Cytogenetic effect of some nanostructure polymers prepared via gamma irradiation on Vicia faba plant

Background Nourishment plants during the field time is a must; to have healthy, high productive and self-propagating plants. The trendy nano-fertilizers came to the front in modernized agriculture seeking for minimizing the soil suffocation with other chemical fertilizers in the bulk size. Nano-fertilizers may represent a way out of shot as they are completely absorbed by plant due to their small size, also it magnifies the benefit to the plant due to its high surface area. Nano-fertilizers are introduced via different way of synthesis methods. In this work, three of new nanocomposites are prepared in nano form via Gamma irradiation from Cobalt 60 source at irradiation dose 5 KGy. These composites which can supply plants with P, Zn elements needs to be revised for their safety usage in agriculture. Methodology Three compounds; Zinc oxide, phosphorous and the mixed Zinc–phosphorous elements were prepared in nano-composite forms coated with PVP as a shell and then characterized by HR-TEM, UV and FT-IR to emphasize their new sizes and shapes, then, they were examined for their cytotoxicity in three concentrations (0.5, 1 and 2%) on Vicia faba plants; after 3 h of direct roots treatment. Cytotoxicity test concerned the mitotic index, phase index, abnormal mitosis and the type of the aberrations at each phase. Results The three tested NPs exerted mito-accelerating effect on root meristematic cells. However, concentration‐dependent genotoxicity was also an evident. Conclusion The three examined nano-composites may recommend to be used in the lowest examined concentrations to minimize its harm effect on the plant cell and keep their benefits to the environment. It also recommended to count the Zn/P mix NPs over ZN or P separately as it induces an intermediating cytogenetic effect on mitosis apparatus of Vicia faba plant. Graphical Abstract

ABA represses TOR and root meristem activity through nuclear exit of the SnRK1 kinase

The phytohormone abscisic acid (ABA) promotes plant tolerance to major stresses like drought, partly by modulating plant growth and development. However, the underlying mechanisms are poorly understood. Here, we show that cell proliferation in the Arabidopsis thaliana root meristem is controlled by the interplay between three kinases, SNF1-RELATED KINASE 2 (SnRK2), the main driver of ABA signaling, the SnRK1 energy sensor, and the growth-promoting TARGET OF RAPAMYCIN (TOR) kinase. Under favorable conditions, the SnRK1α1 catalytic subunit is enriched in the nuclei of root meristematic cells and this is accompanied by normal cell proliferation and meristem size. Depletion of SnRK2s in a snrk2.2 snrk2.3 double mutant causes constitutive cytoplasmic localization of SnRK1α1 and a reduction in meristem size, suggesting that, under non-stress conditions, SnRK2s enable growth by retaining SnRK1α1 in the nucleus. In response to elevated ABA levels, SnRK1α1 translocates to the cytoplasm and this is accompanied by inhibition of TOR, decreased cell proliferation and meristem size. Blocking nuclear export with leptomycin B abrogates ABA-driven SnRK1α1 relocalization to the cytoplasm and the inhibition of TOR. Fusion of SnRK1α1 to an SV40 nuclear localization signal leads to defective TOR repression in response to ABA, demonstrating that SnRK1α1 nuclear exit is a premise for this repression. Finally, the SnRK2-dependent changes in SnRK1α1 subcellular localization are specific to the proliferation zone of the meristem, underscoring the relevance of this mechanism for growth regulation.

