Biology subjects

Gehring, C.

Publications and source records attributed to Gehring, C..

7 recordsLinked to original sources

bioRxiv2026

Abscisic acid binds to an Arabidopsis thaliana phosphodiesterase and tunes its activity

Growing evidence suggests that plant proteomes contain numerous proteins that specifically bind abscisic acid (ABA). Many of them are complex multidomain proteins where specific ABA-binding can cause biochemical and physiological changes. Here we show that the Arabidopsis thaliana K+ transporter AtKUP5 contains both a functional cytoplasmic N-terminal adenylate cyclase (AC) enabling the synthesis of 3,5-cAMP from ATP and a C-terminal phosphodiesterase (PDE) that hydrolyses 3,5-cAMP to 5-AMP. We found that ABA binds in a ligand-specific manner to the catalytic center of the PDE thereby causing a reduction of 3,5-cAMP hydrolysis in vitro. The hydrolytic activity of the PDE is ABA concentration-dependent, biphasic and requires the presence of an intact ABA-binding site similar to the one in the canonical Pyrabactin resistance 1/PYR-like/Abscisic acid receptors, with Vmax of 1.19 pmole min{square}1 g{square}1 in the absence of ABA, increasing to 1.58 pmole min{square}1 g{square}1 at 2 nM ABA, and decreasing to 0.75 pmole min{square}1 g{square}1 at 50 nM ABA. These findings are therefore consistent with a direct role of ABA in PDE activity modulations and form a functional link between 3,5-cAMP signaling and K+ flux. Furthermore, we predict that a growing number of such receptor-like proteins that specifically and directly interact with ABA will be discovered thereby uncovering complex and ancient layers of signaling and metabolic regulation.

plant biology↗

bioRxiv2025

Identification of molecular mechanisms contributing to acquired thermotolerance by transcriptome profiling

Heat stress poses a serious threat to plant survival and productivity, and has a direct influence on crop yield stability. Plants response to high temperature is tightly controlled by complex genetic networks. Plants can be acclimated through gradual pre-exposure to increasing temperatures and that in turn causes higher survival in subsequent and otherwise lethal heat stress conditions. To investigate the physiological and molecular processes underlying heat acclimation and recovery, we examined changes in Arabidopsis thaliana transcriptome throughout the acclimation and the subsequent heat shock treatment. Groups of differentially expressed genes and enriched biological pathways that constitute the heat transcriptional memory were identified. The function of flavonoids in plant heat stress were further explored experimentally. In addition, we observed altered stomata density and aperture responses in heat acclimated plants, and this might be partially controlled by AGAMOUS-LIKE16 (AGL16) transcription factor and its negative regulator microRNA824 (miR824).

plant biology↗

bioRxiv2025

Delineating plant responses to the 3',5'- and 2',3'-cAMP isomers

Similar to animals, both the 3,5- and the 2,3-cAMP isomers are present in plants. The former is the enzymatic product of adenylate cyclases (ACs), the latter is an RNA degradation product. While there is increasing evidence that both isomers can elicit or modulate a broad range of physiological responses, the question of isomer specificity of responses has remained largely unresolved. To delineate isomer-specific responses in Arabidopsis thaliana at the systems level, we have combined a comparative proteomics and electrophysiological approaches. Both isomers cause distinct systemic effects on the proteome, with the 2,3 isomer notably affecting systems-level functions like transcriptional regulation. None of the isomers affects net ion fluxes in the root under control conditions, but both were able to attenuate the magnitude of oxidative stress-induced K+ net loss and Ca2+ uptake by 2-fold. Isomer-specific responses of single molecular targets were assessed in the cyclic nucleotide-gated channels 2 and 18 (CNGC2 and CNGC18). Both channels are gated by the 3,5-cAMP isomer only, suggesting that the gating is isomer-specific and this implies that gating in vivo depends on catalytically active ACs. HighlightsDistinct Arabidopsis responses to 3,5- and 2,3-cAMP uncover isomer-specific molecular targets and physiological effects in cyclic nucleotide signaling.

plant biology↗

bioRxiv2021

Moonlighting adenylyl cyclases in plants: an Arabidopsis thaliana 9-cis-epoxycarotenoid dioxygenase as point in case

