THI1, a Thiamine Thiazole Synthase, Interacts with Ca2+-Dependent Protein Kinase CPK33 and Modulates the S-Type Anion Channels and Stomatal Closure in Arabidopsis  

Abstract

Thiamine is required for both plant growth and development. Here, the involvement of a thiamine thiazole synthase, THI1, has been demonstrated in both guard cell abscisic acid (ABA) signaling and the drought response in Arabidopsis (Arabidopsis thaliana). THI1 overexpressors proved to be more sensitive to ABA than the wild type with respect to both the activation of guard cell slow type anion channels and stomatal closure; this effectively reduced the rate of water loss from the plant and thereby enhanced its level of drought tolerance. A yeast two-hybrid strategy was used to screen a cDNA library from epidermal strips of leaves for THI1 regulatory factors, and identified CPK33, a Ca 2+ -dependent protein kinase, as interactor with THI1 in a plasma membrane-delimited manner. Loss-of-function cpk33 mutants were hypersensitive to ABA activation of slow type anion channels and ABA-induced stomatal closure, while the CPK33 overexpression lines showed opposite phenotypes. CPK33 kinase activity was essential for ABA-induced stomatal closure. Consistent with their contrasting regulatory role over stomatal closure, THI1 suppressed CPK33 kinase activity in vitro. Together, our data reveal a novel regulatory role of thiamine thiazole synthase to kinase activity in guard cell signaling.

The Arabidopsis guard cell outward potassium channel GORK is regulated by CPK33

“…However, CPK33 has been reported as a negative regulator of stomatal closure under ABA application [40]. Loss of function of CPK33 enhances ABA-induced anion currents, whereas overexpression of CPK33 inhibits ABA-induced anion currents [40]. CPK33 has an opposite effect on anion current regulation in guard cells compared to CPK6, CPK21, and CPK23 [17,18,31].…”

“…The cpk4 and cpk11 mutant plants were impaired in ABA‐responsive gene expression suggesting both are positive regulators involved in the Ca 2+ ‐dependent ABA signaling . The CPK33 function in stomatal movements was recently shown . Indeed, cpk33 mutant displays strong ABA‐induced anionic currents.…”

Properties and functions of calcium‐dependent protein kinases and their relatives in Arabidopsis thaliana

“…Given that OST1, CPKs and CIPKs redundantly activate SLAC1 on S59 and S120 (Maierhofer et al ., ; Brandt et al ., ), the above results suggest that higher order mutants are required to unveil the CPK contribution to stomatal regulation in planta beside OST1 and CIPKs. By contrast, CPK9/33 were identified as redundant negative regulators of ABA‐induced stomatal closure and S‐type currents, consistent with drought resistance of cpk33 and sensitivity of CPK33‐overexpressors (Li et al ., ; Chen et al ., ).…”

The Membrane Transport System of the Guard Cell and Its Integration for Stomatal Dynamics

“…Functions listed relate to the kinase group as a whole, not necessarily to the specific kinase on the same line of text. References are as follows: A (Pei et al, 1996;Mori et al, 2006;Zhu et al, 2007;Geiger et al, 2010;Zou et al, 2010Zou et al, , 2015Ronzier et al, 2014;Brandt et al, 2015;Li et al, 2016);B (Fujii et al, 2009;Geiger et al, 2009;Lee et al, 2009;Park et al, 2009;Sato et al, 2009;Sirichandra et al, 2009;Umezawa et al, 2009;Imes et al, 2013;Osakabe et al, 2013;Wege et al, 2014;Grondin et al, 2015;Yin et al, 2016); C (Guo et al, 2002;Ohta et al, 2003;Xu et al, 2006;Cheong et al, 2007;Held et al, 2011;Maierhofer et al, 2014); D (Gosti et al, 1999;Merlot et al, 2001;Chérel et al, 2002;Leonhardt et al, 2004;Saez et al, 2004Saez et al, , 2006Kuhn et al, 2006;Yoshida et al, 2006;Ma et al, 2009;Park et al, 2009;Rubio et al, 2009;Lan et al, 2011;Brandt et al, 2015;Lefoulon et al, 2016;…”