| 1. |
- Jurca, Manuela, et al.
(författare)
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ZEITLUPE Promotes ABA-Induced Stomatal Closure in Arabidopsis and Populus
- 2022
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Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Plants balance water availability with gas exchange and photosynthesis by controlling stomatal aperture. This control is regulated in part by the circadian clock, but it remains unclear how signalling pathways of daily rhythms are integrated into stress responses. The serine/threonine protein kinase OPEN STOMATA 1 (OST1) contributes to the regulation of stomatal closure via activation of S-type anion channels. OST1 also mediates gene regulation in response to ABA/drought stress. We show that ZEITLUPE (ZTL), a blue light photoreceptor and clock component, also regulates ABA-induced stomatal closure in Arabidopsis thaliana, establishing a link between clock and ABA-signalling pathways. ZTL sustains expression of OST1 and ABA-signalling genes. Stomatal closure in response to ABA is reduced in ztl mutants, which maintain wider stomatal apertures and show higher rates of gas exchange and water loss than wild-type plants. Detached rosette leaf assays revealed a stronger water loss phenotype in ztl-3, ost1-3 double mutants, indicating that ZTL and OST1 contributed synergistically to the control of stomatal aperture. Experimental studies of Populus sp., revealed that ZTL regulated the circadian clock and stomata, indicating ZTL function was similar in these trees and Arabidopsis. PSEUDO-RESPONSE REGULATOR 5 (PRR5), a known target of ZTL, affects ABA-induced responses, including stomatal regulation. Like ZTL, PRR5 interacted physically with OST1 and contributed to the integration of ABA responses with circadian clock signalling. This suggests a novel mechanism whereby the PRR proteins—which are expressed from dawn to dusk—interact with OST1 to mediate ABA-dependent plant responses to reduce water loss in time of stress.
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| 2. |
- Matrosova, Anastasia
(författare)
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New insights into the regulation of stomatal movements by red light, carbon dioxide and circadian rhythms
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stomata are small adjustable pores formed by pairs of guard cells that enable gas exchange between leaves and the atmosphere, thus directly affecting water loss and CO₂ uptake in plants. The current work focuses on the regulation of stomatal movements by red light, carbon dioxide and the circadian system and attempts to uncover molecular mechanisms that control guard cell function. The signaling pathway that underlays stomatal opening in response to red light is yet to be fully elucidated. Here, the HIGH LEAF TEMPERATURE 1 (HT1) protein kinase, known as a negative regulator of high CO₂ stomatal closure, is shown to be a key component of stomatal signaling in response to red light (Paper I). It was demonstrated that HT1 is epistatic to the positive regulator of ABA- and high CO₂-induced stomatal closure OPEN STOMATA1 (OST1) protein kinase both in red light- and CO₂-induced signal transduction in guard cells (Paper I). A photosynthesis-induced drop in intercellular [CO₂] as well as processes originating in the photosynthetic electron transport chain (PETC) have been proposed to signal the guard cell response to red light. Investigation of the effect of PETC inhibitors on stomatal conductance in Arabidopsis thaliana ecotypes Col-0 and Ely-1a has suggested the redox state of plastoquinone (PQ) pool to be involved in the regulation of stomatal movements (Paper II). The full mechanisms that link the regulation of stomatal movements to the circadian clock are yet unknown. The blue light receptor, F-box protein and key element of the circadian clock ZEITLUPE (ZTL) was here shown to physically interact with OST1 protein kinase (Paper III). Furthermore, Arabidopsis thaliana mutant plants and Populus transgenic lines that lack the activity of ZTL or OST1 demonstrated similar phenotypes, affected in stomatal movement control (Paper III). The work supports a requirement of both ZTL and OST1 in the regulation of guard cell turgor and suggests a direct link between the circadian clock and OST1 activity.
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| 3. |
- Matrosova, Anastasia, et al.
(författare)
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The HT1 protein kinase is essential for red light-induced stomatal opening and genetically interacts with OST1 in red light and CO2-induced stomatal movement responses
- 2015
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 208, s. 1126-1137
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Tidskriftsartikel (refereegranskat)abstract
- The question of whether red light-induced stomatal opening is mediated by a photosynthesis-derived reduction in intercellular [CO2] (C-i) remains controversial and genetic analyses are needed.The Arabidopsis thaliana protein kinase HIGH TEMPERATURE 1 (HT1) is a negative regulator of [CO2]-induced stomatal closing and ht1-2 mutant plants do not show stomatal opening to low [CO2]. The protein kinase mutant ost1-3 exhibits slowed stomatal responses to CO2. The functions of HT1 and OPEN STOMATA 1 (OST1) to changes in red, blue light or [CO2] were analyzed. For comparison we assayed recessive ca1ca4 carbonic anhydrase double mutant plants, based on their slowed stomatal response to CO2.Here, we report a strong impairment in ht1 in red light-induced stomatal opening whereas blue light was able to induce stomatal opening. The effects on photosynthetic performance in ht1 were restored when stomatal limitation of CO2 uptake, by control of [C-i], was eliminated. HT1 was found to interact genetically with OST1 both during red light-and low [CO2]-induced stomatal opening. Analyses of ca1ca4 plants suggest that more than a low [C-i]-dependent pathway may function in red light-induced stomatal opening.These results demonstrate that HT1 is essential for red light-induced stomatal opening and interacts genetically with OST1 during stomatal responses to red light and altered [CO2].
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| 4. |
- Matrosova, Anastasia
(författare)
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The role of HT1 protein kinase in red light-induced stomatal opening
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Red light and blue light induce stomatal opening in plants via separate pathways. It is unclear to what extent photosynthetic processes, if any, of guard cells or underlying mesophyll are involved in the red light-induced stomatal response. The HT1 protein kinase is a negative regulator of high CO2-induced stomatal closure and the ht1 mutant responds to blue light and ABA. If the red light signal is transduced via a change in photosynthetic activity, this mediator signal could be an altered intercellular [CO2]. Due to the stomatal CO2 insensitivity in ht1, this mutant was analyzed for its role in red light-induced stomatal opening. Gas exchange measurements of stomatal conductance showed a lack of functional red light stomatal opening in ht1-1 and ht1-2, while ht1 alleles exhibited stomatal opening under blue light. In order to examine photosynthesis processes, measurements of photosynthetic assimilation, several fluorescent parameters and a net carbon assimilation assay were performed. The results show that mesophyll photosynthesis is largely functional in ht1-2 both for light-dependent and Calvin Cycle-dependent reactions. Despite red light illumination, fusicoccin induced H+-ATPase activity and stomatal opening in ht1 mutant as examined by microscopy-based bioassays. To assay whether other red-light triggered processes are functional in ht1 mutants, the de-etiolation response was investigated. The wild-type response of ht1 suggested that an impaired phytochrome B performance is not the cause for an impaired red light stomatal response. In addition, a method to perform guard cell protoplasts isolation was established for use in future cell-specific applications. Putting the findings in perspective led to a model in which HT1 functions within guard cells as a positive mediator of red light and low CO2 control of stomatal opening, where HT1 acts prior to H+-ATPase activation.
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