scholarly journals The role of strigolactones in regulation of stomatal conductance and plant-pathogen interactions inArabidopsis thaliana

2019 ◽  
Author(s):  
Maria Kalliola ◽  
Liina Jakobson ◽  
Pär Davidsson ◽  
Ville Pennanen ◽  
Cezary Waszczak ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stomatal Conductance ◽  
Pseudomonas Syringae ◽  
Guard Cell ◽  
Stomatal Closure ◽  
Cell Signalling ◽  
Guard Cells ◽  
Signalling Pathway ◽  
Ozone Sensitivity

AbstractStrigolactones are a group of phytohormones that control shoot branching inArabidopsis thaliana. However, in recent years they have been shown to affect many other plant processes. We previously showed that the strigolactone perception mutantmore axillary branches 2 (max2)has increased susceptibility to plant pathogenic bacteria as a result of more open stomata as well as alterations in hormonal signalling. Here we show that both, strigolactone biosynthesis- (max3andmax4), and perception mutants (max2anddwarf14) are significantly more sensitive toPseudomonas syringaeDC3000. Moreover, in response toP. syringaeinfection, high levels of SA accumulated inmax2and this mutant was ozone sensitive. To search for the mechanisms that could explain pathogen- and ozone sensitivity we performed gene expression analysis and several different assays that explore the function of guard cells and regulation of guard cell signalling.Treatments with GR24 (a strigolactone analogue) resulted in very modest changes in defence-related gene expression. In contrast, guard cell function was clearly impaired inmax2and depending on the assay used, also inmax3, max4andd14mutants. Moreover, stomatal responses to stimuli that cause stomatal closure in wild-type plants (darkness, high CO2and ABA) were analysed in the strigolactone mutants. In darkness both strigolactone biosynthesis and perception mutants showed reduced stomatal closure, whereas the response to high CO2was impaired only inmax2andd14. The response to ABA was not impaired in any of the mutants. To position the role of MAX2 in the guard cell signalling network,max2was crossed with mutants defective in ABA biosynthesis (aba2), in guard cell ABA signalling (ost1) and a scaffold protein required for proper ion channel activity (ghr1). The stomatal conductance of double mutants was consistently higher than the corresponding single mutants, suggesting that MAX2 acts in a signalling pathway that functions in parallel to the well characterized guard cell ABA signalling pathway. We propose that the impaired defence responses ofmax2is related to more open stomata that allows increased entry of bacteria or air pollutants like ozone. Furthermore, as MAX2 appears to act in a specific branch of guard cell signalling (related to CO2signalling), this protein could be one of the elusive components that allow guard cells to distinguish between different environmental conditions.

scholarly journals Gaining or cutting SLAC: the evolution of plant guard cell signalling pathways

2021 ◽  
Author(s):  
Frances C Sussmilch ◽  
Tobias Maierhofer ◽  
Johannes Herrmann ◽  
Lena J Voss ◽  
Christof Lind ◽  
...  
Keyword(s):  
Guard Cell ◽  
Stomatal Closure ◽  
Cell Signalling ◽  
Guard Cells ◽  
Land Plant ◽  
Signalling Pathways ◽  
Anion Channels ◽  
Plant Groups ◽  
Activation Mechanisms ◽  
Stomatal Movements

The evolution of adjustable plant pores (stomata), enabling CO2 acquisition in cuticle wax-sealed tissues was one of the most significant events in the development of life on land. But how did the guard cell signalling pathways that regulate stomatal movements evolve? We investigate this through comparison of fern and angiosperm guard cell transcriptomes. We find that these divergent plant groups share expression of similar genes in guard cells including biosynthesis and signalling genes for the drought stress hormone abscisic acid (ABA). However, despite conserved expression in guard cells, S-type anion channels from the SLAC/SLAH family — known for ABA-mediated stomatal closure in angiosperms — are not activated by the same pathways in ferns, highlighting likely differences in functionality. Examination of other land plant channels revealed a complex evolutionary history, featuring multiple gains or losses of SLAC activation mechanisms, as these channels were recruited to a role in stomatal closure. Taken together, the guard cells of flowering and non-flowering plants share similar core features, but also show lineage-specific and ecological niche-related adaptations, likely underlying differences in behaviour.

scholarly journals Structural and Functional Insights into the Role of Guard Cell Ion Channels in Abiotic Stress-Induced Stomatal Closure

Plants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 2774
Author(s):  
Hamdy Kashtoh ◽  
Kwang-Hyun Baek
Keyword(s):  
Ion Channels ◽  
Guard Cell ◽  
Stomatal Closure ◽  
Turgor Pressure ◽  
Anion Channel ◽  
Weather Conditions ◽  
Guard Cells ◽  
Water Transpiration ◽  
Structure And Functions

