SEARCH · Search NASA

Results for “Endoplasmic Reticulum/physiology”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

7 records

All sources NASA NTRS DOE OSTI

NASA NTRS2000

Arabinogalactan protein and wall-associated kinase in a plasmalemmal reticulum with specialized vertices

Arabinogalactan protein and wall-associated kinase (WAK) are suspected to be regulatory players at the interface between cytoplasm and cell wall. Both WAK(s) and arabinogalactan shown likely to represent arabinogalactan protein(s) have been visualized there with computational optical-sectioning microscopy. The arabinogalactan occurs in a polyhedral array at the external face of the cell membrane. WAK, and other proteins as yet unidentified, appear to fasten the membrane to the wall at vertices of the array. Evidence is presented that the array bears an important part of the mechanical stress experienced by the membrane, and it is speculated that the architectural organization of arabinogalactan protein, WAK, and other components of the array is critical for coordination of endomembrane activities, growth, and differentiation. The array has been named the plasmalemmal reticulum.

NASA Discipline Plant Biology↗

NASA NTRS1997

Stereological analysis of gravitropism in protonemata of the moss Ceratodon

Apical cells of dark-grown protonemata of the moss Cerotodon purpureus are negatively gravitropic. Previous light microscopy has shown that reorientation to the horizontal induces amyloplast sedimentation and redistribution of microtubules. To determine whether other components become redistributed laterally or axially, the apical 35 micrometers of both vertical and horizontal apical cells were compared stereologically using transmission electron microscopy. Reorientation to the horizontal changed the longitudinal distributions of tubular ER, Golgi stacks, and vesicles but not cisternal ER, mitochondria, and plastids. Only plastids showed a statistically significant lateral redistribution after horizontal placement. Qualitative examination of the sedimentation zone showed plastids sedimented close to peripherally located ER with vacuoles displaced above plastids. These results argue against a model where differential tip growth results from a redistribution of Golgi stacks or exocytic vesicles.

Non-NASA Center↗

NASA NTRS1997

The endomembrane sheath: a key structure for understanding the plant cell?

Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

NASA Discipline Plant Biology↗

NASA NTRS1996

Dynamics of vegetative cytoplasm during generative cell formation and pollen maturation in Arabidopsis thaliana

Ultrastructural changes of pollen cytoplasm during generative cell formation and pollen maturation in Arabidopsis thaliana were studied. The pollen cytoplasm develops a complicated ultrastructure and changes dramatically during these stages. Lipid droplets increase after generative cell formation and their organization and distribution change with the developmental stage. Starch grains in amyloplasts increase in number and size during generative and sperm cell formation and decrease at pollen maturity. The shape and membrane system of mitochondria change only slightly. Dictyosomes become very prominent, and numerous associated vesicles are observed during and after sperm cell formation. Endoplasmic reticulum appears extensively as stacks during sperm cell formation. Free and polyribosomes are abundant in the cytoplasm at all developmental stages although they appear denser at certain stages and in some areas. In mature pollen, all organelles are randomly distributed throughout the vegetative cytoplasm and numerous small particles appear. Organization and distribution of storage substances and appearance of these small particles during generative and sperm cell formation and pollen maturation are discussed.

Non-NASA Center↗

NASA NTRS1987

Influence of microgravity on root-cap regeneration and the structure of columella cells in Zea mays

We launched imbibed seeds and seedlings of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on 1) root-cap regeneration, and 2) the distribution of amyloplasts and endoplasmic reticulum (ER) in the putative statocytes (i.e., columella cells) of roots. Decapped roots grown on Earth completely regenerated their caps within 4.8 days after decapping, while those grown in microgravity did not regenerate caps. In Earth-grown seedlings, the ER was localized primarily along the periphery of columella cells, and amyloplasts sedimented in response to gravity to the lower sides of the cells. Seeds germinated on Earth and subsequently launched into outer space had a distribution of ER in columella cells similar to that of Earth-grown controls, but amyloplasts were distributed throughout the cells. Seeds germinated in outer space were characterized by the presence of spherical and ellipsoidal masses of ER and randomly distributed amyloplasts in their columella cells. These results indicate that 1) gravity is necessary for regeneration of the root cap, 2) columella cells can maintain their characteristic distribution of ER in microgravity only if they are exposed previously to gravity, and 3) gravity is necessary to distribute the ER in columella cells of this cultivar of Z. mays.

NASA Discipline Number 00-00↗

NASA NTRS1988

Structural correlates of imbibitional injury in Typha pollen

The ultrastructure of Typha latifolia pollen was examined as a function of pollen moisture content and incubation temperature, in order to identify possible lesions induced by imbibitional chilling. A syndrome of structural traits was found which characterizes damaged grains. Compared to viable grains, the protoplast of damaged pollen has a higher proportion of its volume occupied by vesicles, and less volume occupied by cytoplasm. Damaged grains also tend to have dilated cisternae of endoplasmic reticulum, larger starch grains and lipid bodies, poorly preserved mitochondria and membranes, and, sometimes, numerous electron-dense globules associated with membranes. The percentage of grains exhibiting this damage syndrome correlates closely with the number of ungerminated grains in most samples, regardless of moisture content or incubation temperature. Injury due to rapid imbibition from the dry state or to imbibitional chilling appear to be similar structurally, regardless of whether the stresses are imposed singly or together. The injury is not confined to one cell component (e.g., mitochondria), but may involve a generalized disruption of membranes. These results suggest that similar stress responses are elicited by imbibition from the dry state and by imbibitional chilling.

NASA Program Space Biology↗

NASA NTRS1991

Plant gravity sensing

This review of plant gravity sensing examines sensing in organ gravitropism, sensing in single-cell gravitropism, and nongravitropic sensing. Topics related to sensing in organ gravitropism are (1) identification of the gravitropic susceptors, including intracellular asymmetry in equilibrium position and after reorientation, susceptor signal-to-noise ratio, signal integration over threshold stimulation periods, intracellular asymmetry and gravitropic competence, and starch deficiency and gravitropic competence; (2) possible root statocytes and receptors, including identification of presumptive statocytes, cytology, and possible receptors and models of sensing; and (3) negatively gravitropic organs, including identification and distribution of presumptive statocytes and cytology and possible receptors. Topics related to nongravitropic sensing include gravitaxis, reaction wood, gravimorphogenesis, other gravity-influenced organ movements, and cytoplasmic streaming.

Non-NASA Center↗