Cotyledons Of Sinapis Alba Research Articles

Abstracts, Saskatchewan-Alberta Regional Meeting, The Canadian Phytopathological Society, 1998

Abstracts, Saskatchewan-Alberta Regional Meeting, The Canadian Phytopathological Society, 1998

WOUND-INDUCED ANTIXENOTIC RESISTANCE TO FLEA BEETLES, PHYLLOTRETA CRUCIFERAE (GOEZE) (COLEOPTERA: CHRYSOMELIDAE), IN CRUCIFERS

AbstractLaboratory experiments were conducted to determine the effect of wounding the cotyledons of Sinapis alba L. cv. Ochre, Brassica napus L. cv. Westar, B. rapa L. cv. Tobin, and C8711, a selection from Tobin, on subsequent feeding damage by the flea beetle, Phyllotreta cruciferae (Goeze). Cotyledons of 7-day-old seedlings were wounded either by puncturing them with needles (mechanical wounding) or by exposing them to flea beetles. One, 2, or 9 days following wounding, the wounded and unwounded seedlings were exposed to flea beetles and the feeding damage was estimated as a measure of antixenosis. Mechanical wounding of one of the cotyledons with 96 needle punctures induced a significant reduction in the damage of the unwounded cotyledons of S. alba, 1 or 2 days following wounding. True leaves of the wounded seedlings also showed consistently less damage than unwounded controls, 9 days following wounding. In S. alba, all three levels of mechanical wounding (i.e. 6, 24, or 96 punctures per cotyledon) reduced subsequent flea beetle damage to a similar extent. Wrapping a cotyledon of S. alba with a plastic film produced an effect similar to wounding it with needles. As with mechanical wounding, flea beetle wounding also reduced subsequent flea beetle damage in S. alba. Other plant species (B. napus and B. rapa) tested showed no measurable induced effects on subsequent feeding damage.

The molecular basis of the density increase of phenylalanine ammonia-lyase, extracted from the cotyledons of mustard (Sinapis alba) incubated on deuterium oxide

Abstract Previous studies of deuterium labelling of proteins have measured shifts in buoyant density and inferred the incorporation of deuterium into the free amino acids. This paper reports the use of combined gas-liquid chromatography-mass spectrometry to measure the incorporation of deuterium into the free amino acids of Sinapis alba cotyledons, from which the expected density shift of phenylalanine ammonia-lyase (EC 4.3.1.5) has been calculated and compared with that measured by isopycnic density-gradient centrifugation. The quantitative results show that most of the amino acids entering phenylalanine ammonia-lyase are only deuterated to a small extent and pass from storage protein to phenylalamine ammonia-lyase virtually without engaging in enzyme-catalysed exchange reactions. Most of the deuterium incorporated into phenylalanine ammonia-lyase is transferred with the amino acids alanine (approx. 32%), glutamate (approx. 21%), and glutamine (approx. 16%). Possible reasons for the discrepancy between the calculated and observed shift in buoyant density of phenylalanine ammonia-lyase are discussed.

Obtention d'épinastie des cotylédons de Sinapis alba en éclairement rouge Iointain continu.

Abstract Obtention of epinasty in the cotyledons of Sinapis alba under continuous far‐red illumination. Relation to the development of hypocotyl and cotyledons. Treatment by far red light induces epinasty of the cotyledonary leaf. The effects of light treatments of different intensities were recorded for hypocotyl length, percentage of epinasty and the cotyledon leaf area. The percentage of epinasty increases as a function of treatment duration and light intensity. As from the second day of treatment a correlation is obtained between the percentage of epinasty and hypocotyl length when the seedlings are given far‐red light treatment of different durations.

Formation of protein storage bodies during embryogenesis in cotyledons of Sinapis alba L.

An electron microscopic investigation of fine structural changes in post-meristematic cotyledon mesophyll cells during the period of storage protein accumulation (16-32 d after pollination) showed that the rough ER, the Golgi apparatus and the developing vacuome are intimately involved in the formation of storage protein bodies (aleurone bodies). At the onset of storage protein accumulation (16-18 d after pollination) storage protein-like material appears within Golgi vesicles and preformed vacuoles. At a later stage (24 d after pollination) similar material can also be detected within vesicles formed directly by the rough endoplasmic reticulum (ER). It is concluded that there are two routes for storage protein transport from its site of synthesis at the ER to its site of accumulation in the vacuome. The first route involves the participation of dictyosomes while the second route bypasses the Golgi apparatus. It appears that the normal pathways of membrane flow in the development of central vacuoles in post-meristematic cells are used to deposit the storage protein within the protein bodies. Thus, the protein body can be regarded as a transient stage in the process of vacuome development of these storage cells.

Phytochrome control of amino acid synthesis in cotyledons of Sinapis alba

Continuous far red light, acting through phytochrome, stimulates the rate of incorporation of density label into amino acids in the cotyledons of Sinapis alba. It is shown that such stimulation leads to increased incorporation of label into proteins. This has important consequences for experiments in which rates of enzyme synthesis in light treated and dark grown plants are compared by labelling methods. The results of some such experiments are re-evaluated.