Short-term changes related to autotetraploidy in essential oil composition of Eucalyptus benthamii Maiden & Cambage and its applications in different bioassays

Some forest trees have been polyploidized to improve their traits and to supply new germplasms for breeding programs. As trees have a long juvenile stage, the early characterization of the chromosome set doubling effects is crucial for previous selection. Thus, we aimed to characterize the chemical variability of essential oils from diploid and autotetraploid germplasms (autotetraploid A and B) of Eucalyptus benthamii, as well as to evaluate their larvicidal and allelopathic effects. Autotetraploid A showed a higher essential oil yield than diploid and autotetraploid B, which did not differ quantitatively. Aromadendrene, viridiflorol and α-pinene were the major compounds in the diploid essential oil. In contrast, compounds were present in autotetraploids, such as 1,8-cineole, limonene, α-terpineol, and α-terpinyl-acetate. Essential oils from the diploid at 50–200 ppm were twice as larvicidal than those from autotetraploids against Aedes aegypti larvae. Considering the phytotoxicity bioassays using Lactuca sativa, essential oils from both ploidy levels affected root growth. Moreover, the essential oils inhibited shoot growth at all concentrations tested (187.5; 375; 750; 1500; and 3000 ppm). Autotetraploid A and B had the same effect on shoot growth as glyphosate. The essential oils had no cytogenotoxic effect on root meristematic cells of L. sativa, whereas phytotoxic potential was identified mainly in shoot growth. This work demonstrated a dramatic change in secondary metabolism (terpene composition) related to an increase in the ploidy level in Eucalyptus germplasms. In addition, we report the novelty of the chemical composition of essential oils among germplasms and their potential use as larvicidal and post-emergence weed control agents.

A Perspective on Adventitious Root Formation in Tree Species

Adventitious root formation is an organogenic process, regulated at several levels, that is crucial for the successful vegetative propagation of numerous plants. In many tree species, recalcitrance to adventitious root formation is a major limitation in the clonal propagation of elite germplasms. Information on the mechanisms underlying the competence for adventitious root formation is still limited. Therefore, increasing our understanding of the mechanisms that enable differentiated somatic cells to switch their fates and develop into root meristematic cells, especially those involved in cell developmental aging and maturation, is a priority in adventitious root-related research. The dynamic cell wall–cytoskeleton, along with soluble factors, such as cellular signals or transcriptional regulators, may be involved in adult cell responses to intrinsic or extrinsic factors, resulting in maintenance, induction of root meristematic cell formation, or entrance into another differentiating pathway.

Karyotype evolution of the genus Eranthis Salisb. (Ranunculaceae)

We have conducted comparative study of karyotypes for nine Eranthis Salisb. species: E. bulgarica (Stef.)Stef., E. hyemalis (L.) Salisb., E. longistipitata Regel (section Eranthis), E. byunsanensis B. Y. Sun, E. lobulata W. T.Wang, E. pinnatifida Maxim., E. sibirica DC., E. stellata Maxim., and E. tanhoensis Erst (section Shibateranthis). Thespecies-specifity of karyotypes was established for all species investigated. The chromosomes of each species weremedium or large in size (4–12 µm). Besides E. sibirica and E. tanhoensis, all the investigated specimens had diploidcytotypes with 2n = 16 and the basic chromosome number x = 8. Plants from five E. sibirica populations were tetraploidand hexaploid with x = 7, 2n = 28 and 2n = 42 respectively. Plants from seven E. tanhoensis populations were diploid withx = 7 and 2n = 14. Diploid karyotypes of Eranthis included 4–5 pairs of large equal-armed (metacentric) chromosomes,and 2–4 pairs of unequal-armed chromosomes belonging to different morphological types (submetacentric, subtelocentric,and acrocentric ones). We have revealed B chromosomes in root meristematic cells of E. lobulata and E. tanhoensis forthe first time. We suppose that the key developments in Eranthis karyotype`s evolution were pericentric inversions,polyploidy, and probably translocations.

Evaluation of the bio-toxicity and cytogenetic effects of methanolic leaf extract of Heliotropium indicum L.

