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Maize (Zea mays) is a major staple crop in Africa, where its yield and the livelihood of millions are compromised by the parasitic witchweed Striga. Germination of Striga is induced by strigolactones exuded from maize roots into the rhizosphere. In a maize germplasm collection, we identified two strigolactones, zealactol and zealactonoic acid, which stimulate less Striga germination than the major maize strigolactone, zealactone. We then showed that a single cytochrome P450, ZmCYP706C37, catalyzes a series of oxidative steps in the maize-strigolactone biosynthetic pathway. Reduction in activity of this enzyme and two others involved in the pathway, ZmMAX1b and ZmCLAMT1, can change strigolactone composition and reduce Striga germination and infection. These results offer prospects for breeding Striga-resistant maize. [ABSTRACT FROM AUTHOR]

Abstract: Emerging concepts of membrane organization point to the compartmentalization of the plasma membrane into distinct lipid microdomains. This lateral segregation within cellular membranes is based on cholesterol–sphingolipid-enriched microdomains or lipid rafts which can move laterally and assemble into large-scale domains to create plasma membrane specialized cellular structures at specific cell locations. Such domains are likely involved in the genesis of the postsynaptic specialization at the neuromuscular junction, which requires the accumulation of acetylcholine receptors (AChRs), through activation of the muscle specific kinase MuSK by the neurotropic factor agrin and the reorganization of the actin cytoskeleton. We used C2C12 myotubes as a model system to investigate whether agrin-elicited AChR clustering correlated with lipid rafts. In a previous study, using two-photon Laurdan confocal imaging, we showed that agrin-induced AChR clusters corresponded to condensed membrane domains: the biophysical hallmark of lipid rafts [F. Stetzkowski-Marden, K. Gaus, M. Recouvreur, A. Cartaud, J. Cartaud, Agrin elicits membrane condensation at sites of acetylcholine receptor clusters in C2C12 myotubes, J. Lipid Res. 47 (2006) 2121–2133]. We further demonstrated that formation and stability of AChR clusters depend on cholesterol. We also reported that three different extraction procedures (Triton X-100, pH 11 or isotonic Ca++, Mg++ buffer) generated detergent resistant membranes (DRMs) with similar cholesterol/GM1 ganglioside content, which are enriched in several signalling postsynaptic components, notably AChR, the agrin receptor MuSK, rapsyn and syntrophin. Upon agrin engagement, actin and actin-nucleation factors such as Arp2/3 and N-WASP were transiently recovered within raft fractions suggesting that the activation by agrin can trigger actin polymerization. Taken together, the present data suggest that AChR clustering at the neuromuscular junction relies upon a mechanism of raft coalescence driven by agrin-elicited actin polymerization. [Copyright &y& Elsevier]

The endosomal system provides rich signal processing capabilities for responses elicited by growth factor receptors and their ligands. At the single cell level, endosomal trafficking becomes a critical component of signal processing, as exemplified by the epidermal growth factor (EGF) receptors. Activated EGFRs are trafficked to the phosphatase-enriched peri-nuclear region (PNR), where they are dephosphorylated and degraded. The details of the mechanisms that govern the movements of stimulated EGFRs towards the PNR, are not completely known. Here, exploiting the advantages of lattice light-sheet microscopy, we show that EGFR activation by EGF triggers a transient calcium increase causing a whole-cell level redistribution of Adaptor Protein, Phosphotyrosine Interacting with PH Domain And Leucine Zipper 1 (APPL1) from pre-existing endosomes within one minute, the rebinding of liberated APPL1 directly to EGFR, and the dynein-dependent translocation of APPL1-EGF-bearing endosomes to the PNR within ten minutes. The cell spanning, fast acting network that we reveal integrates a cascade of events dedicated to the cohort movement of activated EGF receptors. Our findings support the intriguing proposal that certain endosomal pathways have shed some of the stochastic strategies of traditional trafficking and have evolved processes that provide the temporal predictability that typify canonical signaling. York et al employ lattice light-sheet microscopy to study the initial events following activation of the epidermal growth factor receptor (EGFR) in whole live cells. They find that APPL1 relocates from pre-existing endosomes, triggered by calcium, to EGFR puncta which results in a cohort, dynein mediated movement of EGFR towards the peri-nuclear region of the cell, expanding our understanding of EGFR trafficking dynamics. [ABSTRACT FROM AUTHOR]

Abstract: We report on the design and fabrication of porous silicon based rugate filters. We have achieved narrow line-width, high reflectivity optical filters made entirely from silicon by continuously varying of the refractive index of Si and apodizing the index profile of the structure. [Copyright &y& Elsevier]