Biology subjects

Schuster, G.

Publications and source records attributed to Schuster, G..

9 recordsLinked to original sources

bioRxiv2026

Overexpression of Active or Inactive RNase J Disrupts Chloroplast RNA Quality Control in Arabidopsis

The chloroplast is a semi-autonomous organelle with a compact genome encoding ~100 expressed genes. Numerous and widespread promoters coupled with inefficient transcription termination leads to a highly complex primary transcriptome that undergoes extensive RNA quality control orchestrated by RNA binding proteins and ribonucleases. Among the ribonucleases, only RNase J (RNJ) is absolutely required for plant germination and survival, likely because its deficiency leads to massive accumulation of antisense RNA which inhibits translation. As one approach to understanding the selectivity of RNJ for antisense RNA and noncoding regions, we created Arabidopsis lines overexpressing catalytically inactive versions of the enzyme designed to trap its substrates. Initially, transgenic plants appeared phenotypically normal. However, crosses used to generate homozygous transgenic lines yielded progeny that developed varying degrees of chlorosis within 2-3 weeks. Concomitantly, these plants exhibited chloroplast transcriptome alterations similar to RNJ-silenced lines, along with mRNA changes consistent with retrograde signaling. This chlorosis could be correlated to the likely decay of RNJ protein, but not its endogenous transcript. The result could be replicated by attempting to overexpress a wild-type version of RNJ, in which case even one transgene copy was sufficient to induce chlorosis. Our results suggest that RNJ is under protein expression level surveillance to prevent wholesale destruction of the plastid transcriptome.

plant biology↗

bioRxiv2025

The GT1 domain of RNase J ensures RNA quality control through dsRNA binding in Arabidopsis plastids

RNase J is a ribonuclease found in bacteria, archaea, and plant chloroplasts, and plays diverse roles in RNA maturation and stability. Chloroplast RNase J is encoded by the nuclear RNJ locus and is essential for embryo maturation. Arabidopsis or tobacco plants depleted for RNase J accumulate massive amounts of double-stranded RNA, which interferes with translation and causes chlorosis. Land plant RNase J uniquely contains a C-terminal GT1 domain, a DNA- binding motif found in transcription factors. Here, we have used complementation of an Arabidopsis rnj mutant with versions of RNase J with a mutated or deleted GT1 domain to investigate its role in RNase J function. We show that in vitro, the recombinant GT1 domain binds both double-stranded RNA and DNA, but not single-stranded nucleic acids, with no sequence specificity. Furthermore, while RNase J lacking GT1 binding complements the rnj mutant, these plants accumulate high levels of dsRNA as detected by immunolocalization and RNA-Seq. GT1 mutations also change RNase J solubility in vivo, suggesting that the GT1 domain is involved in localization within the plastid. Taken together, our results suggest that the GT1 domain plays a key role in dsRNA removal through localizing the enzyme and/or selectively binding the dsRNA substrate. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/682605v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@e5642borg.highwire.dtl.DTLVardef@136456org.highwire.dtl.DTLVardef@1205466org.highwire.dtl.DTLVardef@184f72b_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2024

The high-light-tolerant desert alga Chlorella ohadii is protected from oxidative stress by a non-photochemical quenching-independent mechanism

Non-photochemical quenching (NPQ) mechanisms are crucial for protecting photosynthesis from photoinhibition in plants, algae, and cyanobacteria, and their modulation is a long-standing goal for improving photosynthesis and crop yields. The current work demonstrates that Chlorella ohadii, a green micro-alga that thrives in the desert under high light intensities which are fatal to many photosynthetic organisms, does not perform nor require NPQ to protect photosynthesis under constant high light. Instead of dissipating excess energy, it minimizes its uptake by eliminating the photosynthetic antenna of photosystem II. In addition it accumulates antioxidants that neutralize harmful reactive oxygen species (ROS) and ramps up cyclic electron flow around PSI. These NPQ-independent responses proved efficient in preventing ROS accumulation and reducing oxidative damage to proteins in high-light-grown cells.

plant biology↗

bioRxiv2023

The protein phosphorylation landscape in photosystem I of the desert algae Chlorella sp.

