Maria Duszyn

Background: Ribosomal RNA (rRNA) modifications contribute to ribosome structure and function, yet their distribution and roles in chloroplast ribosomes remain poorly defined. Previous studies have focused on individual enzymes or sites, leaving the global modification landscape and its evolutionary context largely unresolved. Results: Here we present an integrative analysis of post-transcriptional modifications in chloroplast 16 S and 23 S rRNAs of Arabidopsis thaliana . By combining direct RNA sequencing with complementary cDNA-based approaches and meta-analysis of publicly available RNA-seq datasets, we identified seven modified sites in 16 S rRNA and ten in 23 S rRNA with high confidence. Most modifications correspond to conserved bacterial counterparts, indicating that plastid ribosomes retain a prokaryotic-type functional core. In addition, we provide evidence for a methylated cytosine at position C1940 in 23 S rRNA that appears to be conserved within the plant lineage but absent from bacteria, suggesting plastid-specific adaptation. Functional analysis of PFC1, the plastid orthologue of the bacterial dimethyltransferase KsgA, showed that loss of N ⁶, N ⁶-dimethyladenosine formation impairs 16 S rRNA maturation, delays chloroplast ribosome assembly and affects photosynthetic performance in young leaves. Single-molecule DRS analysis of defined 16 S and 23 S rRNA processing states further revealed stage-specific accumulation of modification-associated signatures, consistent with stepwise installation of chloroplast rRNA modifications during ribosome biogenesis. Conclusions: Our results provide a comprehensive and experimentally supported map of chloroplast rRNA modifications and show that plastid rRNA modification is linked to rRNA maturation and ribosome assembly. This work establishes a framework for investigating how conserved and lineage-specific rRNA modifications contribute to plastid ribosome function, chloroplast development and plant responses to environmental conditions.

Lotus corniculatus L. can spontaneously colonize metal-contaminated areas like the old Zn-Pb calamine tailings. This study compared two L. corniculatus ecotypes collected from metal-contaminated (HM) and non-contaminated (NM) sites to identify physiological adaptations to long-term metal exposure. The results indicated that HM ecotype accumulates Zn, Pb, and Cd in shoots without showing any toxic symptoms at the ultrastructural level. The HM ecotype exhibited a different composition of photosynthetic pigments, lower lipid peroxidation, and oxidative stress levels and increased the efficiency of the antioxidant defense system and antioxidant activity compared to the NM ecotype. Leaf antioxidant enzymes such as SOD, CAT, POX, and GPX were more active in the shoots of the HM ecotype, while GR and APX showed lower activity compared to the NM ecotype. In addition, the HM ecotype was characterized by higher glutathione and total phenolics content (mainly catechin, rutin, ferulic, and salicylic acids); however, these non-enzymatic metabolites primarily function in metal chelation alongside their role in oxidative stress mitigation. The results showed that calamine Lotus plants exhibit effective adaptation to long-term metal exposure by keeping metals away from metabolically active compartments and strengthening antioxidant defenses. These coordinated mechanisms reduce oxidative stress and contribute to the enhanced metal tolerance of calamine plants.

Chloroplast development plays a crucial role in plant de-etiolation, a process in which plants switch from growth in darkness to light-driven development, known as photomorphogenesis. This study provides evidence that CIA2 (Chloroplast Import Apparatus 2) and CIL (CIA2-Like) contribute to chloroplast biogenesis, likely by affecting and regulating PSII activity and related gene expression. Although their precise molecular roles remain unclear, our findings support their possible involvement in chloroplast development. This is indicated by downregulation of foliar chlorophyll content, chlorophyll a fluorescence parameters, chloroplast size, and gene expression of PSII molecular markers in the cia2cil double mutant during de-etiolation. Chlorophyll a fluorescence and quantitative gene expression analysis during de-etiolation revealed a significant reduction in PSII maximal efficiency and non-photochemical quenching, as well as deregulated expression of genes such as LHCB2.1 and psbA. According to the immunoblotting and microscopy imaging results, there is an impaired function of PSII and a compromised ultrastructure of the chloroplast membranes in cia2cil plants. However, in CIA2p::CIA2_cia2cil and 35Sp::CIA2_cia2cil complementation lines, reversion of this phenotype was observed. These results suggest a supporting role for CIA2 and CIL in the plant de-etiolation process, expanding our understanding of chloroplast biogenesis regulation.