Formation of oleosomes (storage lipid bodies) during embryogenesis and their breakdown during seedling development in cotyledons of Sinapis alba L.

Electron microscopic and biochemical investigations of developing embryonic mustard cotyledons provided no evidence for the widely accepted hypothesis that oleosomes of fat-storing tissues originate from the endoplasmic reticulum and are surrounded by a unit- or half-unit membrane. In contrast, it was found that the first lipid droplets appear (about 12-14 d after pollination) in the ground cytoplasm near the surface of plastids. Subsequently these nascent lipid droplets, which lack any detectable boundary structure at this stage, become encircled by a cisterna of rough endoplasmic reticulum. At the same time an osmiophilic coat of about 3 nm thickness becomes detectable at the lipid/water interface. In the cotyledon cells of germinating seedlings a centrifugally moving front of fat degradation moves from the central vacuoles(s) towards the cell periphery, leaving behind collapsed coats of oleosomes which are depleted of their lipid contents (saccules). Although saccules appear tripartite in cross section, they are structurally different from endoplasmic reticulum membranes. The oleosome coats can be isolated from oleosome preparations by extracting lipids with organic solvents. The coat material is insoluble in detergents like Triton X-100 or deoxycholate and shows a tripartite, lamellar structure (similar to collapsed saccules) under the electron microscope. Upon dissolution with dodecylsulfate, polyacrylamide gel electrophoresis revealed a polypeptide composition (9 major bands) which is qualitatively different from that of the endoplasmic reticulum membrane. Also the buoyant densities of defatted oleosome coats and defatted endoplasmic reticulum membranes are very different. It is concluded that oleosome lipids accumulate in the ground cytoplasm and are bounded by a lamellar structure originating de novo from proteinaceous elements synthesized by specific regions of the endoplasmic reticulum.

Pattern formation underlying phytochrome-mediated anthocyanin synthesis in the cotyledons ofSinapis alba L.

The ability to respond to phytochrome (Pfr, the far-red light absorbing from of phytochrome) with anthocyanin synthesis appears first in some marginal regions of the abaxial epidermis of the mustard cotyledons and from there spreads gradually over the entire tissue (transient phase). The pertinent pattern is independent of environmental influences such as light quality and nutritional culture conditions. The competence for Pfr in the epidermal cells, with regard to the initial action of Pfr (concerning anthocyanin synthesis), appears considerably earlier than the ability for actual anthocyanin synthesis. An electron microscopical study of the ultrastructural changes occurring in vacuoles and plastids of the epidermal cells during the transient phase showed that a correlation only exists between the differentiation of central cell vacuoles, originating from the aleurone vacuoles, and the appearance of the ability to accumulate anthocyanin. It is suggested that the formation of a central cell vacuole is a prerequisite for anthocyanin accumulation in the epidermal cells of the mustard seedling cotyledons.

The capacity of chlorophyll-a biosynthesis in the mustard seedling cotyledons as modulated by phytochrome and circadian rhythmicity

Within the temporal pattern of "primary differentiation" the capacity of chlorophyll - a biosynthesis in the cotyledons ofSinapis alba L. seedlings is controlled by phytochrome (in continuous light) or by releasing the circadian rhythm either with lightdark cycles or by a light→dark transition. The sensor pigment for this process is phytochrome. It is very probable that in continuous light as well as under conditions under which the circadian rhythm plays the major part, the capacity of chlorophyll a biosynthesis is limited by the capacity of the biosynthetic step which produces 5-aminolaevulinate.

Light control of plastogenesis and ribulosebisphosphate carboxylase levels in mustard seedling cotyledons

We have studied the problem whether the phytochrome-mediated accumulation of ribulosebisphosphate carboxylase ("carboxylase"; EC 4.1.1.39) in the cotyledons of sinapis alba L. is related to size, ultrastructure, or organization of the plastid compartment. We have shown that under different light conditions (e.g. continuous far-red light, continuous white light) which lead to conspicuously different plastids the time course of the enzyme levels remains precisely the same. It is concluded that the onset and the rate of carboxylase accumulation is not related to the organizational state of the plastid compartment as discernible under the electron microscope.

Rapid activation by phytochrome of nitrate reductase in the cotyledons of Sinapis alba

Nitrate reductase in the cotyledons of etiolated seedlings of Sinapis alba L. responds rapidly to the addition of nitrate. The response is inhibited by cycloheximide at low concentrations. The enzyme is also under phytochrome control. Five minutes of red light irradiation leads instantaneously to a 45% increase in enzyme activity. Increases in activity, linear with respect to time and with no lag phases are promoted by continuous far-red or blue irradiation. These increases are insensitive to cycloheximide. Thus, light and nitrate act through different mechanisms in controlling nitrate reductase activity and phytochrome does not act via controlling the rate of synthesis of the enzyme.