A stomatal pore is formed by a pair of specialized guard cells and serves as a major gateway for water transpiration and atmospheric CO2 influx for photosynthesis in plants. These pores must be tightly controlled, as inadequate CO2 intake and excessive water loss are devastating for plants. When the plants are exposed to extreme weather conditions such as high CO2 levels, O3, low air humidity, and drought, the turgor pressure of the guard cells exhibits an appropriate response against these stresses, which leads to stomatal closure. This phenomenon involves a complex network of ion channels and their regulation. It is well-established that the turgor pressure of guard cells is regulated by ions transportation across the membrane, such as anions and potassium ions. In this review, the guard cell ion channels are discussed, highlighting the structure and functions of key ion channels; the SLAC1 anion channel and KAT1 potassium channel, and their regulatory components, emphasizing their significance in guard cell response to various stimuli.

scholarly journals Overexpression of chloroplast-targeted ferrochelatase 1 results in a genomes uncoupled chloroplast-to-nucleus retrograde signalling phenotype

2020 ◽  
Vol 375 (1801) ◽  
pp. 20190401 ◽  
Author(s):  
Mike T. Page ◽  
Tania Garcia-Becerra ◽  
Alison G. Smith ◽  
Matthew J. Terry
Keyword(s):  
Gene Expression ◽  
Feedback Inhibition ◽  
Nuclear Gene ◽  
Signalling Pathway ◽  
Chloroplast Genes ◽  
Nuclear Gene Expression ◽  
Retrograde Signalling ◽  
Genes Encoding ◽  
Retrograde Signal

Chloroplast development requires communication between the progenitor plastids and the nucleus, where most of the genes encoding chloroplast proteins reside. Retrograde signals from the chloroplast to the nucleus control the expression of many of these genes, but the signalling pathway is poorly understood. Tetrapyrroles have been strongly implicated as mediators of this signal with the current hypothesis being that haem produced by the activity of ferrochelatase 1 (FC1) is required to promote nuclear gene expression. We have tested this hypothesis by overexpressing FC1 and specifically targeting it to either chloroplasts or mitochondria, two possible locations for this enzyme. Our results show that targeting of FC1 to chloroplasts results in increased expression of the nuclear-encoded chloroplast genes GUN4 , CA1 , HEMA1 , LHCB2.1, CHLH after treatment with Norflurazon (NF) and that this increase correlates to FC1 gene expression and haem production measured by feedback inhibition of protochlorophyllide synthesis. Targeting FC1 to mitochondria did not enhance the expression of nuclear-encoded chloroplast genes after NF treatment. The overexpression of FC1 also increased nuclear gene expression in the absence of NF treatment, demonstrating that this pathway is operational in the absence of a stress treatment. Our results therefore support the hypothesis that haem synthesis is a promotive chloroplast-to-nucleus retrograde signal. However, not all FC1 overexpression lines enhanced nuclear gene expression, suggesting there is still a lot we do not understand about the role of FC1 in this signalling pathway. This article is part of the theme issue ‘Retrograde signalling from endosymbiotic organelles’.

scholarly journals Downregulating VAC14 in Guard Cells Causes Drought Hypersensitivity by Inhibiting Stomatal Closure

2020 ◽  
Vol 11 ◽  
Author(s):  
Zong-Qi Wang ◽  
Qi Liu ◽  
Ju-Hua Wu ◽  
Juan Li ◽  
Jun-Min He ◽  
...  
Keyword(s):  
Stomatal Closure ◽  
Guard Cells ◽  
Land Plant ◽  
Scaffolding Protein ◽  
Stomatal Movement ◽  
Wild Type ◽  
Physiological Factors ◽  
Surrounding Environment ◽  
Intracellular Activities

Stomata are a key land plant innovation that permit the regulation of gaseous exchanges between the plant interior and the surrounding environment. By opening or closing, stomata regulate transpiration of water though the plant; and these actions are coordinated with acquisition of CO2 for photosynthesis. Stomatal movement is controlled by various environmental and physiological factors and associates with multiple intracellular activities, among which the dynamic remodeling of vacuoles plays a crucial role. Phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] is critical for dynamic remodeling of vacuoles. Its production requires a PI(3,5)P2-metabolizing complex consisting of FAB1/PIKfyve kinases, SAC phosphatases, and the scaffolding protein VAC14. Although genetic or pharmacological downregulation of PI(3,5)P2 causes hyposensitivity to ABA-induced stomatal closure, whether the effect of PI(3,5)P2 on stomatal movement is cell-autonomous and the physiological consequences of its reduction were unclear. We report that downregulating Arabidopsis VAC14 specifically in guard cells by artificial microRNAs (amiR-VAC14) results in enlarged guard cells and hyposensitivity to ABA- and dark-induced stomatal closure. Vacuolar fission during stomatal closure is compromised by downregulating VAC14 in guard cells. Exogenous application of PI(3,5)P2 rescued the amiR-VAC14 phenotype whereas PI(3,5)P2 inhibitor YM201636 caused wild-type plants to have inhibited stomatal closure. We further show that downregulating VAC14 specifically in guard cells impairs drought tolerance, suggestive of a key role of guard cell-produced PI(3,5)P2 in plant fitness.

scholarly journals Role of Jasmonic Acid Pathway in Tomato Plant-Pseudomonas syringae Interaction

