Brassinosteroid Involvement in Arabidopsis thaliana Stomatal Opening

Abstract

Stomata within the plant epidermis regulate CO2 uptake for photosynthesis and water loss through transpiration. Stomatal opening in Arabidopsis thaliana is determined by various factors, including blue light as a signal and multiple phytohormones. Plasma membrane transporters, including H+-ATPase, K+ channels and anion channels in guard cells, mediate these processes, and the activities and expression levels of these components determine stomatal aperture. However, the regulatory mechanisms involved in these processes are not fully understood. In this study, we used infrared thermography to isolate a mutant defective in stomatal opening in response to light. The causative mutation was identified as an allele of the brassinosteroid (BR) biosynthetic mutant dwarf5. Guard cells from this mutant exhibited normal H+-ATPase activity in response to blue light, but showed reduced K+ accumulation and inward-rectifying K+ (K+in) channel activity as a consequence of decreased expression of major K+in channel genes. Consistent with these results, another BR biosynthetic mutant, det2-1, and a BR receptor mutant, bri1-6, exhibited reduced blue light-dependent stomatal opening. Furthermore, application of BR to the hydroponic culture medium completely restored stomatal opening in dwarf5 and det2-1 but not in bri1-6. However, application of BR to the epidermis of dwarf5 did not restore stomatal response. From these results, we conclude that endogenous BR acts in a long-term manner and is required in guard cells with the ability to open stomata in response to light, probably through regulation of K+in channel activity.

Drought-tolerant and drought-sensitive genotypes of maize (Zea mays L.) differ in contents of endogenous brassinosteroids and their drought-induced changes

“…While low concentrations of exogenously applied BRs do not affect stomatal movements, higher BR concentrations can operate in two opposite ways. They either induce stomatal closure [ 105 , 106 ] or, conversely, facilitate the opening of the stomata whose closure was induced by ABA [ 107 ] or impaired by BR deficiency [ 108 ]. It is thus possible that the observed differences in the endogenous BR levels in the leaves of our two maize genotypes could perhaps be somehow connected to the behaviour of their stomata.…”

RETRACTED: OST1 Activation by the Brassinosteroid-Regulated Kinase CDG1-LIKE1 in Stomatal Closure

“…These implicate that the functional orientation of BR in stomatal movement might be influenced by BR contents. In addition, Inoue et al (2017) showed that BRdeficient mutants (dwf5 and det2-1) has impaired blue lightinduced stomatal opening. Notably, the compromised stomatal opening of the dwf5 mutant was recovered by long-term application of BL (3 weeks) but not by short-term application of BL (4 h).…”

Genes for ash tree resistance to an insect pest identified via comparative genomics

“…There is also evidence for a role for brassinosteriods in regulating glucosinolate profiles, which function in defence response against insects in A. thaliana 192 . The det2-1 mutant in A. thaliana has impaired stomatal opening in response to blue light, suggesting a further possible role for brassinosteroids in stomatal opening 193 . One of the apparent orthologues of OG43828/FRAEX38873_v2_000227880 in P. trichocarpa, Potri.T122200 ( Supplementary Fig.…”