Degradation Of Protein Bodies Research Articles

Changes in some enzymes of microbodies and plastid development in excised radish cotyledons: Effect of narciclasine

Narciclasine (NCS), isolated from mucilage of Narcissus bulb, showed inhibitory effects on growth and plastid development of excised radish cotyledons. NCS (0.1 mumol/L) started to show inhibitory effects on isocitrate lyase and hydroxypyruvate reductase activities after 24 h incubation in light. When NCS concentration was increased to 10 mumol/L, the activities of both enzymes are completely inhibited. From ultrastructural studies, NCS markedly prevented the degradation of protein bodies and lipid bodies, as well as chloroplast formation of excised radish cotyledons. There was only little degradation of protein and lipid bodies, and almost no chloroplast formation in the excised radish cotyledon treated with 1 mumol/L NCS. Therefore, our results provide clear evidence that NCS inhibited the transition of glyoxysomes and peroxisomes, and chloroplast development.

Sugars as a metabolic regulator of storage protein mobilization in germinating seeds of yellow lupine (Lupinus luteus L.)

The intensity of protein reserve activation in yellow lupine (Lupinus luteus L.) organs cultured in vitro in the presence of saccharose and without sugar in the medium was studied. Isolated embryo axes, excised cotyledons and seeds deprived of their testae were grown on Heller medium: a) with 60 mM saccharose (+S), b) without sugar (−S) and c) for 72 hours without saccharose + for 24 hours in the presence of saccharose (−S→+S). Using nitroanilide substrates, exo- and endopeptidase proteolytic activity was investigated in enzymatic extracts. Proteolytic activity was examined in organs isolated from swollen seeds and also in organs cultured for 24, 48, 72 and 96 hours. The proteolytic activity was higher in organs cultured on medium without saccharose. Stimulation of the proteolytic activity on the first day of culture was not significant, but intensified in the successive days of culture. The organ subcultured onto a medium with saccharose (−S→+S) caused a significant limitation of proteolytic activity, even to a markedly lower level in comparison to that activity level in the material continuously supplemented with saccharose. Observations of ultrastructure in Transmission Electron Microscopy revealed increased protein body degradation in the absence of saccharose in the medium and an increased degree of cell vacuolization, which may be indicative of intensifying autophagic processes under conditions of carbohydrate deficit.

Sub-cellular immunolocalization of the glucosinolate sinigrin in seedlings of Brassica juncea.

Polyclonal rat antibodies were raised to a bovine serum albumin-sinigrin conjugate and used to immunolocalize sinigrin (2-propenylglucosinolate) in imbibed seeds and developing seedlings of Brassica juncea. (L.) Czern. Sinigrin was localized to protein bodies in aleurone-like cells but shown to be absent from myrosin cells. Double labelling techniques were used to co-localize both myrosinase (beta-thioglucoside glucohydrolase, EC 3.2.3.1) and sinigrin. Myrosin grains were labelled only with the anti-myrosinase antibody, but aleurone cells were labelled with both anti-myrosinase and anti-sinigrin antibodies. High-performance liquid chromatographic analysis of conventionally fixed and dehydrated seed tissues (4 h post imbibition in water), indicated a high proportion of sinigrin was retained in fixed tissues. Over a time course of 100 h, protein bodies within aleurone-like cells degraded, fused to form the cell vacuole and lost all myrosinase labelling but retained residual sinigrin labelling. The degradation of protein bodies corresponded to a decrease in retention of sinigrin in the fixed tissues. The results describe for the first time the co-localization of a plant enzyme and its substrate, a secondary metabolite.

Ultrastructure of Carrot Seeds during Matriconditioning with Micro-Cel E

Matriconditioning (MC) of carrot seeds, with Micro-Cel E, improved their germinability by shortening the mean germination time and reducing the spread. Cytological studies indicated that the catabolic phase of germinationsensu strictoadvanced during the 8 d period of MC, but that the observed changes differed in embryo and endosperm tissues. Complete degradation of storage protein and lipid bodies, followed by starch accumulation were found to occur in the embryonic radicles of carrot seeds. In the endosperm, the catabolic changes were restricted to the micropylar area enclosing the radicle, where extensive breakdown of storage cell walls, partial degradation of protein bodies and no storage lipid hydrolysis were noted. The time course and localization of these changes suggested that weakening of the endosperm represented a secondary effect of priming, which was probably controlled and stimulated by the metabolically advanced embryonic axis. The benefits of seed matriconditioning have been explained on the basis of the fine structure observations.