O_LIThe phosphorylation of photosystem II (PSII) and its antenna (LHCII) proteins has been extensively studied and its involvement in state transitions and PSII repair is well known. Yet, very little is known about the extent and functions of phosphorylation of photosystem I (PSI) and its antenna (LHCI) proteins. C_LIO_LIHere, two proteomics methods were applied to generate a detailed map of the phosphorylation sites of the PSI-LHCI proteins in Chlorella ohadii cells that were grown under low- or extreme high-light intensities (LL and HL). Furthermore, we analyzed the content of oxidized tryptophans in these cell types to estimate light-induced oxidative damage to PSI-LHCI. C_LIO_LIOur work revealed the phosphorylation of 11 out of 22 PSI-LHCI subunits. The analyses detected extensive phosphorylation of the LHCI subunits lhca6 and lhca7. Other PSI-LHCI subunits were phosphorylated to a lesser extent. Additionally, we show the accumulation of oxidatively damaged tryptophans in the psaD subunit of PSI of HL-grown C. ohadii. C_LIO_LIThe significant phosphorylation of lhca6 and lhca7 suggests a physiological role during photosynthesis, possibly by altering light-harvesting characteristics and binding of other LHCI subunits. Moreover, we show that psaD is susceptible to photodamage while LHCI is protected from ROS under HL. C_LI

plant biology↗

bioRxiv2022

A desert green alga that thrives at extreme high-light intensities using a unique photoin-hibition protection mechanism

While light is the driving force of photosynthesis, excessive light can be harmful. Photoinhibition, or light-induced photo-damage, is one of the key processes limiting photosynthesis. When the absorbed light exceeds the amount that can be dissipated by photosynthetic electron flow and other processes, damaging radicals are formed that mostly inactivate photosystem II (PSII). A well-defined mechanism that protects the photosynthetic apparatus from photoinhibition has been described in the model green alga Chlamydomonas reinhardtii and plants. Chlorella oha-dii is a green micro-alga, isolated from biological desert soil crusts, that thrives under extreme high light (HL) in which other organisms do not survive. Here, we show that this alga evolved unique protection mechanisms distinct from those of C. reinhardtii and plants. When grown under extreme HL, significant structural changes were noted in the C. ohadii thylakoids, including a drastic reduction in the antennae and the formation of stripped core PSII, lacking its outer and inner antennae. This is accompanied by a massive accumulation of protective carotenoids and proteins that scavenge harmful radicals. At the same time, several elements central to photoinhibition protection in C. reinhardtii, such as psbS, the stress-related light harvesting complex, PSII protein phosphorylation and state-transitions are entirely absent or were barely detected in C. ohadii. Taken together, a unique photoinhibition protection mechanism evolved in C. ohadii, enabling the species to thrive under extreme-light intensities where other photo-synthetic organisms fail to survive.

plant biology↗

bioRxiv2022

Trichodesmium Erythraeum produces a higher photocurrent than other cyanobacterial species in bio-photo electrochemical cells.

In recent years, the increase in world energy consumption, and the worries from potential future disasters that may derive from climate change have inspired the motivation to develop renewable energy technologies. One of the promising methods is the utilization of whole bacterial cells to produce photocurrent in a bio-photo electrochemical cell (BPEC). The photocurrent derives from the photosynthesis pathway, while the redox couple NADP+/NADPH perform cyclic electron mediation between photosystem I inside the cells, and the anode. Over the years, various cyanobacterial species were utilized in diverse BPECs setups, while the photocurrent was enhanced by the addition of natural electron mediators such as NAD+, NADP+, Cytochrome C, Vitamin B1, and the artificial mediator potassium ferricyanide. The cyanobacterium Trichodesmium Erythraeum (Te) is a marine species that consist of high content of Phycocyanin and Phycoerythrin pigments that play a major role in photosynthesis enhancement. In this work, we produce for the first-time photocurrent from Te. We apply 2D-fluorescence measurements to detect its NADPH secretion and show that its photocurrent production is enhanced as a function of increasing electrolyte salinity. Finally, we produce photocurrent from additional cyanobacterial species: Synechocystis sp. PCC6803, Synechococcus elongatus PCC 7942, Acaryochloris marina MBIC 11017, and Spirulina, using their cultivation medium as electrolytes in the BPEC. We show that TE produces a photocurrent intensity that is significantly greater than all other species with and without the addition of exogenous electron mediators. The utilization of TE may pave the way toward the establishment of marine clean energy technologies.

