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Reactive oxygen species (ROS) are signaling molecules essential for plant responses to abiotic and biotic stimuli as well as for multiple developmental processes. They are produced as byproducts of aerobic metabolism and are affected by adverse environmental conditions. The ROS content is controlled on the side of their production but also by scavenging machinery. Antioxidant enzymes represent a major ROS-scavenging force and are crucial for stress tolerance in plants. Enzymatic antioxidant defense occurs as a series of redox reactions for ROS elimination. Therefore, the deregulation of the antioxidant machinery may lead to the overaccumulation of ROS in plants, with negative consequences both in terms of plant development and resistance to environmental challenges. The transcriptional activation of antioxidant enzymes accompanies the long-term exposure of plants to unfavorable environmental conditions. Fast ROS production requires the immediate mobilization of the antioxidant defense system, which may occur via retrograde signaling, redox-based modifications, and the phosphorylation of ROS detoxifying enzymes. This review aimed to summarize the current knowledge on signaling processes regulating the enzymatic antioxidant capacity of plants.

Iron superoxide dismutase 1 (FSD1) was recently characterized as a plastidial, cytoplasmic, and nuclear enzyme with osmoprotective and antioxidant functions. However, the current knowledge on its role in oxidative stress tolerance is ambiguous. Here, we characterized the role of FSD1 in response to methyl viologen (MV)-induced oxidative stress in Arabidopsis thaliana . In accordance with the known regulation of FSD1 expression, abundance, and activity, the findings demonstrated that the antioxidant function of FSD1 depends on the availability of Cu 2+ in growth media. Arabidopsis fsd1 mutants showed lower capacity to decompose superoxide at low Cu 2+ concentrations in the medium. Prolonged exposure to MV led to reduced ascorbate levels and higher protein carbonylation in fsd1 mutants and transgenic plants lacking a plastid FSD1 pool as compared to the wild type. MV induced a rapid increase in FSD1 activity, followed by a decrease after 4 h long exposure. Genetic disruption of FSD1 negatively affected the hydrogen peroxide-decomposing ascorbate peroxidase in fsd1 mutants. Chloroplastic localization of FSD1 is crucial to maintain redox homeostasis. Proteomic analysis showed that the sensitivity of fsd1 mutants to MV coincided with decreased abundances of ferredoxin and photosystem II light-harvesting complex proteins. These mutants have higher levels of chloroplastic proteases indicating an altered protein turnover in chloroplasts. Moreover, FSD1 disruption affects the abundance of proteins involved in the defense response. Collectively, the study provides evidence for the conditional antioxidative function of FSD1 and its possible role in signaling.

