ABA-glucose ester hydrolyzing enzyme ATBG1 and PHYB antagonistically regulate stomatal development

Abstract

The integration of conflicting signals in response to environmental constraints is essential to efficient plant growth and development. The light-dependent and the stress hormone abscisic acid (ABA)-dependent signaling pathways play opposite roles in many aspects of plant development. While these pathways have been extensively studied, the complex nature of their molecular dialogue is still obscure. When mobilized by the Arabidopsis thaliana β-glucosidase 1 (AtBG1), the glucose ester-conjugated inactive form of ABA has proven to be a source of the active hormone that is essential for the adaptation of the plant to water deficit, as evidenced by the impaired stomatal closure of atbg1 mutants in response to water stress. In a suppressor screen designed to identify the molecular components of AtBG1-associated physiological and developmental mechanisms, we identified the mutation variant of AtBG1 traits (vat1) , a new mutant allele of the red light/far-red light photoreceptor PHYTOCHROME B (PHYB) . Our study reveals that atbg1 plants harbor increased stomatal density in addition to impaired stomatal closure. We also provide evidence that the vat1/phyb mutation can restore the apparent transpiration of the atbg1 mutant by decreasing stomatal aperture and restoring a stomatal density similar to wild-type plants. Expression of key regulators of stomatal development showed a crosstalk between AtBG1-mediated ABA signaling and PHYB-mediated stomatal development. We conclude that the AtBG1-dependent regulation of ABA homeostasis and the PHYB-mediated light signaling pathways act antagonistically in the control of stomatal development.

Blue Light Improves Stomatal Function and Dark-Induced Closure of Rose Leaves (Rosa x hybrida) Developed at High Air Humidity

“…ABA-GE is believed to be a storage form of ABA, and can be stored in the vacuoles and hydrolyzed to free ABA when required ( Dietz et al., 2000 ; Arve, 2013 ). In many plant species it has been shown that ABA-GE is hydrolyzed in response to water stress, RH and darkness by β -glucosidase, leading to an increase in the pool of active ABA ( Dietz et al., 2000 ; Sauter et al., 2002 ; Lee et al., 2006 ; Arve, 2013 ; Allen et al., 2019 ). In roses, conjugation of ABA with glucose, creating ABA-GE seems to be a more important inactivation pathway than hydroxylation of ABA to PA ( Arve et al., 2013 ).…”

Influence of Environmental Factors Light, CO2, Temperature, and Relative Humidity on Stomatal Opening and Development: A Review

“…In the stt3a-2 mutant, which was inadequate in the transfer of N-glycan to peptides, the stability of the glycoprotein AtBG1 significantly decreased, leading to reduced ABA and auxin contents. ABA and auxin regulate downstream transcription factors of the stomatal lineage [24,25]. Reduced ABA and auxin contents associate with upregulation of SPCH, MUTE, and FAMA, leading to abnormal stomatal development in this mutant [21].…”

“…They showed that stomatal development was modulated by N-glycosylation through the regulation of the release of abscisic acid (ABA) and auxin by β-glucosidase activity [21][22][23]. Using the Arabidopsis gene AtBG1, which encodes a β-glucosidase of the glycoside hydrolase family 1, they showed that AtBG1 is a glycoprotein with three N-glycosylation sites [21,24]. In the stt3a-2 mutant, which was inadequate in the transfer of N-glycan to peptides, the stability of the glycoprotein AtBG1 significantly decreased, leading to reduced ABA and auxin contents.…”

Stomatal responses to carbon dioxide and light require abscisic acid catabolism in Arabidopsis

“…Arabidopsis thaliana (Arabidopsis) plants deficient in ABA biosynthesis or ABA perception and signalling can be compromised in their ability to shut their stomatal pores in response to elevated [CO 2 ] [10,11]; although other studies, while supporting a role for ABA, suggest that there is not a role for ABA receptors and some ABA signalling proteins [12][13][14][15]. ABA has also emerged as an important regulator of stomatal development [1,13,[16][17][18]. Growth of plants at elevated [CO 2 ] or in the presence of exogenous ABA generally results in plants with lower stomatal densities [17,[19][20][21][22].…”