In plant cells, plastids form elongated extensions called stromules, the regulation and purposes of which remain unclear. Here, we quantitatively explore how different stromule structures serve to enhance the ability of a plastid to interact with other organelles: increasing the effective space for interaction and biomolecular exchange between organelles. Interestingly, electron microscopy and confocal imaging showed that the cytoplasm in Arabidopsis thaliana and Nicotiana benthamiana epidermal cells is extremely thin (around 100 nm in regions without organelles), meaning that inter-organelle interactions effectively take place in 2D. We combine these imaging modalities with mathematical modeling and new in planta experiments to demonstrate how different stromule varieties (single or multiple, linear or branching) could be employed to optimize different aspects of inter-organelle interaction capacity in this 2D space. We found that stromule formation and branching provide a proportionally higher benefit to interaction capacity in 2D than in 3D. Additionally, this benefit depends on optimal plastid spacing. We hypothesize that cells can promote the formation of different stromule architectures in the quasi-2D cytoplasm to optimize their interaction interface to meet specific requirements. These results provide new insight into the mechanisms underlying the transition from low to high stromule numbers, the consequences for interaction with smaller organelles, how plastid access and plastid to nucleus signaling are balanced and the impact of plastid density on organelle interaction.

Hypoxia in tumors contributes to chemotherapy resistance, worsened by acidosis driven by carbonic anhydrases (hCA IX and XII). Targeting these enzymes can mitigate acidosis, thus enhancing tumor sensitivity to cytotoxic drugs. Herein, novel 4-(pyrazolyl)benzenesulfonamide ureas (SH7a−t) were developed and evaluated for their inhibitory activity against hCA IX and XII. They showed promising results (hCA IX: KI =15.9−67.6 nM, hCA XII: KI = 16.7−65.7 nM). Particularly, SH7s demonstrated outstanding activity (KIs = 15.9 nM for hCA IX and 55.2 nM for hCA XII) and minimal off-target kinase inhibition over a panel of 258 kinases. In NCI anticancer screening, SH7s exhibited broad-spectrum activity with an effective growth inhibition full panel GI50 (MG-MID) value of 3.5 μM and a subpanel GI50 (MG-MID) range of 2.4−6.3 μM. Furthermore, SH7s enhanced the efficacy of Taxol and 5-fluorouracil in cotreatment regimens under hypoxic conditions in HCT-116 colorectal cancer cells, indicating its potential as a promising anticancer agent.

Plant cell walls are sophisticated carbohydrate-rich structures representing the immediate contact surface with the extracellular environment, often serving as the first barrier against biotic and abiotic stresses. Notably, a variety of perturbations in plant cell walls result in upregulated jasmonate (JA) production, a phytohormone with essential roles in defense and growth responses. Hence, cell wall-derived signals can initiate intracellular JA-mediated responses and the elucidation of the underlying signaling pathways could provide novel insights into cell wall maintenance and remodeling, as well as advance our understanding on how is JA biosynthesis initiated. This Mini Review will describe current knowledge about cell wall-derived damage signals and their effects on JA biosynthesis, as well as provide future perspectives.

Recognition of pathogen-associated molecular patterns (PAMPs) induces multiple defense mechanisms to limit pathogen growth. Here, we show that the Arabidopsis thaliana tandem zinc finger protein 9 (TZF9) is phosphorylated by PAMP-responsive mitogen-activated protein kinases (MAPKs) and is required to trigger a full PAMP-triggered immune response. Analysis of a tzf9 mutant revealed attenuation in specific PAMP-triggered reactions such as reactive oxygen species accumulation, MAPK activation and, partially, the expression of several PAMP-responsive genes. In accordance with these weaker PAMP-triggered responses, tzf9 mutant plants exhibit enhanced susceptibility to virulent Pseudomonas syringae pv. tomato DC3000. Visualization of TZF9 localization by fusion to green fluorescent protein revealed cytoplasmic foci that co-localize with marker proteins of processing bodies (P-bodies). This localization pattern is affected by inhibitor treatments that limit mRNA availability (such as cycloheximide or actinomycin D) or block nuclear export (leptomycin B). Coupled with its ability to bind the ribohomopolymers poly(rU) and poly(rG), these results suggest involvement of TZF9 in post-transcriptional regulation, such as mRNA processing or storage pathways, to regulate plant innate immunity.

Nicotiana tabacum (tobacco) plants have short and long glandular trichomes. There is evidence that tobacco trichomes play several roles in the defense against biotic and abiotic stresses. cDNA libraries were constructed from control and cadmium (Cd)-treated leaf trichomes. Almost 2,000 expressed sequence tag (EST) cDNA clones were sequenced to analyze gene expression in control and Cd-treated leaf trichomes. Genes for stress response as well as for primary metabolism scored highly, indicating that the trichome is a biologically active and stress-responsive tissue. Reverse transcription–PCR (RT–PCR) analysis demonstrated that antipathogenic T-phylloplanin-like proteins, glutathione peroxidase and several classes of pathogenesis-related (PR) proteins were expressed specifically or dominantly in trichomes. Cysteine-rich PR proteins, such as non-specific lipid transfer proteins (nsLTPs) and metallocarboxypeptidase inhibitors, are candidates for the sequestration of metals. The expression of osmotin and thaumatin-like proteins was induced by Cd treatment in both leaves and trichomes. Confocal laser scanning microscopy (CLSM) showed that glutathione levels in tip cells of both long and short trichomes were higher than those in other types of leaf cells, indicating the presence of an active sulfur-dependent protective system in trichomes. Our results revealed that the trichome-specific transcriptome approach is a powerful tool to investigate the defensive functions of trichomes against both abiotic and biotic stress. Trichomes are shown to be an enriched source of useful genes for molecular breeding towards stress-tolerant plants.

