AUTHOR=Zhang Kaixin , Su Hongzhu , Zhou Jianxin , Liang Wenjie , Liu Desheng , Li Jing 

TITLE=Overexpressing the Myrosinase Gene TGG1 Enhances Stomatal Defense Against Pseudomonas syringae and Delays Flowering in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01230

DOI=10.3389/fpls.2019.01230

ISSN=1664-462X

ABSTRACT=<p>Myrosinase enzymes and their substrate glucosinolates provide a specific defensive mechanism against biotic invaders in the Brassicaceae family. In these plants, myrosinase hydrolyzes glucosinolates into diverse products, which can have direct antibiotic activity or function as signaling molecules that initiate a variety of defense reactions. A myrosinase, β-thioglucoside glucohydrolase 1 (TGG1) was previously found to be strikingly abundant in guard cells, and it is required for the abscisic acid (ABA) response of stomata. However, it remains unknown which particular physiological processes actually involve stomatal activity as modulated by TGG1. In this experimental study, a homologous <italic>TGG1</italic> gene from broccoli (<italic>Brassica oleracea</italic> var. <italic>italica</italic>), <italic>BoTGG1</italic>, was overexpressed in <italic>Arabidopsis</italic>. The transgenic plants showed enhanced resistance against the bacterial pathogen <italic>Pseudomonas syringae</italic> pv. <italic>tomato</italic> (<italic>Pst</italic>) DC3000 <italic>via</italic> improved stomatal defense. Upon <italic>Pst</italic> DC3000 infection, overexpressing <italic>BoTGG1</italic> accelerated stomatal closure and inhibited the reopening of stomata. Compared with the wild type, <italic>35S::BoTGG1</italic> was more sensitive to ABA- and salicylic acid (SA)-induced stomatal closure but was less sensitive to indole-3-acetic acid (IAA)-inhibited stomatal closure, thus indicating these hormone signaling pathways were possibly involved in stomatal defense regulated by TGG1. Furthermore, overexpression of <italic>BoTGG1</italic> delayed flowering by promoting the expression of <italic>FLOWERING LOCUS C</italic> (<italic>FLC</italic>), which encodes a MADS-box transcription factor known as floral repressor. Taken together, our study’s results suggest glucosinolate metabolism mediated by TGG1 plays a role in plant stomatal defense against <italic>P. syringae</italic> and also modulates flowering time by affecting the FLC pathway.</p>