RESUMO
Slime expelled by velvet worms entraps prey insects within seconds in a hardened biopolymer network that matches the mechanical strength of industrial polymers. While the mechanic stimuli-responsive nature and building blocks of the polymerization are known, it is still unclear how the velvet worms' slime hardens so fast. Here, we investigated the slime for the first time, not only after, but also before expulsion. Further, we investigated the slime's micro- and nanostructures in-depth. Besides the previously reported protein nanoglobules, carbohydrates, and lipids, we discovered abundant encapsulated phosphate and carbonate salts. We also detected CO2 bubbles during the hardening of the slime. These findings, along with further observations, suggest that the encapsulated salts in expelled slime rapidly dissolve and neutralize in a baking-powder-like reaction, which seems to accelerate the drying of the slime. The proteins' conformation and aggregation are thus influenced by shear stress and the salts' neutralization reaction, increasing the slime's pH and ionic strength. These insights into the drying process of the velvet worm's slime demonstrate how naturally evolved polymerizations can unwind in seconds, and could inspire new polymers that are stimuli-responsive or fast-drying under ambient conditions.
Assuntos
Nanoestruturas , Sais , Proteínas/química , Biopolímeros , Concentração OsmolarRESUMO
Intensive exploitation of mahogany wood (Swietenia macrophylla, Meliaceae) has resulted in the loss of natural populations. Somatic embryogenesis offers an alternative to clonal propagation and conservation of mahogany. This study describes biochemical (carbohydrates, total phenols, total flavonoids, protein, and plant growth regulators content) and histological characteristics of the somatic embryogenesis process in mahogany. Calli were obtained by culturing cotyledons of seeds from immature fruits for six weeks on semi-solid MS medium supplemented with 1.0 mgL-1 of kinetin and 4.0 mgL-1 of 2, 4-D. Primary callus was cultured on half strength semi-solid MS medium supplemented with 1.0 mgl-1 6-BA (6-benzylaminopurine) and embryogenic structures were obtained. Embryo development from globular-shaped somatic embryos to the cotyledonary stage was confirmed by histology and scanning electron microscopy. Shoot initiation was observed after somatic embryos were transferred to germination and maturation medium. Endogenous concentrations of carbohydrates, total phenols, total flavonoids, protein, and plant growth regulators were determined in embryogenic (EC) and non-embryogenic (NEC) calli of mahogany. Embryogenic cultures contained significantly higher concentrations of IAA (indoleacetic acid), ABA (abscisic acid), and GAs (Gibberellins 1+3+20), whereas non-embryogenic calli contained more total phenols, flavonoids and resistant starch. Fructose and glucose were not present at detectable levels in EC or NEC, whereas soluble starch and sucrose were only detectable in EC. Concentrations of total proteins, Z/ZR (Zeatin/zeatin riboside) and iP/iPA (N6-(Δ2-isopentenyl) adenine and N6-(Δ2-isopentenyl) adenosine) were similar in EC and NEC.
La explotación intensiva de la madera de caoba (Swietenia macrophylla) ha provocado la pérdida de poblaciones naturales. La embriogénesis somática ofrece una alternativa a la propagación clonal y la conservación de esta especie. Este estudio describe las características bioquímicas (contenido de carbohidratos, fenoles totales, flavonoides totales, proteínas y reguladores del crecimiento) e histológicas del proceso de embriogénesis somática en caoba. Los callos se obtuvieron cultivando cotiledones de semillas de frutos inmaduros durante seis semanas en medio MS semisólido suplementado con 1.0 mgL-1 de kinetina y 4.0 mgL-1 de 2, 4-D. Luego se cultivó el callo primario en medio MS semisólido y un suplemento de 1.0 mgl-1 BA y se obtuvieron estructuras embriogénicas. El desarrollo de embriones somáticos de forma globular a la etapa cotiledonar se confirmó por histología y microscopía electrónica de barrido. La iniciación del brote se observó después de que los embriones somáticos se transfirieron a un medio de germinación y maduración. Se determinaron las concentraciones endógenas de carbohidratos, fenoles totales, flavonoides totales, proteínas y reguladores del crecimiento en callos embriogénicos (EC) y no embriogénicos (NEC) de caoba. Los cultivos embriogénicos contenían concentraciones significativamente más altas de IAA, ABA y GA, mientras que los callos no embriogénicos contenían más fenoles totales, flavonoides y almidón resistente. La fructosa y la glucosa no estaban presentes en niveles detectables en EC o NEC, mientras que el almidón soluble y la sacarosa solo se detectaron en el EC. Las concentraciones de proteínas totales, Z / ZR e iP / iPA fueron similares en EC y NEC.