Rational design of Striga hermonthica-specific seed germination inhibitors

The obligate hemiparasitic weed Striga hermonthica grows on cereal roots and presents a severe threat to global food security by causing enormous yield losses, particularly in sub-Saharan Africa. The rapidly increasing Striga seed bank in infested soils provides a major obstacle in controlling this weed. Striga seeds require host-derived strigolactones (SLs) for germination, and corresponding antagonists could be used as germination inhibitors. Recently, we demonstrated that the common detergent Triton X-100 is a specific inhibitor of Striga seed germination by binding noncovalently to its receptor, S. hermonthica HYPO-SENSITIVE TO LIGHT 7 (ShHTL7), without blocking the rice (Oryza sativa) SL receptor DWARF14 (OsD14). Moreover, triazole ureas, the potent covalently binding antagonists of rice SL perception with much higher activity toward OsD14, showed inhibition of Striga but were less specific. Considering that Triton X-100 is not suitable for field application and by combining structural elements of Triton and triazole urea, we developed two hybrid compounds, KK023-N1 and KK023-N2, as potential Striga-specific germination inhibitors. Both compounds blocked the hydrolysis activity of ShHTL7 but did not affect that of OsD14. Binding of KK023-N1 diminished ShHTL7 interaction with S. hermonthica MORE AXILLARY BRANCHING 2, a major component in SL signal transduction, and increased ShHTL7 thermal specificity. Docking studies indicate that KK023-N1 binding is not covalent but is caused by hydrophobic interactions. Finally, in vitro and greenhouse tests revealed specific inhibition of Striga seed germination, which led to a 38% reduction in Striga infestation in pot experiments. These findings reveal that KK023-N1 is a potential candidate for combating Striga and a promising basis for rational design and development of further Striga-specific herbicides.

Designed strigolactone antagonists inhibit Striga seed germination.     

A biophysical model for plant cell plate maturation based on the contribution of a spreading force

Plant cytokinesis, a fundamental process of plant life, involves de novo formation of a “cell plate” partitioning the cytoplasm of dividing cells. Cell plate formation is directed by orchestrated delivery, fusion of cytokinetic vesicles, and membrane maturation to form a nascent cell wall by timely deposition of polysaccharides. During cell plate maturation, the fragile membrane network transitions to a fenestrated sheet and finally a young cell wall. Here, we approximated cell plate sub-structures with testable shapes and adopted the Helfrich-free energy model for membranes, including a stabilizing and spreading force, to understand the transition from a vesicular network to a fenestrated sheet and mature cell plate. Regular cell plate development in the model was possible, with suitable bending modulus, for a two-dimensional late stage spreading force of 2–6 pN/nm, an osmotic pressure difference of 2–10 kPa, and spontaneous curvature between 0 and 0.04 nm⁻¹. With these conditions, stable membrane conformation sizes and morphologies emerged in concordance with stages of cell plate development. To reach a mature cell plate, our model required the late-stage onset of a spreading/stabilizing force coupled with a concurrent loss of spontaneous curvature. Absence of a spreading/stabilizing force predicts failure of maturation. The proposed model provides a framework to interrogate different players in late cytokinesis and potentially other membrane networks that undergo such transitions. Callose, is a polysaccharide that accumulates transiently during cell plate maturation. Callose-related observations were consistent with the proposed model’s concept, suggesting that it is one of the factors involved in establishing the spreading force.

The late-stage onset of an “areal” spreading and stabilizing force is essential for regular plant cell plate development and maturation.     

SARS-CoV-2 membrane protein causes the mitochondrial apoptosis and pulmonary edema via targeting BOK

Deaths caused by coronavirus disease 2019 (COVID-19) are largely due to the lungs edema resulting from the disruption of the lung alveolo-capillary barrier, induced by SARS-CoV-2-triggered pulmonary cell apoptosis. However, the molecular mechanism underlying the proapoptotic role of SARS-CoV-2 is still unclear. Here, we revealed that SARS-CoV-2 membrane (M) protein could induce lung epithelial cells mitochondrial apoptosis. Notably, M protein stabilized B-cell lymphoma 2 (BCL-2) ovarian killer (BOK) via inhibiting its ubiquitination and promoted BOK mitochondria translocation. The endodomain of M protein was required for its interaction with BOK. Knockout of BOK by CRISPR/Cas9 increased cellular resistance to M protein-induced apoptosis. BOK was rescued in the BOK-knockout cells, which led to apoptosis induced by M protein. M protein induced BOK to trigger apoptosis in the absence of BAX and BAK. Furthermore, the BH2 domain of BOK was required for interaction with M protein and proapoptosis. In vivo M protein recombinant lentivirus infection induced caspase-associated apoptosis and increased alveolar-capillary permeability in the mouse lungs. BOK knockdown improved the lung edema due to lentivirus-M protein infection. Overall, M protein activated the BOK-dependent apoptotic pathway and thus exacerbated SARS-CoV-2 associated lung injury in vivo. These findings proposed a proapoptotic role for M protein in SARS-CoV-2 pathogenesis, which may provide potential targets for COVID-19 treatments.Subject terms: Infectious diseases, Immunopathogenesis

In SARS-CoV-2-infected lung epithelial cells, endodomain of M protein binds to the BH2 domain of BOK and inhibits ubiquitination. BOK is stabilized and translocate to the mitochondrial outer membrane, promoting Cyt c release. Cyt c released outside the mitochondria activates CASP 9 mediated apoptosis, thereby inducing pulmonary edema.     