The appearance of competence for phytochrome-mediated anthocyanin synthesis in the cotyledons of Sinapis alba L.

It is demonstrated that phytochrome-mediated anthocyanin synthesis in the epidermal cells of mustard seedling cotyledons takes place only 27 h after sowing onwards (at 25°C). This "starting point" cannot be shifted by light treatments or by nutrients. The late appearance of competence for P fr (P r and P fr, red- and far-red absorbing forms of phytochrome, respectively) with regard to anthocyanin synthesis is not related to the phytochrome system per se (P r⇆P fr) as this is fully functional immediately after sowing of the seed; nor is it related to the primary reaction of phytochrome: P fr+X→P fr X→P fr X' (X, X', two forms of a receptor for P fr) or to the initial action of P fr X':P fr X'+K'→Y' (K', coupling element, leading to the product Y', which is no longer photoreversible). Rather, the "starting point" is determined by internal factors only and is thus not accessible to any specific control by external factors. On the other hand, however, the beginning of the initial action of P fr X' ("coupling point") can be shifted by light via phytochrome under high irradiance conditions. Moreover, it is shown that there is no phytochrome-independent effect of blue light on photomorphogenesis in the young mustard seedling and that there is no "rapid dark reversion of P fr" which can be detected by physiological means, at least during.

The Effects of Temperature on Root Initiation in Detached Cotyledons of Sinapis alba L.

The Effects of Temperature on Root Initiation in Detached Cotyledons of Sinapis alba L.

Inhibitor-dependent, reciprocal changes in the activities of glyceraldehyde 3-phosphate dehydrogenases in Sinapis alba cotyledons

Summary Glyceraldehyde 3-phosphate dehydrogenases (GPD) from cotyledons of far-red- light-grown Sinapis alba seedlings can be separated by ammonium sulfate chromatography into two enzymes designated NAD-GPD I and NADP-GPD • NAD-GPD II. The former species is probably the NAD-GPD of cytoplasmic glycolysis (EC 1.2.1.12). The latter species has both NADP and NAD activity and is apparently identical to the NADP-GPD of plastids (EC 1.2.1.13). When puromycin (100 μg • ml-1) or D-threo chloramphenicol (200 μg • ml-1) is applied to seedlings, the light-dependent increase in the activities of the bifunctional enzyme is strongly inhibited. The resultant decrease in NAD-GPD II activity of this enzyme is accompanied by an equivalent increase in NAD-GPD I activity. The application of actinomycin D (10 μg • ml-1) affects neither of these two enzymes, but significantly inhibits the activity increase of the control enzyme glyoxylic acid reductase (EC 1.1.1.26). These and other regulatory data published previously are discussed on the basis of a model proposing that the formation of glyceraldehyde 3-phosphate dehydrogenases proceeds sequentially via an anabolic pathway in which the glycolytic enzyme of the cytoplasm functions as a precursor or subunit of the bifunctional chloroplast enzyme.

The Effect of Sucrose on Primordium Development and on Protein and RNA Levels in Detached Cotyledons of Sinapis alba L.

The Effect of Sucrose on Primordium Development and on Protein and RNA Levels in Detached Cotyledons of Sinapis alba L.

The development of protein and oil bodies in the seed of Sinapis alba L.

The cotyledons of Sinapis alba L. seed are the storage organs and first photosynthetic organs. The development of the cotyledon cell contents was studied using electron and light microscopy. From the heart shaped embryo (11 days from petal fall) to the mature seed, nine stages were examined.Both types of protein grains (designated aleurone grains and myrosin grains) were found to form within vacuoles, but the mode of protein accumulation differed with each type of grain.Oil bodies were apparent with the EM from 18 days onwards, but could not be seen to arise from the ER. They were granular in appearance at early stages, but later became electron transparent.

The Control of Root Initiation and Development in Detached Cotyledons of Sinapis alba L. and Raphanus sativus L.

The Control of Root Initiation and Development in Detached Cotyledons of Sinapis alba L. and Raphanus sativus L.

The effects of light and cotyledon age on growth and root formation in excised cotyledons of Sinapis alba L.

Root formation on excised mustard cotyledons was found to be determined by cotyledon age at excision and by light. Light treatment after excision enhanced root production in cotyledons excised 6 hours to 6 days after the start of imbibition and was essential for root production in cotyledons older than 6 days at excision. Three or more 12 hour light periods after excision were sufficient to induce root production in almost 100% of 7 day old cotyledons. The interposition of up to 5 days of darkness between excision and subsequent culture in the light did not reduce the final rooting percentage but delayed the onset of rooting by a time equivalent to the length of the dark period. The dry weight values of the cotyledons were directly related to the total light energy received after excision.The age and light effects on rooting may be mediated by their effects on the rate of breakdown and on the total levels of available reserves present in the cotyledons.