Biology subjects

Shapiguzov, A.

Publications and source records attributed to Shapiguzov, A..

10 recordsLinked to original sources

bioRxiv2025

The EGY1-SGR1 module controls chloroplast development and senescence by modulating photosynthetic functions

The chloroplast plays essential roles not only in production of biochemical energy and metabolism, but also in plant development, including senescence. We describe a mutant with an unusual progression of senescence and identify it as an allele of ethylene-dependent gravitropism-deficient and yellow-green 1 (egy1-5). EGY1 encodes a chloroplast-localized metalloprotease that regulates chlorophyll metabolism. The single egy1-5 mutant exhibits defects in various aspects of chloroplast function, including abnormal accumulation of photosynthetic complexes, defects in photosynthetic electron transfer chain and altered responses to the chemicals methyl viologen and lincomycin. Additionally, egy1 lacks guard cell chloroplasts. We performed a suppressor mutant screen in the egy1 background to identify new regulators of senescence and chloroplast development. We found two suppressors that restored green leaves and mapping revealed that both suppressors had mutations in STAY-GREEN 1 (SGR1). SGR1 encodes the Mg2+ dechelatase enzyme, which catalyses the first step in chlorophyll breakdown. Several defects in the egy1 mutant were either fully or partially suppressed in egy1 sgr1. This enabled the function of EGY1 to be isolated, independent of the pleiotropic effects of chlorophyll degradation. Our findings suggest that chlorophyll homeostasis regulates the overall development and function of the chloroplast as well as plant senescence. HighlightIdentifying new mutants with defects in chlorophyll metabolism and chloroplast development shows that proper chlorophyll homeostasis is necessary for maintaining functional chloroplasts.

plant biology↗

bioRxiv2025

Linking stomatal function with photosynthetic light reactions and stress response in faba bean

Faba bean (Vicia faba L.) is a key protein crop, but its cultivation and yield stability are hindered by a number of environmental stresses. Stomata regulate gas exchange between the plant and atmosphere, playing a central role in photosynthesis and mediating plant responses to a wide range of environmental stressors. This study aimed to investigate variations in leaf temperature as a proxy for stomatal function and photosynthetic regulations in faba bean, and to examine the response of this crop to short-term acute ozone (O3) exposure stress. Here, we used a high-throughput plant phenotyping (HTPP) platform to screen 196 faba bean genotypes for photosynthetic and stomatal function under controlled conditions. A subset of extreme genotypes, identified based on relative leaf tempreture from the initial screening, was exposed to a 450 ppb O3 treatment. Our results revealed strong positive relationship between photosynthetic efficiency and relative leaf temperature. A three-fold difference in relative leaf temperature was observed among genotypes. The O3 treatment caused signicantly less damage in genotypes with higher leaf temperature compared to those with lower leaf temperature (p<0.001). By combining a HTPP platform with elevated O3 stress treatment, we identified faba bean genotypes with contrasting stomatal responses to the O3 exposure. Our results advance understanding of the regulation mechanisms of photosynthetic light reactions and the role of stomatal function in modulating faba bean responses to environmental stressors.

plant biology↗

bioRxiv2025

Photosynthetic adjustments maintain lettuce growth under dynamically changing lighting in controlled indoor farming setups

Studies have uncovered delicate mechanisms that enable plant acclimation to fluctuating light. Translating the knowledge to controlled environment agriculture could advance the development of cost-effective dynamic lighting strategies, but the effects of varying light intensities on vegetable crops remain poorly understood. Here we recorded chlorophyll fluorescence, photosynthetic activity, metabolic responses, and growth of lettuce (Lactuca sativa L.) cv. Katusa under dynamic lighting. The light intensity was varied at different times of the photoperiod with uniform daily light integral. Three setups, including a plant phenotyping facility, a small-scale vertical farm testbed and a larger-scale vertical farm were utilized to address the physiological responses and scalability of lighting strategies. We found that dynamic lighting supported lettuce cv. Katusa growth in all three indoor cultivation setups, even under artificial "split-night" regimes where the photoperiod was interrupted by two periods of darkness. The lettuce plants displayed delicate adjustments in photosynthetic light reactions and carbon metabolism, the latter of which followed the cumulative daily light integral under different lighting regimes. However, the overall metabolic composition of lettuce leaves did not respond to the changing light intensities. Our findings support the conclusion that dynamic lighting enables cost-effective lighting via optimization of electricity use in indoor cultivation. HighlightPhotosynthetic adjustments maintain lettuce (Lactuca sativa L.) cv. Katusa growth under dynamic lighting. This enables cost-effective cultivation via optimization of electricity use in controlled environment agriculture.

plant biology↗

bioRxiv2025

Protection of photosynthesis by UVR8 and cryptochromes in Arabidopsis under blue and UV radiation