microbiology↗

bioRxiv2021

Harvesting electrical current from intact plant leaves

Here, we show that it is possible to harvest photocurrent directly from unprocessed plant tissues from terrestrial or aquatic environments in bio-photoelectrochemical cells (BPECs) and use the current to produce molecular H2. The source of electrons is shown to originate from the Photosystem II water-oxidation reaction and utilizes exported mediating molecules, especially NADPH. The photocurrent production is dependent on the concentration of the photosynthetic complexes, as an increase in total chlorophyll and oxygen evolution rates lead to increased photocurrent rates. The permeability of the outer leaf surface is another important factor in photocurrent harvesting. Different tissues produce photocurrent densities in the range of [~] 1 - 10 mA / cm2 which is significantly higher than microorganism-based BPECs. The relatively high photocurrent and the simplicity of the plants BPEC may pave the way toward the development of future applicative photosynthetic based energy technologies.

bioengineering↗

bioRxiv2021

Bioelectricity generation from live marine photosynthetic macroalgae

Conversion of solar energy into electrical current by photosynthetic organisms has the potential to produce clean energy. Previously reported bio-photoelectrochemical cells (BPECs) have utilized unicellular photosynthetic microorganisms. In this study, we describe for the first time BPECs that utilize intact live marine macroalgae (seaweeds) in natural seawater or saline buffer or natural seawater. The BPECs produce electrical currents from of >50mA/cm2, from both light-dependent (photosynthesis) and light independent processes. These values are significantly greater than the current densities that have been reported for single-cell microorganisms. The photocurrent is inhibited by the Photosystem II inhibitor DCMU, indicating that the source of light-driven electrons is from water oxidation via NADPH and other reduced molecules. We show here that intact seaweed cultures can be used in a large-scale BPEC containing seawater that produces bias-free photocurrent. The ability to produce bioelectricity from intact seaweeds may pave the way to future development of a low-cost energy technology using BPECs.

bioengineering↗

bioRxiv2021

The desert green algae Chlorella ohadii thrives at excessive high light intensities by exceptionally enhancing the mechanisms that protect photosynthesis from photoinhibition

Although light is the driving force of photosynthesis, excessive light can be harmful. One of the main processes that limits photosynthesis is photoinhibition, the process of light-induced photodamage. When the absorbed light exceeds the amount that is dissipated by photosynthetic electron flow and other processes, damaging radicals are formed that mostly inactivate photosystem II (PSII). Damaged PSII must be replaced by a newly repaired complex in order to preserve full photosynthetic activity. Chlorella ohadii is a green micro-alga, isolated from biological desert soil crusts, that thrives under extreme high light and is highly resistant to photoinhibition. Therefore, C. ohadii is an ideal model for studying the molecular mechanisms underlying protection against photoinhibition. Comparison of the thylakoids of C. ohadii cells that were grown under low light versus extreme high light intensities, found that the alga employs all three known photoinhibition protection mechanisms: i) massive reduction of the PSII antenna size; ii) accumulation of protective carotenoids; and iii) very rapid repair of photo-damaged reaction center proteins. This work elucidated the molecular mechanisms of photoinhibition resistance in one of the most light-tolerant photosynthetic organisms and shows how photoinhibition protection mechanisms evolved to marginal conditions, enabling photosynthesis-dependent life in severe habitats. One Sentence HighlightAnalysis of the photosynthetic properties of a desert algae that thrives at extreme high light intensities revealed protection from photoinhibition driven by the remarkable enhancement of three protection mechanisms.

plant biology↗