The forest canopy, as a biodiversity hotspot with many wildlife habitats, remains a difficult site to access for researchers and forest managers. Here, we present a novel, small, unmanned aerial vehicle, called the Druid Drone (DD), equipped with a multifunctional manipulator designed for tree crown management and biodiversity research. Its use is demonstrated by studies and the control of the widespread, obligatory hemiparasitic European mistletoe (Viscum album L.). The DD provides integrated pest management by canopy surveying, spraying and sampling of leaves/branches for further studies. The pilot and operator, using first person view goggles, handle the lightweight backpack‐sized drone (DJI Mavic 2 Pro, Air 2, Phantom 3 or custom Rotorama quadcopter) equipped with a manipulator and five replaceable 3D‐printed functional modules. These include the peripheral high‐resolution Observer camera for close, non‐invasive inspection of tree crowns, the entomological Collector unit for arthropod trapping, the forceps arm Sampler for soft plant tissue collection, the terminal Secator saw for cutting harder tree tissues such as twigs and the Green Doctor precision sprayer, which disperses growth regulators or other compounds for targeted tree and mistletoe management. This method offers a potential solution for safe, precise and minimally invasive research on forest canopy biodiversity in different forest types across the globe, tree health care and mistletoe management as compared to the manual work of arborists or the use of canopy cranes, forest helicopters and firearms. Анотація Крони дерев відомі значним біорізноманіттям та численими екологічними нішами для багатьох форм життя, проте вони досі залишаються складнодосяжними для дослідників та менеджерів лісу. У цій публікації йдеться про Druid Drone (DD)—новий компактний безпілотний літальний апарат (БЛА), оснащений мультифункціональним маніпулятором для впорядкування крон дерев та вивчення їх біорізноманіття. Перспективність застосування DD було доведено на прикладі дослідження та контролю відомої повсюдної напівпаразитичної рослини омели білої (Viscum album L.). DD забезпечує реалізацію комплексної стратегії контролю омели, що досягається шляхом огляду крони дерев, оприскування регуляторами росту та відбором зразків листків і/або гілок для подальших досліджень. Пілот та оператор, використовуючи FPV‐окуляри (від англ. First Person View—вид від першої особи), узгоджено керують польотом та маніпуляціями легкого компактного дрона (DJI Mavic 2 Pro, Air 2, Phantom 3, або самотужки зібраного квадрокоптера фірми Rotorama), до якого приєднано маніпулятор з п'ятьма змінними функціональними модулями, надрукованими на 3D‐принтері. До складу набору входить модуль Observer (Спостерігач)—периферійна камера з високою роздільною здатністю для неінвазійного обстеження крон дерев із близьких відстаней; ентомологічний модуль Collector (Ловець) для полювання на безхребетних; лапка‐пінцет Sampler (Збирач) для делікатного відбору зразків м'яких тканин; гостра пилка Secator (Обтинач) для збирання твердіших зразків, наприклад, гілок; та прицільний оприскувач Green Doctor (Зелений Лікар) для нанесення регуляторів росту або інших сполук для контролю здоров'я дерев та поширення омели. Цей метод є зручним рішенням для безпечного, прицільного та щадного дослідження біорізноманіття крон дерев у різних типах лісів числених екосистем світу, а також для контролю стану дерев у порівнянні з ручною працею арбористів та використанням пересувних платформ, гелікоптерів або вогнепальної зброї.

Strigolactones are plant hormones regulating cytoskeleton-mediated developmental events in roots, such as lateral root formation and elongation of root hairs and hypocotyls. The latter process was addressed herein by the exogenous application of a synthetic strigolactone, GR24, and an inhibitor of strigolactone biosynthesis, TIS108, on hypocotyls of wild-type Arabidopsis and a strigolactone signaling mutant max2-1 (more axillary growth 2-1) . Owing to the interdependence between light and strigolactone signaling, the present work was extended to seedlings grown under a standard light/dark regime, or under continuous darkness. Given the essential role of the cortical microtubules in cell elongation, their organization and dynamics were characterized under the conditions of altered strigolactone signaling using fluorescence microscopy methods with different spatiotemporal capacities, such as confocal laser scanning microscopy (CLSM) and structured illumination microscopy (SIM). It was found that GR24-dependent inhibition of hypocotyl elongation correlated with changes in cortical microtubule organization and dynamics, observed in living wild-type and max2-1 seedlings stably expressing genetically encoded fluorescent molecular markers for microtubules. Quantitative assessment of microscopic datasets revealed that chemical and/or genetic manipulation of strigolactone signaling affected microtubule remodeling, especially under light conditions. The application of GR24 in dark conditions partially alleviated cytoskeletal rearrangement, suggesting a new mechanistic connection between cytoskeletal behavior and the light-dependence of strigolactone signaling.