Epimers from the leaves of Calophyllum inophyllum

The ethanolic extract of the fresh leaves of Calophyllum inophyllum afforded a pair of new epimers named as inophynone and isoinophynone. Their structures were elucidated with the aid of spectroscopic techniques. Some known constituents, cholesterol, friedelin, canophyllol and canophyllic acid, were also isolated from the same source.     

An insight into molecular taxonomy of bufonids,microhylids, and dicroglossid frogs: First genetic records from Pakistan

The current study was focused on documentation of amphibian assemblage in North Punjab and Islamabad Capital Territory, Pakistan, by using mitochondrial gene sequences of 16S rRNA. Our study entailed 37% of the known amphibian species of the country. We provided a phylogenetic analysis based on 74 newly generated mitochondrial 16S rRNAs from nine species of genus Microlyla, Duttaphrynus, Allopaa, Nanorana, Sphaerotheca, Minervarya, Hoplobatrachus, and Euphlyctis. We employed the maximum‐likelihood inference and Bayesian analysis to assess the taxonomic status of the samples obtained from Pakistan, with respect to other congeneric species from surrounding regions. Our findings confirmed the taxonomic status of South Asian anuran species Duttaphrynus stomaticus, Duttaphrynus melanostictus, Microhyla nilphamariensis, Allopaa hazarensis, Nanorana vicina, Sphaerotheca maskeyi (synonym: S. pashchima), Minervarya pierrei, Hoplobatrachus tigerinus, and Euphlyctis kalasgramensis in Pakistan. We have reported new country records of genus Minervarya ( M. pierrei). Minervarya pierrei was previously misidentified as Fejervarya limnocharis, due to dearth of genetic information. We provided the first genetic records of our endemic species N. vicina. The results revealed the taxonomic placement of N. vicina with respect to its congeners and validated the taxonomic status of N. vicina from its type locality (Murree) for the first time. The findings of the present study also indicated the paraphyletic relationship of A.‐ hazarensis with Nanorana species. So, based on our phylogenetic inferences, morphological characters, and habitat preferences, validity of generic status of A. hazarensis is undecided. As our data were not enough to resolve this issue, we suggest sequencing of additional mitochondrial and nuclear genes in the future studies to get a better resolution. We recommend carrying out extensive surveys throughout the country for proper scientific documentation of amphibians of Pakistan. Many new species, some of them might be endemic to Pakistan, are expected to be discovered, and taxonomic status of other species would be resolved.     

Slippery Photothermal Trap for Outstanding Deicing Surfaces

Ice accumulation is a safety and operational threat in power lines,wind turbines,and transportations.Surfaces having both passive anti-icing and active deicing ...     

Genotypic variation for drought tolerance in cotton (Gossypium hirsutum L.): Leaf gas exchange and productivity

Although water-limited environments are detrimental to cotton growth and productivity worldwide, identification of cotton (Gossypium hirsutum L.) genotypes that are less sensitive to drought may improve productivity in drought prone areas. The objective of the study was to assess genotypic variation for drought tolerance in cotton varieties using physiological attributes as selection criteria, and to determine the relationship of physiological attributes with productivity traits. The association of target physiological traits for drought tolerance (photosynthetic rate (P_n), stomatal conductance (g_s), and transpiration rate (E)) with productivity traits under well-watered (W₁) and water-limited (W₂) regimes was analyzed using 32 public cotton cultivars/bred lines in two field experiments conducted during the normal cotton growing seasons 2003 and 2004. Seed cotton yield (SCY) and biological yield (BY) were markedly affected under W₂ regime in all cultivars except the outstanding performance of CIM-1100 and RH-510 proving their superiority to other cultivars in drought tolerance. Conversely, FH-901, FH-634, and FH-2000 were high yielding under W₁ regime; however, exhibited a sharp decline in yield under W₂ regime. A positive correlation between SCY and BY under water stress (r=0.44 in 2003; r=0.69 in 2004) indicates that BY is also a primary determinant of SCY under water stress and genetic improvement of BY under water-limited environment may also improve SCY. P_n, g_s, and E were significantly reduced by water stress. Substantial genotypic variation for gas exchange attributes existed among the cotton cultivars. A positive association (P<0.01) was observed between g_s and E under both regimes in both years indicating the prevalence of stomatal control of transpiration. The positive association (P<0.01) between P_n and g_s in both years in W₂ regime indicates also a major role of stomatal effects in regulating leaf photosynthesis under water-limited conditions. P_n was significantly correlated with SCY (P<0.01) and BY (P<0.05 in 2003; P<0.01 in 2004) in W₂ regime; however, the level of these associations was not significant in W₁ regime. These findings demonstrate that association of P_n with productivity is effective under water-limited environment and may be useful as a selection criterion in breeding programs with the objective of improving drought tolerance and SCY under water-limited environments. Moreover, association between SCY and BY under water stress suggests that genetic improvement of BY under water stress may also improve SCY.