plays a proviral role, was identified in Nicotiana benthamiana plants. Here we characterized its homolog from N. tabacum, NtKPILP, which is hardly detectable in leaves of intact plants, in contrast to roots, flowers and seeds where NtKPILP is highly expressed. However, its mRNA accumulation in leaves increases in response to various stresses, including viral infection. NtKPILP was demonstrated to affect chloroplast functioning. Using the virus-induced gene silencing approach, we have shown that NtKPILP downregulation negatively affects intercellular transport of macromolecules, inducing callose deposition at PD and suppressing beta-1,3-glucanase mRNA accumulation. Together, the obtained results indicate that NtKPILP is a viral infection-responsive cellular factor that is involved in PD permeability regulation, sharing thus the features of KPILPs from other Nicotiana species.