CYSTEINE-RICH RECEPTOR-LIKE KINASE 5 (CRK5) is a membrane-localized signaling protein implicated in developmental and stress-responsive pathways. Its promoter contains multiple W-box motifs, suggesting regulation by WRKY transcription factors and a potential role in salicylic acid (SA)-dependent signaling. Since SA simultaneously promotes dark-induced senescence and modulates photo-protective dissipation of absorbed energy in excess (AEE) as heat through its effects on non-photochemical quenching (NPQ), stomatal behavior, and leaf temperature, how these SA-driven processes are coordinated remains unclear. Here, we address the unresolved question of whether CRK5 links SA-signaling to the regulation of both senescence and the dissipation of AEE as heat. We demonstrated that loss of CRK5 function leads to increased SA-accumulation, accelerated dark-induced senescence, reduced NPQ, lower foliar temperature, and impaired photosynthetic performance in Arabidopsis (Arabidopsis thaliana). Transcriptomic analysis revealed extensive deregulation of senescence-associated, SA-responsive, and WRKY genes in crk5, particularly under extended darkness. Crucially, introduction of SA-induction-deficient-2 (sid2) or transgenic line (NahG) into the crk5 background fully reverted these phenotypes, whereas disruption of ethylene signaling, ethylene-insensitive-2 (ein2), did not, demonstrating that CRK5 acts specifically through SA-dependent pathways. A line with constitutively enhanced SA levels, constitutive expressor of PR genes 1 (cpr1), showed similar phenotypes to crk5, and exogenous SA further reduced NPQ and leaf temperature across genotypes, confirming that SA negatively regulates foliar AEE dissipation as heat and photosynthetic efficiency. Together, our results identify CRK5 as a key negative regulator of the SA-signaling pathway, which delays dark-induced senescence while positively regulating photosynthesis, NPQ, and thermal dissipation of AEE as heat. This work reveals a previously unrecognized role of CRK5 in coordinating SA-mediated senescence and photo-protective energy management.

Global warming is increasingly constraining plant productivity by altering the photosynthetic energy balance and leaf thermoregulation. Under high light and elevated temperatures, absorption of energy in excess (AEE) by photosystem II disrupts photosynthetic electron transport, oxygen evolution, and CO₂ assimilation, often accompanied by reduced foliar transpiration. These conditions promote photoinhibition, as reflected by a decrease in maximal photosynthetic efficiency (Fv/Fm), an increase in non-photochemical quenching (NPQ), and photooxidative stress associated with enhanced reactive oxygen species (ROS) production. In addition to environmental heat stress, AEE influences foliar temperature through internal energy partitioning, including regulated dissipation of AEE as heat and changes in transpirational cooling. The relative contributions of NPQ, photochemistry, and transpiration to leaf temperature regulation are strongly context dependent and vary with light intensity, temperature changes, and water availability. Under global warming, rising background temperatures and increased vapor pressure deficit may constrain transpirational cooling and alter the balance between non-photochemical and photochemical energy dissipation and usage, respectively. In this review, we synthesize current knowledge on AEE handling, photoinhibition, NPQ and other quenching processes, and on transpiration cooling, and discuss a conceptual framework in which sustained imbalance among these processes under global warming conditions could amplify foliar heat stress and increase the risk of cellular damage. Rather than proposing new physiological mechanisms, this work integrates existing evidence across molecular, leaf, and ecosystem scales to highlight potential feedbacks relevant to plant performance under future climate prediction scenarios.

