15 research outputs found
Characterization of caspase-like proteolytic activities during programmed cell deth in the nucellus of Sechium edule
Programmed cell death of the nucellus during Sechium edule SW seed development is associated with activation of gaspase-like proteases
The nucellus is a maternal tissue that embeds and
feeds the developing embryo and secondary endosperm.
During seed development, the cells of the
nucellus suffer a degenerative process soon after
fertilization as the cellular endosperm expands and
accumulates reserves. Nucellar cell degeneration has
been considered to be a form of developmentally
programmed cell death (PCD). It was investigated
whether or not this degenerative process is characterized
by apoptotic hallmarks. Evidence showed that cell
death is mostly localized in the border region of the
tissue adjacent to the expanding endosperm. Cell
death is accompanied by profound changes in the
morphology of the nuclei and by a huge degradation of
nuclear DNA. Moreover, an increase of activity of
different classes of proteinases is reported, and the
induction of caspase-like proteases sensitive to specific
inhibitors was detected. Nucellar caspase-like
proteases are characterized by an acid pH optimum
suggesting a possible localization in the vacuole
Hydrolysis of gliadin during germination of wheat seeds
The in vivo degradation of gliadin has been studied using sodium dodecyl sulfate-polyacrylamide gel
electrophoresis and reversed-phase high performance liquid chromatography. Both analyses show the appearance
of a small number of degradation products and the early disappearance of some gliadin components
during the course of germination. These components thus appear to be subject to preferential
breakdown, the w-gliadin fraction being the first to be degraded. The in vitro degradation of total gliadin
or selected gliadin fractions, performed by the main endopeptidase appearing during wheat germination,
reveals a transient accumulation of intermediates, which were subsequently degraded to small peptides.
These data suggest that the relatively small amount of intermediates formed during wheat germination
might be due to the concerted action of the cysteine proteinase and of the carboxypeptidases. Since these
enzymes have high activities during the course of seed germination, they might cause a rapid degradation
of intermediates before they can accumulat
Changes in Histones/DNA Ratio in Scutellum Nuclei During Ageing of Triticum Durum
SUMMARYColumnar epithelium and parenchyma cells of the scutellum of Triticum durum caryopses show different quiescence models: while epithelium cells display a DNA content per nucleus of 2C, the parenchyma cells undergo poli- ploidization. Furthermore, in old seeds, the distribution of the histones/DNA ratio shifts much more in parenchyma cells than in columnar epithelium cells. It may thus be concluded that different tissues of the same organ (scutellum) are affected in a different way by damaging effect of ageing factors