The synthesis of acetylcholine by plants | Biochemical …
The betaine biosynthesis pathway of betaine-accumulating plants involves choline ..
Methylation by plant and animal tissues. 4. Choline synthesis.
Although it had been thought that betaine synthesis is well regulated to protect plant against abiotic stress, here it is shown that an exogenous supply of precursors such as choline, serine, and glycine in the betaine-accumulating plant further enhances the accumulation of betaine under salt-stress, but not normal, conditions.
The abiotic stresses due to temperature, drought, and salinity are collectively also known as water deficit stresses. The plants produce osmolytes or osmoprotectants to overcome the osmotic stress. The attempts are on to use genetic engineering strategies to increase the production of osmoprotectants in the plants. The biosynthetic pathways for the production of many osmoprotectants have been established and genes coding the key enzymes have been isolated. E.g. Glycine betaine is a cellular osmolyte which is produced by the participation of a number of key enzymes like choline dehydrogenase, choline monooxygenase etc. The choline oxidase gene from Arthrobacter sp. was used to produce transgenic rice with high levels of glycine betaine giving tolerance against water deficit stress.
Scientists also developed cold-tolerant genes (around 20) in Arabidopsis when this plant was gradually exposed to slowly declining temperature. By introducing the coordinating gene (it encodes a protein which acts as transcription factor for regulating the expression of cold tolerant genes), expression of cold tolerant genes was triggered giving protection to the plants against the cold temperatures.
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Moreover, our results suggest that higher Cho contents might be achieved by further engineering. One approach would be to introduce a truncated PEAMT () that is less sensitive to inhibition by phosphocholine, as proposed (). However, it is doubtful that this maneuver in itself would be optimal, for analysis of the pools of Cho synthesis intermediates and the effect of supplying EA indicate that PEAMT+ plants suffer from an inadequate internal EA supply. The EA-feeding experiments further suggest that this supply depends on the rate of EA degradation as well as synthesis. Both these processes could in principle be engineered to make more EA available for Cho production.
Choline monooxygenase catalyzes the oxidation of choline to betainealdehyde which is a key enzyme for the betaine synthesis in plants. Purified CMO showed extremely low activity probably due to the labile property of the enzyme. For functional characterization of CMO, we constructed the vectors in which the CDH gene of gene clusters was replaced with CMO or deleted, and used for the transformation of (DH5a) and fresh water cyanobacterium PCC7942, neither of which could synthesis betaine. We found that E. coli cells in which choline dehydrogenase (CDH) was replaced with spinach CMO accumulate betaine. Changes of Cys181 in spinach CMO to Ser, Thr, and Ala and His287 to Gly, Val, and Ala abolished the accumulation of betaine. Overexpression of spinach CMO in , and conferred resistance to abiotic stress. These results will be presented.
Differences Between Omega-3 Fats From Plants and …
Choline (Cho) is the precursor of the osmoprotectant glycine betaine and is itself an essential nutrient for humans. Metabolic engineering of Cho biosynthesis in plants could therefore enhance both their resistance to osmotic stresses (drought and salinity) and their nutritional value. The key enzyme of the plant Cho-synthesis pathway is phosphoethanolamine N-methyltransferase, which catalyzes all three of the methylations required to convert phosphoethanolamine to phosphocholine. We show here that overexpressing this enzyme in transgenic tobacco increased the levels of phosphocholine by 5-fold and free Cho by 50-fold without affecting phosphatidylcholine content or growth. Moreover, the expanded Cho pool led to a 30-fold increase in synthesis of glycine betaine via an engineered glycine betaine pathway. Supplying the transgenics with the Cho precursor ethanolamine (EA) further enhanced Cho levels even though the supplied EA was extensively catabolized. These latter results establish that there is further scope for improving Cho synthesis by engineering an increased endogenous supply of EA and suggest that this could be achieved by enhancing EA synthesis and/or by suppressing its degradation.
In previous work, a chloroplastic GlyBet synthesis pathway was inserted into tobacco (which lacks GlyBet) by expressing spinach choline monooxygenase (CMO).
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Choline - Wikipedia
10/01/2018 · Request (PDF) | The synthesis of ace..
Choline / ˈ k oʊ l iː n / is a water-soluble vitamin-like essential nutrient
PHOSPHATIDIC ACID PHOSPHOHYDROLASE1 and 2 …
Acetylcholine - Wikipedia
plants has been reported to increase choline …
In plants, S-adenosyl-L-methionine-dependent phospho-base N-methyl transferases catalyze the three sequential methylations of phosphoethanolamine to phosphocholine, the precursor for choline and the major membrane phospholipid phosphatidylcholine. The enzyme phosphoethanolamine N-methyltransferase (PEAMT) catalyzes the first and committing step in choline synthesis, a step for which no known by-pass has been found. In Arabidopsis thaliana there are two loci annotated as encoding PEAMT and a putative PEAMT, At3g18000 (NMT1) and At1g73600 (NMT3), respectively. A related gene product that catalyzes the last two methylations is encoded by locus At1g48600 (NMT2). The objective of this study was to investigate the role of NMT3 in Arabidopsis. Three SALK lines carrying independent T-DNA insertions in At1g73600 were used: SALK_062703, SALK_016929c and SALK_120703c.
01/04/2014 · Abstract
NMT3 was the most highly expressed of the three NMT genes monitored by q-PCR. Nonetheless, three independent T-DNA insertion lines defective for NMT3 expression were wild-type by appearance and as such, offer compelling evidence that NMT3 is not required by Arabidopsis. The increased expression of NMT1 in nmt3 plants and NMT3 in nmt1 plants strongly suggests that plants compensate for the loss of one gene by up-regulating, to varying extents, the expression of the remaining NMT gene. If this is the case, a reasonable prediction made for a cross between nmt1 and nmt3 plants is that it would be lethal unless plants have yet another way to circumvent the loss of an essential enzyme for this committing metabolic bottleneck in choline synthesis.
Choline Synthesis in Spinach in Relation to Salt Stress
Serotonin is an indolamine monoamine neurotransmitter. The synthetic pathway is analogous to the catecholamines in many ways. An important distinction is that the rate limiting step is the uptake of tryptophan into the neuron. Tryptophan availability is the actual rate limiting factor in the intact animal. Tryptophan crosses the blood brain barrier via an active transport mechanism in competetion with other neutral amino acids such as leucine, lysine, and methionine. The activity of this transport mechanism is facilitated by the presence of insulin and glucose. Another interesting aspect of this system is the fact that tryptophan is one of the few amino acids which is bound in the plasma to any significant degree. The actual binding site is the fatty acid binding site of the albumen. This system allows a multitude of factors to ultimately influence the rate limiting step in serotonin synthesis. For example anything which increases free fatty acids would displace the tryptophan and thus increase the percent free which is able to cross the BBB. An example of such events include any acute stressor which increases glucocorticoid response, exercise, and acute alcohol consumption.
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