Photosynthesis in plants is negatively affected by high light intensity and UV radiation. The photoreceptors UV RESISTANCE LOCUS 8 (UVR8) and CRYPTOCHROMES (CRYs) mediate perception and acclimation of plants to UV-B/UV-A2 (290-340 nm) and UV-A1/blue light (350-500 nm), respectively. However, their roles in photoprotection of photosynthesis across different wavebands of the spectrum remain unclear. Using chlorophyll fluorescence and LED lighting we studied the roles of UVR8 and CRYs in maintaining photosynthetic capacity in Arabidopsis exposed to UV-B, UV-A1, and blue light. Analysis of quantum yield of Photosystem II, non-photochemical quenching, and LHCII phosphorylation demonstrated that CRYs preserve photosynthetic performance in plants exposed to UV-B, UV-A1, and blue light. UVR8 and CRYs exhibit partially redundant functions in maintaining photosynthetic activity under UV-B, UV-A1, and blue light, and in preventing photodamage under high UV-A1 irradiance. Impaired UVR8 and CRY signaling reduced epidermal flavonol accumulation in leaves, which further compromised photoprotection. These findings provide valuable insights into how UV and blue light perception contribute to photoprotection, with broad implications for plant performance both in natural and managed environments.

plant biology↗

bioRxiv2024

Mitochondria affect photosynthesis through altered tissue levels of oxygen

Interactions between plant energy organelles, the chloroplasts and the mitochondria, are crucial for plant development and acclimation. These interactions occur at different levels including exchange of metabolites and reducing power, organelle signaling pathways and intracellular gas exchange. Mitochondrial retrograde stress signaling activates expression of nuclear genes encoding mitochondrial components, including alternative oxidases. High abundances of these respiratory enzymes coincide not only with the changes in plant respiration but also with alterations in the chloroplast. For example, plants that overexpress alternative oxidases are tolerant to methyl viologen, a redox-active compound that catalyzes transfer of electrons from Photosystem I to molecular oxygen. The mechanism of this inter-organelle interaction is unclear but could be related to diminished availability of tissue oxygen. Here we assessed respiration, photosynthesis and in vivo levels of oxygen in a set of Arabidopsis lines with perturbations in diverse mitochondrial functions, including defects in respiratory complex I, mitochondrial protein processing, transcription, nucleoid organization, altered fission and architecture or suppressed ATP synthase activity. In these lines, the increased abundance and activity of alternative oxidases strongly correlated with higher oxygen consumption in darkness, lower oxygen re-accumulation in light, and diminished effects of methyl viologen in chloroplasts. These results support the hypothesis that increased mitochondrial oxygen sink capacity affects photosynthesis by decreasing oxygen levels in tissues. This phenomenon can be one of the reasons for the impact that stressed mitochondria have on chloroplasts and photosynthesis. It contributes to our understanding of the mechanisms of hypoxia establishment and acclimation in plants.

plant biology↗

bioRxiv2021

Arabidopsis iron superoxide dismutase 1 protects against methyl viologen-induced oxidative stress in a copper-dependent manner

Iron superoxide dismutase 1 (FSD1) was recently characterized as a plastidial, cytoplasmic, and nuclear superoxide dismutase with osmoprotective and antioxidative functions. However, its role in oxidative stress tolerance is not well understood. Here, we characterized the role of FSD1 in response to methyl viologen (MV)-induced oxidative stress in Arabidopsis thaliana. The findings demonstrated that the antioxidative function of FSD1 depends on the availability of Cu2+ in growth media. Prolonged MV exposure led to a decreased accumulation rate of superoxide, higher levels of hydrogen peroxide production, and higher protein carbonylation in the fsd1 mutants and transgenic plants lacking a plastidial pool of FSD1, compared to the wild type. MV led to a rapid increase in FSD1 activity, followed by a decrease. Chloroplastic localization of FSD1 is necessary for these changes. Proteomic analysis showed that the sensitivity of the fsd1 mutants coincided with decreased abundance of ferredoxin and light PSII harvesting complex proteins, with altered levels of signaling proteins. Collectively, the study provides evidence for the conditional antioxidative function of FSD1 and its possible role in signaling.

plant biology↗

bioRxiv2020

Arabidopsis Poly(ADP-ribose)-binding protein RCD1 interacts with Photoregulatory Protein Kinases in nuclear bodies