Adenylyl cyclases (ACs) and their catalytic product cAMP are regulatory components of plant responses. AC domains are intrinsic components of complex molecules with multiple functions, some of which are co-regulated by cAMP. Here we used an amino acid search motif based on annotated ACs in organisms across species to identify 12 unique Arabidopsis thaliana candidate ACs, four of which have a role in the biosynthesis of the stress hormone abscisic acid (ABA). One of these, the 9-cis-epoxycarotenoid dioxygenase (NCED3, At3g14440), was identified by sequence and structural analysis as a putative AC and then tested experimentally for activity. We show that an NCED3 AC fragment can complement an AC deficient E. coli mutant and this rescue is nullified when key amino acids in the AC motif are mutated. AC activity was also confirmed by tandem liquid chromatography mass spectrometry (LC-MS/MS). Our results are consistent with a moonlighting role for mononucleotide cyclases in multi-domain proteins that have at least one other distinct molecular function such as catalysis or ion channel activation and promise to yield new insights into tuning mechanisms of ABA dependent plant responses. Finally, our search method can also be applied to discover ACs in other species including Homo sapiens. HighlightsO_LIAn adenylyl cyclase (AC) catalytic center motif identifies novel ACs in plants C_LIO_LIACs can moonlight in complex proteins with other enzymatic domains C_LIO_LIA 9-cis-epoxycarotenoid dioxygenase essential for abscisic acid synthesis contains an AC C_LIO_LIThis finding implicates cAMP in abscisic acid synthesis and signaling C_LI

plant biology↗

bioRxiv2020

Arginine citrullination of proteins as a specific response mechanism in Arabidopsis thaliana

Arginine deamination, also referred to as citrullination of proteins by peptidyl-arginine deiminases, is a post-translational modification affecting histone modifications, epigenetic transcriptional regulation and proteolysis in animals, but has not been reported in higher plants. Here we report, firstly, that Arabidopsis thaliana proteome contains proteins with a specific citrullination signature and that many of the citrullinated proteins have nucleotide-binding regulatory functions. Secondly, we show that changes in the citrullinome occur in response to cold stress, and thirdly, we identify an Arabidopsis thaliana protein with calcium-dependent arginine deiminase activity. Taken together, these findings establish this post-translational modification as a hitherto neglected component of cellular reprogramming during stress responses.

plant biology↗

bioRxiv2020

Mg2+ modulates the activity of hyperpolarization-activated calcium currents in plant cells

Hyperpolarization-activated calcium channels (HACCs) are found in the plasma membrane and tonoplast of many plant cell types where they have an important role in Ca2+-dependent signaling. The unusual gating properties of HACCs in plants, i.e., activation by membrane hyperpolarization rather than depolarization, dictates that HACCs are normally open at physiological hyperpolarized resting membrane potentials (the so called pump or P-state), thus, if not regulated, they would be continuously leaking Ca2+ into cells. In guard cells, HACCs are permeable to Ca2+, Ba2+ and Mg2+, activated by H2O2 and the plant hormone abscisic acid (ABA) and their activity is greatly reduced by low amounts of free cytosolic Ca2+ ([Ca2+]Cyt) and hence will close during [Ca2+]Cyt surges. Here we demonstrate that the presence of the commonly used Mg-ATP inside the cell greatly reduces HACC activity especially at voltages [≤] -200 mV and that Mg2+ causes this block. We therefore conclude, firstly, that physiological cytosolic Mg2+ levels affect HACCs gating and that channel opening requires either high negative voltages ([≥] -200 mV) and/or displacement of Mg2+ away from the immediate vicinity of the channel. Secondly, based on structural comparisons with Mg2+-sensitive animal inward-rectifying K+ channel, we propose that the likely candidate HACCS described here are cyclic nucleotide gated channels (CNGCs), many of which also contain a conserved di-acidic Mg2+-binding motif within their pores. This conclusion is consistent with the electrophysiological data. Finally, we propose that Mg2+, much like in animal cells, is an important component in Ca2+ signalling and homeostasis in plants.

plant biology↗

bioRxiv2019

The Arabidopsis Diacylglycerol Kinase 4 is involved in nitric oxide-dependent pollen tube guidance and fertilization

Nitric oxide (NO) is a key signaling molecule that regulates diverse biological processes in both animals and plants. In animals, NO regulates vascular wall tone, neurotransmission and immune response while in plants, NO is essential for development and responses to biotic and abiotic stresses [1-3]. Interestingly, NO is involved in the sexual reproduction of both animals and plants mediating physiological events related to the male gamete [2, 4]. In animals, NO stimulates sperm motility [4] and binding to the plasma membrane of oocytes [5] while in plants, NO mediates pollen-stigma interactions and pollen tube guidance [6, 7]. NO generation in pollen tubes (PTs) has been demonstrated [8] and intracellular responses to NO include cytosolic Ca2+ elevation, actin organization, vesicle trafficking and cell wall deposition [7, 9]. However, the NO-responsive proteins that mediate these responses are still elusive. Here we show that PTs of Arabidopsis lacking the pollen-specific Diacylglycerol Kinase 4 (DGK4) grow slower and become insensitive to NO-dependent growth inhibition and re-orientation responses. Recombinant DGK4 protein yields NO-responsive spectral and catalytic changes in vitro which are compatible with a role in NO perception and signaling in PTs. NO is a fast, diffusible gas and, based on our results, we hypothesize it could serve in long range signaling and/or rapid cell-cell communication functions mediated by DGK4 downstream signaling during the progamic phase of angiosperm reproduction.

plant biology↗