Although cytoskeleton is a driving force for cell division and growth in higher plants, there is little evidence about its components in parasitic angiosperms. Microtubules and actin filaments in cells of shoot apical meristem and root-like structure of stem holoparasites European ( L.) and Eastern ( a Vahl.) dodders, as well as in prehaustorium, the specific organ adapted to parasitism, were visualized for the first time by immunolabeling and fluorescence microscopy. The significance of cytoskeletal elements during germination and prehaustorium formation was addressed by treatments with taxol, oryzalin, latrunculin B, cytochalasin B/D, jasplakinolide, and 2,3-butanedione monoxime. In shoot apical meristem many dividing cells were observed, in contrast to root-like structure, devoid of cell divisions. Cortical microtubules were oriented transversely and/or obliquely, while actin filaments were randomly distributed in cells of both organs. Furthermore, longitudinal cortical microtubules were present in digitate cells of prehaustorium, and transverse arrays were found in its file cells. Long and short random actin filaments were also observed in prehaustorium cells. Thus, it was shown that the cytoskeleton in dodder shoot cells is organized in a similar way to non-parasitic dicots, while cytoskeletal organization has some peculiarities in quickly senescing root-like structure and prehaustorium.

During last years, selective tyrosine nitration of plant proteins gains importance as well-recognized pathway of direct nitric oxide (NO) signal transduction. Plant microtubules are one of the intracellular signaling targets for NO, however, the molecular mechanisms of NO signal transduction with the involvement of cytoskeletal proteins remain to be elucidated. Since biochemical evidence of plant α-tubulin tyrosine nitration has been obtained recently, potential role of this posttranslational modification in regulation of microtubules organization in plant cell is estimated in current paper. It was shown that 3-nitrotyrosine (3-NO2-Tyr) induced partially reversible Arabidopsis primary root growth inhibition, alterations of root hairs morphology and organization of microtubules in root cells. It was also revealed that 3-NO2-Tyr intensively decorates such highly dynamic microtubular arrays as preprophase bands, mitotic spindles and phragmoplasts of Nicotiana tabacum Bright Yellow-2 (BY-2) cells under physiological conditions. Moreover, 3D models of the mitotic kinesin-8 complexes with the tail of detyrosinated, tyrosinated and tyrosine nitrated α-tubulin (on C-terminal Tyr 450 residue) from Arabidopsis were reconstructed in silico to investigate the potential influence of tubulin nitrotyrosination on the molecular dynamics of α-tubulin and kinesin-8 interaction. Generally, presented data suggest that plant α-tubulin tyrosine nitration can be considered as its common posttranslational modification, the direct mechanism of NO signal transduction with the participation of microtubules under physiological conditions and one of the hallmarks of the increased microtubule dynamics.

The obligate root parasite Cistanche armena is a recently rediscovered, extremely rare endangered species endemic to Armenia, specifically parasitizing camelthorn ( Alhagi maurorum , Fabaceae) and saltwort ( Salsola dendroides , Chenopodiaceae). Its populations are reputedly declining due to habitat destruction and biotic impacts. Since the only known means of its reproduction is via the seeds, understanding the mechanisms of breaking C. armena seed dormancy and germination along with the related aspects of the species’ biology is highly important both from fundamental (functional ecology and evolution) and applied (conservation and management) perspectives. Here, we present the first in vitro seed germination protocol for C. armena involving fluridone, a systemic herbicide targeting the carotenoid biosynthetic pathway. In addition, the seed micromorphology of C. armena is described using both light microscopy and lignin autofluorescence visualized by confocal laser scanning microscopy. The actin cytoskeleton in radicle cells of germinated C. armena seedlings is described for the first time, being the proof of seed viability. Further elaboration and application of the proposed germination protocol with the cultivation of C. armena on susceptible hosts are altogether seen as a valuable tool for the conservation of this species.