Many tumor cells exhibit a disturbed intracellular redox state resulting in higher levels of reactive oxygen species (ROS). As these contribute to tumor initiation and sustenance, catalytic redox agents combining significant activity with substrate specificity promise high activity and selectivity against oxidatively stressed malignant cells. We describe here the design and synthesis of novel organochalcogen based redox sensor/effector catalysts. Their selective anticancer activity at submicromolar and low micromolar concentrations was established here in a range of tumor entities in various biological systems including cell lines, primary tumor cell cultures, and animal models. In the B-cell derived chronic lymphocytic leukemia (CLL), for instance, such compounds preferentially induce apoptosis in the cancer cells while peripheral blood mononuclear cells (PBMC) from healthy donors and the subset of normal B-cells remain largely unaffected. In support of the concept of sensor/effector based ROS amplification, we are able to demonstrate that underlying this selective activity against CLL cells are pre-existing elevated ROS levels in the leukemic cells compared to their nonmalignant counterparts. Furthermore, the catalysts act in concert with certain chemotherapeutic drugs in several carcinoma cell lines to decrease cell proliferation while showing no such interactions in normal cells. Overall, the high efficacy and selectivity of (redox) catalytic sensor/effector compounds warrant further, extensive testing toward transfer into the clinical arena.

The induced defense response in plants towards herbivores is mainly regulated by jasmonates and leads to the accumulation of so-called jasmonate-induced proteins. Recently, a jasmonate (JA) inducible lectin called Nicotiana tabacum agglutinin or NICTABA was discovered in tobacco (N. tabacum cv Samsun) leaves. Tobacco plants also accumulate the lectin after insect attack by caterpillars. To study the functional role of NICTABA, the accumulation of the JA precursor 12-oxophytodienoic acid (OPDA), JA as well as different JA metabolites were analyzed in tobacco leaves after herbivory by larvae of the cotton leafworm (Spodoptera littoralis) and correlated with NICTABA accumulation. It was shown that OPDA, JA as well as its methyl ester can trigger NICTABA accumulation. However, hydroxylation of JA and its subsequent sulfation and glucosylation results in inactive compounds that have lost the capacity to induce NICTABA gene expression. The expression profile of NICTABA after caterpillar feeding was recorded in local as well as in systemic leaves, and compared to the expression of several genes encoding defense proteins, and genes encoding a tobacco systemin and the allene oxide cyclase, an enzyme in JA biosynthesis. Furthermore, the accumulation of NICTABA was quanti-fied after S. littoralis herbivory and immunofluorescence microscopy was used to study the localization of NICTABA in the tobacco leaf.

The inhibition of human glutaminyl cyclase (hQC) has come into focus as a new potential approach for the treatment of Alzheimer’s disease. The hallmark of this principle is the prevention of the formation of Aβ3,11(pE)-40,42, as these Aβ-species were shown to be of elevated neurotoxicity and likely to act as a seeding core leading to an accelerated formation of Aβ-oligomers and fibrils. Starting from 1-(3-(1H-imidazol-1-yl)propyl)-3-(3,4-dimethoxyphenyl)thiourea, bioisosteric replacements led to the development of new classes of inhibitors. The optimization of the metal-binding group was achieved by homology modeling and afforded a first insight into the probable binding mode of the inhibitors in the hQC active site. The efficacy assessment of the hQC inhibitors was performed in cell culture, directly monitoring the inhibition of Aβ3,11(pE)-40,42 formation.

Previous experiments with tobacco (Nicotiana tabacum L. cv Samsun NN) plants revealed that jasmonic acid methyl ester (JAME) induces the expression of a cytoplasmic/nuclear lectin in leaf cells and provided the first evidence that jasmonates affect the expression of carbohydrate-binding proteins in plant cells. To corroborate the induced accumulation of relatively large amounts of a cytoplasmic/nuclear lectin, a detailed study was performed on the induction of the lectin in both intact tobacco plants and excised leaves. Experiments with different stress factors demonstrated that the lectin is exclusively induced by exogeneously applied jasmonic acid and JAME, and to a lesser extent by insect herbivory. The lectin concentration depends on leaf age and the position of the tissue in the leaf. JAME acts systemically in intact plants but very locally in excised leaves. Kinetic analyses indicated that the lectin is synthesized within 12 h exposure time to JAME, reaching a maximum after 60 h. After removal of JAME, the lectin progressively disappears from the leaf tissue. The JAME-induced accumulation of an abundant nuclear/cytoplasmic lectin is discussed in view of the possible role of this lectin in the plant.

Tyrosine phosphorylation represents a unique signaling process that controls metabolic pathways, cell activation, growth and differentiation, membrane transport, apoptosis, neural, and other functions. We present here the three-dimensional structure of Fyn tyrosine kinase, a Src-family enzyme involved in T-cell receptor signal transduction. The structure of Fyn was modeled for homology using the Sybyl-Composer suite of programs for modeling. Procheck and Prosa II programs showed the high quality of the obtained three-dimensional model. Rosmarinic acid, a secondary metabolite of herbal plants, was discovered as a new Fyn kinase inhibitor using immunochemical and in silico methods. Two possible binding modes of rosmarinic acid were evaluated here, i.e., near to or in the ATP-binding site of kinase domain of Fyn. Enzyme kinetic experiments revealed that Fyn is inhibited by a linear-mixed noncompetitive mechanism of inhibition by rosmarinic acid. This indicates that rosmarinic acid binds to the second “non-ATP” binding site of the Fyn tyrosine kinase.