Plants ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 136 ◽  
Author(s):  
Loredana Scalschi ◽  
Eugenio Llorens ◽  
Pilar García-Agustín ◽  
Begonya Vicedo
Keyword(s):  
Gene Expression ◽  
Salicylic Acid ◽  
Jasmonic Acid ◽  
Pseudomonas Syringae ◽  
Tomato Plant ◽  
Wild Type ◽  
Tomato Plants ◽  
Bacterial Pathogenicity ◽  
Acid Pathway

The jasmonic acid pathway has been considered as the backbone of the response against necrotrophic pathogens. However, a hemi-biotrophic pathogen, such as Pseudomonas syringae, has taken advantage of the crosstalk between the different plant hormones in order to manipulate the responses for its own interest. Despite that, the way in which Pseudomonas syringae releases coronatine to activate jasmonic acid-derived responses and block the activation of salicylic acid-mediated responses is widely known. However, the implication of the jasmonic intermediates in the plant-Pseudomonas interaction is not studied yet. In this work, we analyzed the response of both, plant and bacteria using SiOPR3 tomato plants. Interestingly, SiOPR3 plants are more resistant to infection with Pseudomonas. The gene expression of bacteria showed that, in SiOPR3 plants, the activation of pathogenicity is repressed in comparison to wild type plants, suggesting that the jasmonic acid pathway might play a role in the pathogenicity of the bacteria. Moreover, treatments with JA restore the susceptibility as well as activate the expression of bacterial pathogenicity genes. The observed results suggest that a complete jasmonic acid pathway is necessary for the susceptibility of tomato plants to Pseudomonas syringae.

How stomata resolve the dilemma of opposing priorities

1976 ◽  
Vol 273 (927) ◽  
pp. 551-560 ◽  
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Water Loss ◽  
Stomatal Closure ◽  
Guard Cells ◽  
Xanthium Strumarium ◽  
Solute Content ◽  
Stomatal Responses ◽  
Saturation Kinetics ◽  
Use Efficiency

Satisfaction of a leaf’s need for CO 2 requires an intensive gas exchange between mesophyll and atmosphere; prevention of excessive water loss demands that gas exchange be kept low. Stomata open when a low CO 2 concentration in the guard cells triggers ( a ) uptake of K + in exchange of H + , ( b ) production of organic acids, and ( c ) import of Cl - . ‘Hydropassive’ stomatal closure (i.e. turgor loss without reduction of the solute content of the guard cell) appears insufficient to protect the plant from desiccation. An additional ‘hydroactive’ solute loss is necessary; it is brought about by (+)-abscisic acid (ABA) acting as feedback messenger between mesophyll and epidermis. Stomatal closure not only curbs water loss but improves water-use efficiency because transpiration is proportional to stomatal conductance (at constant temperature). In contrast, assimilation, following saturation kinetics with respect to intercellular CO 2 , is relatively insensitive to changes in stomatal conductance (as long as stomata are wide open). In Xanthium strumarium , the amplitude of stomatal responses to ABA depends on the concentration of CO 2 in the guard cells; the opposite statement is also true. These interactions cause stomata to behave like ‘adjustable control systems’ capable of giving priority either to CO 2 assimilation or to water husbandry.

Ca2+ signalling in stomatal guard cells

2000 ◽  
Vol 28 (4) ◽  
pp. 476-481 ◽  
Author(s):  
M. R. McAinsh ◽  
J. E. Gray ◽  
A. M. Hetherington ◽  
C. P. Leckie ◽  
C. Ng
Keyword(s):  
Signal Transduction ◽  
Guard Cell ◽  
Signal Transduction Pathway ◽  
Guard Cells ◽  
Stomatal Opening ◽  
Cell Turgor ◽  
Stomatal Guard Cells ◽  
External Stimuli ◽  
Spatial And Temporal Characteristics

Ca2+ is a ubiquitous second messenger in the signal transduction pathway(s) by which stomatal guard cells respond to external stimuli. Increases in guard-cell cytosolic free Ca2+ concentration ([Ca2+]cyt) have been observed in response to stimuli that cause both stomatal opening and closure. In addition, several important components of Ca2+-based signalling pathways have been identified in guard cells, including the cADP-ribose and phospholipase C/Ins(1,4,5)P3-mediated Ca2+-mobilizing pathways. The central role of stimulus-induced increases in [Ca2+]cyt in guard-cell signal transduction has been clearly demonstrated in experiments examining the effects of modulating increases in [Ca2+]cyt on alterations in guard-cell turgor or the activity of ion channels that act as effectors in the guard-cell turgor response. In addition, the paradox that Ca2+ is involved in the transduction of signals that result in opposite end responses (stomatal opening and closure) might be accounted for by the generation of stimulus-specific Ca2+ signatures, such that increases in [Ca2+]cyt exhibit unique spatial and temporal characteristics.

Role of the protein kinase CIPK8 in guard cell signalling

2009 ◽  
Vol 153 (2) ◽  
pp. S210
Author(s):  
Deirdre H. McLachlan ◽  
Jorg Kudla ◽  
Alistair M. Hetherington
Keyword(s):  
Protein Kinase ◽  
Guard Cell ◽  
Cell Signalling
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