Heliotropium indicum L. has been shown to be very important in traditional healing medicine. However, many reports have indicated that the toxicity is not unconnected with pharmaceutical properties. This study therefore investigated the cytotoxic, genotoxic and biotoxic activities of methanolic leaf extract of H. indicum using Brine Shrimp lethality assay. The results revealed that the leaf extract of H. indicum showed lethality against the Brine Shrimps nauplii. The highest mortality was recorded at a concentration of 1000 μg/ml. The LC50 value of the Brine Shrimps mortality of the extract was recorded to be 461.04±10.02 μg/ml. In addition, the extract inhibited mitotic division in A. cepa root meristematic cells. The mitotic index was reduced from 59.99% in the control to 2.2% at 1000 μg/ml of the leaf extract. Chromosomal aberrations were observed at different concentrations. These include sticky chromosomes at metaphase and anaphase, chromosome breakage, degenerated and disoriented chromosomes at metaphase plate. It can be concluded from this present study that methanolic leaf extract of H. indicum was cytotoxic and genotoxic to Brine Shrimps and A. cepa cells respectively. Hence, caution should be exercised with respect to the consumption of H. indicum leaf in any form. © 2020 International Formulae Group. All rights reserved. Keywords: Mitotic index, chromosome aberrations, Brine Shrimps Lethality assay, Allium cepa assay, leaf extract

Redox response of iron-sulfur glutaredoxin GRXS17 activates its holdase activity to protect plants from heat stress

ABSTRACTLiving organisms use a large panel of mechanisms to protect themselves from environmental stress. Particularly, heat stress induces misfolding and aggregation of proteins which are guarded by chaperone systems. Here, we examine the function the glutaredoxin GRXS17, a member of thiol reductases families in the model plant Arabidopsis thaliana. GRXS17 is a nucleocytosolic monothiol glutaredoxin consisting of an N-terminal thioredoxin (TRX)-domain and three CGFS-active site motif-containing GRX-domains that coordinate three iron-sulfur (Fe-S) clusters in a glutathione (GSH)-dependent manner. As a Fe-S cluster-charged holoenzyme, GRXS17 is likely involved in the maturation of cytosolic and nuclear Fe-S proteins. In addition to its role in cluster biogenesis, we showed that GRXS17 presents both foldase and redox-dependent holdase activities. Oxidative stress in combination with heat stress induces loss of its Fe-S clusters followed by subsequent formation of disulfide bonds between conserved active site cysteines in the corresponding TRX domains. This oxidation leads to a shift of GRXS17 to a high-MW complex and thus, activates its holdase activity. Moreover, we demonstrate that GRXS17 is specifically involved in plant tolerance to moderate high temperature and protects root meristematic cells from heat-induced cell death. Finally, we showed that upon heat stress, GRXS17 changes its client proteins, possibly to protect them from heat injuries. Therefore, we propose that the iron-sulfur cluster enzyme glutaredoxin GRXS17 is an essential guard to protect proteins against moderate heat stress, likely through a redox-dependent chaperone activity. All in all, we reveal the mechanism of an Fe-S cluster-dependent activity shift, turning the holoenzyme GRXS17 into a holdase that prevents damage caused by heat stress.

Relationships between land use and water quality obtained for the evaluation of genotoxic effects in plant bioindicators

Anthropic activities as well as land use and occupation are closely linked to water and soil quality. An alternative to assess their influence on water quality in water bodies is through biomonitoring using Allium cepa as a bioindicator organism. This technique allows the detection of cytogenetic abnormalities in Allium cepa root meristematic cells after contact with analyzed water samples. Thus, we evaluated the genotoxic potential of water samples from the Rio das Antas (Antas River) along the urban perimeter of the city of Irati, Paraná, Brazil. With the aid of GeoEye Satellite high-resolution fused orbital images, we searched for possible relationships between the use and occupation of land around this river. Biomonitoring was performed at three different sampling points. Statistical equality between the negative control and Point 1 and between Points 2 and 3 was obtained using Fisher's test and a Principal Coordinate Analysis (PCoA). The former presented a low frequency of abnormalities chromosomes and the latter presented larger averages. In addition, Point 1 had strong influence of tree vegetation. Points 2 and 3, demonstrated a strong influence of urbanized area, with significant degradation of permanent preservation areas (áreas de preservação permanente – (APP). The results showed remarkable anthropogenic interference to the ecosystem. Furthermore, this indicates importance of an APP watercourses functioning to preserve the quality of the water resources.