Continuous reprogramming of gene expression in response to environmental signals is required for plant survival in changing environment. One mechanism responsible for this is signaling through hub proteins that integrate external stimuli and transcriptional responses. RADICAL-INDUCED CELL DEATH1 (RCD1) functions as a nuclear hub protein, that interacts with a variety of transcription factors through its C-terminal RST domain and acts as a co-regulator of numerous stress responses in plants. Here, a previously unknown function for RCD1 as a novel plant poly(ADP-ribose) (PAR) reader protein is described. RCD1 localizes to specific locations inside the nucleus, in a PAR-dependent manner; its N-terminal WWE domain o binds PAR and together with the PARP-like domain determines its localization to nuclear bodies (NBs), which is prevented by inhibition of PAR synthesis. RCD1 also interacts with Photoregulatory Protein Kinases (PPKs) that co-localize with RCD1 in the NBs. The PPKs, that have been associated with circadian clock, abscisic acid, and light signaling pathways, phosphorylate RCD1 at multiple sites in the intrinsically disordered region between the WWE and PARP-like domains. This affects its stability and functions in the nucleus and1 provides a mechanism where the turnover of a PAR-binding transcriptional co-regulator is controlled by nuclear protein kinases.

plant biology↗

bioRxiv2019

Increased expression of mitochondrial dysfunction stimulon genes affects chloroplast redox status and photosynthetic electron transfer in Arabidopsis

Mitochondrial retrograde signals control expression of nuclear mitochondrial dysfunction stimulon (MDS) genes. Although MDS gene products mostly affect mitochondrial functions, they also influence production of reactive oxygen species (ROS) and redox status of chloroplasts. To study this inter-organellar interaction, we analysed the response of the Arabidopsis MDS-overexpressor mutant rcd1 to methyl viologen (MV), which catalyses electron transfer from Photosystem I (PSI) to molecular oxygen, generating ROS in Mehlers reaction. The response of plants to MV was investigated by imaging chlorophyll fluorescence in aerobic and hypoxic environments, and by membrane inlet mass spectrometry. Hypoxic treatment abolished the effect of MV on photosynthetic electron transfer in rcd1, but not in wild type. A similar reaction to hypoxia was observed in other MDS-activating lines and treatments. This suggests that MDS gene products contribute to oxygen depletion at the PSI electron-acceptor side. In unstressed growth conditions this MDS-related effect is likely masked by endogenous oxygen evolution and gas exchange with the atmosphere. In rcd1, altered Mehlers reaction coincided with more reduced state of the chloroplast NADPH-thioredoxin oxidoreductase C (NTRC) and its targets, suggesting that NTRC performs feedback control of photosynthesis. This regulation may represent a novel mechanism whereby mitochondrial retrograde signalling affects chloroplast functions.

plant biology↗

bioRxiv2018

Methyl viologen can affect mitochondrial function in Arabidopsis.

Reactive oxygen species (ROS) are key signalling intermediates in plant metabolism, defence, and stress adaptation. The chloroplast and mitochondria are centres of metabolic control and ROS production, which coordinate stress responses in other cell compartments. The herbicide and experimental tool, methyl viologen (MV) induces ROS generation in the chloroplast under illumination, but is also toxic in non-photosynthetic organisms. We used MV to probe plant ROS signalling in compartments other than the chloroplast. Taking a genetic approach in Arabidopsis thaliana, we used natural variation, QTL mapping, and mutant studies with MV in the light, but also under dark conditions, when the chloroplast electron transport is inactive. These studies revealed a light-independent MV-induced ROS-signalling pathway, suggesting mitochondrial involvement. Mitochondrial Mn SUPEROXIDE DISMUTASE was required for ROS-tolerance and the effect of MV was enhanced by exogenous sugar, providing further evidence for the role of mitochondria. Mutant and hormone feeding assays revealed roles for stress hormones in organellar ROS-responses. The radical-induced cell death1 mutant, which is tolerant to MV-induced ROS and exhibits altered mitochondrial signalling, was used to probe interactions between organelles. Our studies implicate mitochondria in the response to ROS induced by MV.

plant biology↗

bioRxiv2018

RCD1 Coordinates Chloroplastic and Mitochondrial Electron Transfer through Interaction with ANAC Transcription Factors

Signaling from chloroplasts and mitochondria, both dependent on reactive oxygen species (ROS), merge at the nuclear protein RADICAL-INDUCED CELL DEATH1 (RCD1). ROS produced in the chloroplasts affect the abundance, thiol redox state and oligomerization of RCD1. RCD1 directly interacts in vivo with ANAC013 and ANAC017 transcription factors, which are the mediators of the ROS-related mitochondrial complex III retrograde signa and suppresses activity of ANAC013 and ANAC017. Inactivation of RCD1 leads to increased expression of ANAC013 and ANAC017-regulated genes belonging to the mitochondrial dysfunction stimulon (MDS), including genes for mitochondrial alternative oxidases (AOXs). Accumulating AOXs and other MDS gene products alter electron transfer pathways in the chloroplasts, leading to diminished production of chloroplastic ROS and increased protection of photosynthetic apparatus from ROS damage. RCD1-dependent regulation affects chloroplastic and mitochondrial retrograde signaling including chloroplast signaling by 3-phosphoadenosine 5-phosphate (PAP). Sensitivity of RCD1 to organellar ROS provides feedback control of nuclear gene expression.

plant biology↗