# TGG1 and TGG2 mutations impair allyl isothiocyanate-mediated stomatal closure in Arabidopsis thaliana

## TL;DR

This study shows that TGG1 and TGG2 proteins are involved in signaling for stomatal closure in plants when exposed to a specific compound called allyl isothiocyanate.

## Contribution

The study reveals that TGG1 and TGG2 are part of the signaling pathway for allyl isothiocyanate-induced stomatal closure, independent of their enzymatic activity.

## Key findings

- TGG1 and TGG2 are involved in allyl isothiocyanate signaling for stomatal closure in Arabidopsis.
- The double mutant tgg1 tgg2 fails to respond to allyl isothiocyanate for stomatal closure.
- AITC induces reactive oxygen species and calcium oscillations in guard cells regardless of TGG1/TGG2 presence.

## Abstract

Myrosinase, referred to as thioglucoside glucohydrolase (TGG), plays a crucial role in plant physiology through catalyzing the hydrolysis of glucosinolates into bioactive isothiocyanates. In Arabidopsis thaliana, the myrosinases TGG1 and TGG2 are essential for abscisic acid- and methyl jasmonate-induced stomata closure. Allyl isothiocyanate (AITC), one of myrosinase products, triggers stomatal closure in A. thaliana. We investigated stomatal responses to AITC to clarify the role of TGG1 and TGG2 in Arabidopsis guard-cell signaling. Allyl isothiocyanate at 50 μM and 100 μM induced stomatal closure in the tgg1 and tgg2 single mutants but not in the tgg1 tgg2 double mutant. Furthermore, AITC at 50 μM induced the production of reactive oxygen species and nitric oxide, cytosolic alkalization, and oscillations in cytosolic free calcium concentration in guard cells of both wild-type and mutant plants. These findings suggest that TGG1 and TGG2 are involved in AITC signaling pathway through interaction with signal component(s) downstream of these signaling events, which is not accompanied by hydrolysis of glucosinolates because of the difference in subcellular localization between enzymes (myrosinases) and substrates (glucosinolates).

The online version contains supplementary material available at 10.1007/s00709-025-02039-z.