Phytochrome-induced structural changes and protein degradation prior to radicle protrusion in Datura ferox seeds

In Datura ferox L. seeds induced to germinate by the far-red light absorbing form of phytochrome (Pfr) and alternating temperatures, protein degradation started before radicle protrusion. Proteolysis was, however, restricted to the micropylar region of the endosperm in which the protein content decreased 51% by 48 h after red light treatment. There was no change during that time in the protein content of the rest of the endosperm or in the embryo. Light and electron microscopy preparations show the vacuolation of protein bodies along with other changes in cellular structure in the micropylar portion of the endosperm in seeds treated with red light (R). No changes were detected in the rest of the endosperm or in the micropylar portions of far-red light (FR) treated seeds. In the embryonic axes there were some alterations but only in a small sector of the calyptra. In contrast, shortly after radicle protrusion (5 h), there was extensive degradation of protein bodies in the embryonic axes. A Pfr is required for the induction of protein degradation in the micropylar portion of the endosperm in the intact seed before radicle protrusion. Incubation of isolated micropylar portions induced protein degradation in tissues from seeds treated with either R or FR. The results do not support a source–sink type of control of protein degradation in the endosperm driven by the beginning of embryo growth but suggest the participation of regulatory signals in the determination of a temporal and spatial pattern of protein degradation in both the endosperm and the embryo. Key words: germination, dormancy, phytochrome, protein degradation, micropylar endosperm.

Degradation of Protein and Lipid Bodies during Dormancy Removal in Apple Seeds

The cytological changes occurring in dormant embryo axial tissues of Malus domestica (Borb.) during 90 d of chilling (cold stratification of seeds at + 5 °C) as well as during 90 d of the warm control (+ 20 °C) were compared in order to discern those which are specifically related to dormancy release. It is supposed that storage protein bodies undergo degradation in two steps, 1) independent of the low temperature, involving partial hydrolysis of storage protein and 2) dependent on the low temperature, leading to the complete degradation of protein bodies. Degradation of lipids and their supposed interconversion into sugars (observed as accumulation of starch) are specifically linked with the low temperature treatment. Other observed cold-mediated changes include formation of the granular component in the enlarged nucleolus, rough ER, Golgi structures, development of amyloplasts and glyoxysomes. Disintegration of cellular membranes taking place under conditions of control warm treatment is discussed in relation to ageing.

Protein Body Degradation in the Starchy Endosperm of Germinating Sorghum

Protein Body Degradation in the Starchy Endosperm of Germinating Sorghum

Degradation of Protein Bodies in Germinating Seeds of Brassica campestris L. var. sarson Prain

Histochemical investigations were carried out on dry and germinating seeds of Brassica campestris var. sarson, to study the degradation of protein bodies with globoidal inclusions. During germination, a wave of protein body degradation sets in from the radicular end of the embryo, passing through the hypocotyl and shoot apex, and ending in the cotyledons. The digestion of protein bodies is of the internal type. The various isolated parts of the embryo showed a similar pattern of protein body digestion to that of the whole embryo, except that in some cells the globoids persisted even after complete digestion of protein bodies; the rate was faster in the comparatively more expanded part of the isolated organs. No specific factor controlling the initiation of the wave of protein body digestion could be ascertained.

ANATOMY, HISTOCHEMISTRY AND CYTOLOGY OF DORMANT AND STRATIFIED APPLE EMBRYOS

SUMMARYThe following sequence of structural changes which are related to the utilization of storage materials have been shown to occur in the apple embryo: degradation of protein bodies, degradation of lipid bodies, appearance and degradation of starch. These processes take place in the embryonic axis during stratification and in the cotyledons during the germination of stratified embryos. Important differences were observed in the localization of these processes during the early post‐embryonic (up to 12 days) growth of dormant and stratified embryos. It is concluded that during the germination of dormant embryos the embryonic axis influences certain hydrolytic processes in cotyledons by delaying and inhibiting their progress, whereas in non‐dormant embryos these are stimulated by the embryonic axis.

