RESUMO
Sprouting angiogenesis is fundamental for development and contributes to cancer, diabetic retinopathy, and cardiovascular diseases. Sprouting angiogenesis depends on the invasive properties of endothelial tip cells. However, there is very limited knowledge on how tip cells invade into tissues. Here, we show that endothelial tip cells use dactylopodia as the main cellular protrusion for invasion into nonvascular extracellular matrix. We show that dactylopodia and filopodia protrusions are balanced by myosin IIA (NMIIA) and actin-related protein 2/3 (Arp2/3) activity. Endothelial cell-autonomous ablation of NMIIA promotes excessive dactylopodia formation in detriment of filopodia. Conversely, endothelial cell-autonomous ablation of Arp2/3 prevents dactylopodia development and leads to excessive filopodia formation. We further show that NMIIA inhibits Rac1-dependent activation of Arp2/3 by regulating the maturation state of focal adhesions. Our discoveries establish a comprehensive model of how endothelial tip cells regulate its protrusive activity and will pave the way toward strategies to block invasive tip cells during sprouting angiogenesis.
Assuntos
Células Endoteliais/citologia , Miosina não Muscular Tipo IIA/genética , Pseudópodes/genética , Proteínas rac1 de Ligação ao GTP/genética , Complexo 2-3 de Proteínas Relacionadas à Actina/química , Complexo 2-3 de Proteínas Relacionadas à Actina/genética , Animais , Extensões da Superfície Celular , Células Endoteliais/metabolismo , Camundongos , Neovascularização Patológica/genética , Neovascularização Fisiológica/genética , Miosina não Muscular Tipo IIA/química , Ativação Transcricional/genéticaRESUMO
A high molecular weight humic fraction (>3,500 Da) was characterized chemically by DRIFT and 1H NMR spectroscopy, and was applied to Zea mays L. plants to evaluate its effect on phenylpropanoid metabolism. The activity and gene expression of phenylalanine (tyrosine) ammonia-lyase (PAL/TAL), and the concentrations of phenolics and their amino acid precursors phenylalanine and tyrosine were assayed. Maximum induction of PAL/TAL activity and expression was obtained when the concentration of added humic substance was 1 mg C/l hydroponic solution. Phenylalanine and tyrosine significantly decreased (-16% and -22%, respectively), and phenolic compounds increased in treated plants. The effects of the humic substance could be ascribed partly to indoleacetic acid (27 nmol/mg C) in the humic fraction. Our results suggest that this humic fraction induces changes in phenylpropanoid metabolism. This is the first study that shows a relationship between humic substances and the phenylpropanoid pathway.
Assuntos
Substâncias Húmicas , Fenóis/metabolismo , Zea mays/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Espectroscopia de Ressonância Magnética , Fenilalanina/metabolismo , Fenilalanina Amônia-Liase/genética , Fenilalanina Amônia-Liase/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier , Tirosina/metabolismo , Zea mays/enzimologiaRESUMO
The growing concern on long-term productivity of agroecosystems has emphasized the need to develop management strategies to maintain and protect soil resources, particularly soil organic matter (SOM). Among these, the composting process allows both recycling of the increasing amount of organic waste materials and restoration of the content of organic matter in soil. A sequential chemical fractionation into structurally unbound (SU), weakly bound (WB) and strongly bound (SB) compounds was applied to a bulk compost, and its soluble fractions were extracted in water, either after oxidation of compost suspension with an oxygen flux (TEA), or without oxidation but separated into hydrophilic (HiDOM) and hydrophobic (HoDOM) components. The ratio of hydrophilic over hydrophobic compounds decreased in the order HiDOM > TEA > compost > HoDOM, while TEA and compost showed the largest content of SU and WB components, respectively. Such chemically characterized bulk compost and fractions were tested on maize seedlings grown in sand and in hydroponic conditions, and the effects on plant growth and nitrogen metabolism were measured. The structurally complex bulk compost and the hydrophobic HoDOM fraction negatively affected plant growth, whereas the hydrophilic and less-structured fractions (HiDOM and TEA) showed large positive effects on both growth and enzymatic activities of plants. These results suggest that composted organic matter can become useful to stimulate plant growth if the content of potentially bioavailable hydrophilic and poorly structured components is large. These components may be progressively separated from the compost matrix and contribute to the dynamics of natural organic matter in soil.