Developing cotyledon

Millichip, M. et al.. Purification and characterization of oil-bodies (oleosomes) and oil-body boundary proteins (oleosins) from the developing cotyledons of sunflower (Helianthus annuus L.), Biochem. J., 314, 333, 1996. 

In M. guttatus, pea and maize, these genes appear to be expressed in a root-specific pattern. Levels of transcript are barely detectable in leaves, developing cotyledon, pith, seed and anther (de Miranda et al., 1990 Evans et al., 1990 de Framond, 1991). However, the soybean gene is expressed constitutively in both roots and leaves (Kawashima et al., 1991). 

Several cDNA clones encoding two different ADPGlc PPase polypeptides have been isolated from a cotyledonary library of V faba L.125 Sequences of the cDNAs were closely related to the ADPGlc PPase small subunit of other plants. One polypeptide is expressed in developing cotyledons and leaves, while the other is found solely in cotyledons. Crude extracts were assayed for ADPGlc PPase activity, and it was found that the enzyme from cotyledons is not activated by 3PGA, whereas the leaf enzyme was activated more than 5-fold. Pi inhibited both enzymes. These experiments were performed in the pyrophos-phorolysis direction. Whether 3PGA could reverse Pi inhibition was not studied.125... 

When developing cotyledons of soybean are supplied with [ C]acetate or with (Singh and Privett, 1969), APE becomes by far the most labeled compound. Nothing further is known about the pathway of acylation. Is PE the immediate precursor What is the acyl donor ... 

At stage A the embryo contains all the GAs found at stage B, and their amount is very similar. As far as dependence on the suspensor is concerned, we suspect, but cannot prove, that these GAs are provided by the suspensor. It is clear that developing cotyledons from 16 mm seeds [38] have acquired the ability to biosynthesize their own GAs. However whether this ability exists in the embryo since the first division of the zygote, or is acquired later, still needs to be clarified. 

The ammonium salt of [ CJlinoleic (9,12 octadecadienoic, 18 2) acid was converted into radioactive ciepenynic acid (18 1 A) by detached developing cotyledons of Crepis alpina, thus demonstrating that the formation of the acetylenic bond occurs via substraction of two hydrogen atoms from a A12 double bond. 

Since the precursor fatty acid (18 2) for 18 1 A formation is likely to be formed from oleoyl-phosphatidylcholine in the E.R. (Stymne and Appelqvist, 1978), it is reasonable to assume that the acetylenase is localized outside of the plastids, and perhaps in the E.R. itself. Therefore, microsomal preparations from developing cotyledons of Crepis alpina seeds were tested for their ability to convert [ " C]18 2 into [ C] 18 1 A. Microsomes from homogenate prepared in the presence of high amount of NADH were active in converting [14C]18 2-CoA into [14C]18 1-A. 

TABLE 1. Cofactor requirement and effects of carbon monoxide, anti-cytochrome-b antibodies and KCN on A12 desaturase and A12 acetylenase activities in microsomal preparations from developing cotyledons of Crepis alpina... 

Griffiths, G., Stobart, A.K. and Stymne, S. (1985) The acylation of 5/i-glycerol 3-phosphate and the metabolism of phosphatidate in microsomal preparations from the developing cotyledons of safflower (Carthamus tinctorius L.) seed. Biochem. J. 230, 379-388. 

Griffiths, G, Stobart, A. K. Stymne, S delta 6- and delta 12-desaturase activities and phosphatidic acid formation in microsomal preparations from the developing cotyledons of common borage (Borago officinalis). Biochem J1988, 252 641-647. 

Fig. 3.7. The cardinal events in seed maturation of Pisum spp. The common time scale is the growth curve for seed fresh weight. All events depicted refer to rates within the developing cotyledons, divergent lines denoting periods of increasing rate, convergent lines times of decreasing rate. Differences between P. sativum and P. arvense are indicated. After Pate, 1975 [13]...

The protein-synthesizing system of the developing cotyledon has itself been the subject for study in a number of laboratories. Cell-free protein-synthesizing systems have been obtained and polysomal (using native mRNA) and ribosomal (using synthetic messages, i.e. polyuridylic acid) activities determined at different stages of development. Attempts have also been made to link in vivo polysomal... 

LIPID SYNTHESIS IN DEVELOPING COTYLEDONS OF LINOLENIC ACID DEFICIENT MUTANTS OF LINSEED... 

In order to elucidate the mechanisms of alpha- linolenic acid synthesis in oil-seeds we have studied the biosynthesis and occurence of this acid in developing cotyledons of the high linolenic linseed (cv. Gleneig) and the linolenic acid deficient mutants, M1589, M1722 and Zero" derived from this variety. 

Table I. Distribution of M C] acyl groups in the sn-positions of phosphatidylcholine after [ C]linoleate feeding in-vivo to developing cotyledons. 17 DAP. The results are means of two incubations.

Table 2. Positional distribution of endogenous fatty acids in phosphatidylcholine from developing cotyledons, 17 DAP...

Table 3 In-vitro desaturation of endogenous oleate and linoleate at the different sn-positions of sn-phoshatidylcholine by homogenates of developing cotyledons.

Table 2. GLA utilisation in the developing cotyledons of linseed A. In total-lipid fatty acids...

Chroboczek et al. (1980), studying translation of plant viral RNA in the wheat germ system, found that, in the presence of mRNA from developing cotyledons of Vida faba, translation of nonstructural BMV mRNAs is arrested, while synthesis of BMV coat protein is only slightly inhibited. Similarly, synthesis of nonstructural polypeptides on tobacco mosaic virus RNA is arrested when Vida mRNA is added. It seems that mRNA for seed storage proteins is able to out-... 

TRIACYLGLYCEROL BIOSYNTHESIS IN DEVELOPING COTYLEDONS OF SAFFLOWER (Carthamus tincton us)... 

Developing cotyledons were excised from greenhouse-grown soybean plants. One cotyledon was placed in the medium containing San 9785 (100 urn) and the other cultured in the control solution without San 9785. These cotyledons were collected after two weeks in culture and then lyophlllzed. Neutral lipids from the cotyledons were extracted with petroleum ether. 

These hypotheses were examined by characterizing the selectivity of CPT and DAGAT in microsomal preparations from developing cotyledons of a series of oilseed plants towards different DAG species. Four different plants were used as model systems safflower (Carthamus tinctorius), a plant producing no unusual fatty acids rapeseed (Brassica napus), which stores erucic acid (22 1) in its TAG species Cuphea, a plant accumulating medium chain fatty acids (C8 - C12) in its seed triacylglycerols and castor bean (Ricinus communis) which stores up to 90% ricinoleic acid (18 1-OH) in its seed oils. 

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