Juniperus excelsa s. str. (Greek juniper) in Crimea is a relic species on the limits of its range, and represents the Mediterranean flora in the Sub-Mediterranean part of the peninsula. Its origin and history in this area remains unresolved. We aimed to analyze phylogeny and potential demographic expansion of the juniper in the Crimea as well as to study its morphological differentiation. We analyzed plant material from 59 trees inhabiting eight populations. Genetic variation assessments were based on the four non-coding chloroplast DNA (cpDNA) fragments and the nuclear internal transcribed spacer region ITS1-5,8S-ITS2 (ITS). To examine the morphological differentiation, eight measured/counted traits of cones, seeds, and shoots were chosen and eight ratios were calculated. Morphological parameters were compared using ANOVA, Student’s t test, discrimination analysis and Kruskal-Wallis and U Mann-Whitney tests. Two cpDNA fragments were polymorphic and, in total, 10 cpDNA haplotypes were found. Haplotype diversity (Hd) ranged from 0.0 to 0.9. Based on both cpDNA and ITS sequences variation, phylogenetic analyses revealed a close relationship of the Crimean junipers to the individuals from other parts of the species range. In general, our molecular results confirmed the low level of genetic differentiation of J. excelsa individuals inhabiting different parts of the species range, likely resulting from a common ancestry. Only slight morphological differences were found between populations with different geographic location or habitat. The analyzes showed the distinctness of the populations from the southern part of the coast. Some unique morphological and molecular features of southern coastal populations imply that they are remnants of Late Pleistocene abundant forests. We suggest that the recent fragmentation of the Juniperus populations in the Crimean Peninsula could have arisen during the Atlantic period of the Holocene.

Abstract Strigolactones are phytohormones involved in shoot branching and hypocotyl elongation. The latter phenomenon was addressed herein by the exogenous application of a synthetic strigolactone GR24 and an inhibitor of strigolactone biosynthesis TIS108 on hypocotyls of wild type Arabidopsis and a strigolactone signalling mutant max2-1 (more axillary growth 2-1). Owing to the interdependence between light and strigolactone signalling, the present work was extended to seedling cultivation under a standard light/dark regime, or under continuous darkness. Given the essential role of the cortical microtubules in cell elongation, their organization and dynamics were characterized under the conditions of altered strigolactone signalling using fluorescence microscopy methods with different spatiotemporal capacities such as confocal laser scanning microscopy and structured illumination microscopy. It was found that the strigolactone-dependent inhibition of hypocotyl elongation correlated with changes in cortical microtubule organization and dynamics, visualized in living wild type and max2-1 seedlings stably expressing genetically-encoded fluorescent molecular markers for microtubules. Quantitative analysis of microscopic datasets revealed that chemical and/or genetic manipulation of strigolactone signalling affected microtubule remodelling, especially under light conditions. The application of GR24 and TIS108 in dark conditions partially alleviated cytoskeletal rearrangement, suggesting a new mechanistic connection between the cytoskeletal behaviour and the light-dependence of strigolactone signalling. Highlight Strigolactones regulate organization and dynamics of cortical microtubules in hypocotyl cells, which contributes to the light-mediated inhibition of hypocotyl growth in Arabidopsis seedlings. * Abbreviations BZR1 BRASSINAZOLE-RESISTANT 1 CLSM confocal laser scanning confocal microscopy COP1 CONSTITUTIVE PHOTOMORPHOGENIC 1 CRY1/2 CRYPTOCHROMES 1 and 2 CUL CULLIN DDB1 DAMAGE-BINDING PROTEIN 1 MAX2 MORE AXILLARY GROWTH2 MBD MT-binding domain of mammalian non- neuronal MICROTUBULE ASSOCIATED PROTEIN4 MDP40 MICROTUBULE DESTABILIZING PROTEIN40 MS Murashige and Skoog MT microtubules PHYA/B PHYTOCHROME A and B RBX1 RING-BOX1 SCF complex SKP1-CULLIN-F-BOX complex SIM structured illumination microscopy Skp1 S-phase kinase-associated protein 1 SL strigolactone(s) SMLX SUPPRESSOR OF MORE AXILLARY GROWTH2-LIKE TUA6 α-TUBULIN 6 WDL3 WAVE-DAMPENED 2-LIKE 3.