Welwitschia mirabilis: Fine Structure of the Germinating Seed IV. The Imbibed Gametophyte

Summary During the first two days after imbibition, in the cells of the gametophyte of Welwitschia, the volume of the nucleolus increases and membranes become clearly defined. Microbodies increase strikingly up to day 3, but decline in number after day 4 as lipid reserves are consumed. Microbodies, often containing spherical inclusions within an amorphous electron dense region near the enclosing membrane, and lipid bodies are sequestered into protein bodies. Digestion of protein body reserves begins from within the protein-carbohydrate deposits, giving the body a fenestrated appearance. Small, spherical, electron dense crystalline inclusions, presumably globoids, are found not only in the protein-carbohydrate deposits of the protein body, but also in contact with the outer protein body membrane as well as in the cytoplasm. This suggests a cytoplasmic origin for the globoid. Mitochondria, ER and ribosomes are numerous by day 4; amyloplasts, dictyosomes and myelin figures appear by day 5. By day 6 protein bodies fuse to form aqueous vacuoles, lipid reserves are depleted and amyloplasts are numerous. Although nuclear inclusions disappear upon imbibition nucleoli tend to remain in a semi-quiescent state; this, coupled with the pattern of protein body degradation, suggests an embryo-controlled mobilization of food reserves.

Changes in Paramagnetic Manganese (Mn(II)) and Related Enzyme Activities in Isolated Cucumber Cotyledons During Growth

Changes» in the activities of IAA oxidase, peroxidase, and ascorbic acid utilization (AAU) and in the level of paramagnetic manganese (Mn(II)) have been studied during GA3-induced growth of the isolated cucumber cotyledons in light or dark. In dark-grown cotyledons, where GA3 fails to evoke any growth response, an initial decline in the Mn(II) content during the first 8 h is followed by a rise which approaches the control value between 12 and 24 h. A marked, almost linear increase is observed in Mn(II) levels from 48 h onwards. The initial decline in Mn(II) is accompanied by an increase in IAA oxidase activity and decreased AAU. The large increases obtained at later times, viz. 48 and 72 h, appear to be related primarily to the release of manganese due to the degradation of protein bodies which proceeds under the action of GA and also to increased AAU. The IAA oxidase and peroxidase activities are close to control during this period. In light, however, IAA oxidase and peroxidase activities show marked increase during the first 4 h but no significant changes are observed in Mn(II) level or AAU. The peak of Mn(II) observed at 8 h corresponds with lower activities of IAA oxidase and peroxidase but an increase in AAU. The changes in Mn(II) closely correspond with the changes in AAU in light, peroxidase and IAA oxidase activities keeping close to the control. It appears that GA action is related to increased Mn(II) due to increased AAU which may be coupled to the peroxidase-IAA oxidase system. The study confirms the postulate given by us in an earlier paper.

Isoenzyme Activities during the Early Stages of Allium Radicle Germination

AbstractAs a continuation of a study of the molecular events surrounding the establishment of a mature root apex, changes in the pattern and specific activity of the isoenzymes of aminopeptidase (AmP), esterase (EST), glucose‐6‐phosphate de‐hydrogenase (G6PD) and glutamic‐oxaloacetic transaminase (GOT) were investigated during the early germinative growth of the Allium radicle tip.Polyacrylamide disc gel electrophoresis revealed a total of 9 EST fractions. A shift in pattern and reactivity characteristic of pre‐emergence to those characteristic of post‐emergence was demonstrated.G6PD electropherograms displayed 5 isoenzyme bands. Relative specific activity analyses indicated that this enzyme may be more important during the very early stages of germination.Only quantitative differences were noted in the 3 AmP isoenzymes detected. The progressive increase in AmP isoenzyme activity during the period of maximal protein body degradation suggested a role for these exopeptidases in the degradation of reserve proteins.The 3 isoenzyme bands of GOT exhibited only quantitative changes during germination. Parallel increases in the quantity of soluble protein and GOT specific activity suggest that this isoenzyme is involved in the onion's nitrogen metabolism during germination.