Improving rye (Secale cereale) yield under increasing climatic stress remains a major challenge for sustainable cereal production. We examined whether early-vegetative physiological, biochemical, and molecular traits can predict final grain yield in hybrid-breeding components. Across three consecutive seasons, 14 genotypes were evaluated under controlled cold-greenhouse conditions for chlorophyll fluorescence, pigment content, hydrogen peroxide (H₂O₂), salicylic acid (SA) levels, and the expression of selected antioxidant and defence-related genes, and these traits were related to yield components. Across years, photosynthetic efficiency (F_v/F_m, Rfd), chlorophyll content, and foliar H₂O₂ emerged as the most consistent predictors of kernel mass, spike number, and kernel number. In contrast, non-photochemical quenching, SA, and carotenoid contents showed weak or inconsistent relationships with yield. These findings indicate that light-harvesting capacity, PSII performance, and oxidative balance are central to reproductive success in rye. The stability of these trait–yield correlations across three seasons provides the basis for a physiological robustness index for hybrid rye, with predictive models achieving accuracies up to R = 0.51. This work demonstrates the potential of using a compact set of early-stage, high-throughput physiological traits to accelerate selection for stress-resilient, high-yielding rye cultivars.

Phytohormones play a key role in regulating every life process of the plant, at every stage of ontogeny

Herbs are valued for their antioxidant richness and traditional use in cuisine and medicine. This study analysed wild herbs (e.g., Achillea, Lamium) and cultivated spices (Salvia, Artemisia) for their bioactive compounds. It was found that antioxidant profiles varied notably among species, even within the same family. Helichrysum italicum and Salvia officinalis had the highest polyphenol levels, while Achillea millefolium and Ocimum basilicum had the lowest. Total polyphenols did not always correlate with antioxidant activity. For instance, Petroselinum hortense and Salvia rosmarinus showed high antioxidant activity despite low polyphenol levels, whereas Levisticum officinale and Artemisia dracunculus combined both. Mentha spicata, M. x citrata, Origanum vulgare, and S. officinalis were rich in carotenoids, while H. italicum showed high α-carotene but low levels of other carotenoids. Most Lamiaceae accumulated a high amount of chlorophylls and polyphenols. Cultivated herbs like M. spicata, M. x citrata, and S. officinalis exhibited stronger and more diverse properties than wild species. It can be concluded that taxonomy alone does not predict antioxidant potential. The differences observed may be attributed to species-specific metabolic pathways, ecological adaptations, or environmental factors influencing phytochemical expression. These findings highlight the importance of conducting species-level screenings in the search for plant-derived antioxidants with potential therapeutic applications.

Global warming intensifies heat waves and drought, causing energy absorption in excess (EAE) in plants, thereby inhibiting transpiration and photosynthesis. Non-photochemical quenching (NPQ) contributes significantly to EAE dissipation as heat, with leaves emitting ca. 107 W m ^-2 while absorbing ca. 417 W m ^-2 . Foliar temperature is further elevated when transpiration is inhibited, but NPQ is not increased. Surprisingly, during generic photosynthetic electron transport and NPQ partial inhibition, foliar temperature under EAE was reduced considerably. Our findings emphasize the importance of mutual co-regulation of photosynthetic electron transport, NPQ, and transpiration in foliar temperature regulation and suggest that overall heat emission from forest ecosystems may conditionally vary on a terawatt (TW) scale per 1,000,000 km ^-2 . Global warming models do not take into account this putative phenomenon. One Sentence Summary: Photosynthesis and Foliar Thermoregulation

Guanosine 3′,5′-cyclic monophosphate (cGMP) is an important signaling molecule in plants. cGMP and guanylyl cyclases (GCs), enzymes that catalyze the synthesis of cGMP from GTP, are involved in several physiological processes and responses to environmental factors, including pathogen infections. Using in vitro analysis, we demonstrated that recombinant BdGUCD1 is a protein with high guanylyl cyclase activity and lower adenylyl cyclase activity. In Brachypodium distachyon, infection by Fusarium pseudograminearum leads to changes in BdGUCD1 mRNA levels, as well as differences in endogenous cGMP levels. These observed changes may be related to alarm reactions induced by pathogen infection. As fluctuations in stress phytohormones after infection have been previously described, we performed experiments to determine the relationship between cyclic nucleotides and phytohormones. The results revealed that inhibition of cellular cGMP changes disrupts stress phytohormone content and responses to pathogen. The observations made here allow us to conclude that cGMP is an important element involved in the processes triggered as a result of infection and changes in its levels affect jasmonic acid. Therefore, stimuli-induced transient elevation of cGMP in plants may play beneficial roles in priming an optimized response, likely by triggering the mechanisms of feedback control.