The effect of temperature and light on the accumulation of homoserine in pea seedlings

Grant, D.R.; Voelkert, E.

doi:10.1016/s0031-9422(00)85216-4

Cited by 6 publications

(1 citation statement)

References 9 publications

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“…Preliminary experiments showed that continuous light increased the total levels of homoserine in intact plants (shoots 4-fold, roots 2-fold increase in 2 d). This was in contrast to the observation that in young etiolated seedlings, light decreased the levels of homoserine (2). Stimulation by light was also found in detached shoots, confirming that synthesis was not restricted to roots, and Table I shows the homoserine content of individual leaves from shoots given different light regimes.…”

Section: Resultsmentioning

confidence: 60%

The Role of Transamination in the Synthesis of Homoserine in Peas

Joy¹,

Prabha²

1986

Plant Physiol.

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ABSTRACIÌ ncubation of intact pea plants (Pisum sativum), or detached shoots, in continuous light caused a substantial increase (up to 4-fold in 2 days) in levels of homoserine. Amino acids supplied to leaves in the transpiration stream enhanced the accumulation, with glutamate, aspartate, and asparagine causing similar enhancement. Aminooxyacetate (AOA), a transamination inhibitor, at 1 millimolar prevented the accumulation. '4C-labeling experiments showed that succinate was a good source of carbon for homoserine synthesis; carbon from aspartate or asparagine was also incorporated into homoserine. For each precursor, the transfer of label was prevented by AOA. The keto acid analog of homoserine was rapidly transaminated in leaves to give homoserine. The results suggest that accumulating homoserine is synthesised by transamination rather than being derived from aspartate via the aspartate kinase/homoserine dehydrogenase pathway. The latter pathway was shown to be operating in the chloroplasts, and was sensitive to threonine (but was not inhibited by AOA), suggesting that this path has a role in synthesis of aspartatederived amino acids but is not involved in the accumulation of excess homoserine in the pea.Although homoserine is undetectable in most plants, it is thought to be an essential intermediate in the synthesis of threonine and methionine, and is considered to be derived from aspartate by the action of aspartate kinase, aspartyl semi-aldehyde dehydrogenase and homoserine dehydrogenase (9). In the leaf, this activity is located in the chloroplasts, including those of pea (1 1, 18). The pathway appears to be tightly regulated by threonine and lysine (9). In some plants such as the pea and Lathyrus (5), homoserine is present at quite high levels. It is particularly prominent during germination (4, 6), and may have a role as a transport compound. Kinetic properties of enzymes of homoserine metabolism in the pea and nonaccumulating species have been compared, but results did not provide a convincing explanation for homoserine accumulation (17).In our investigations of asparagine metabolism in the pea, several observations have suggested that homoserine was not directly derived from aspartate. There was a flow of nitrogen from the amino group of asparagine to homoserine, and this transfer was sensitive to the transamination inhibitor aminooxyacetate (15). In double labeling experiments, aspartate received considerable amounts of carbon and nitrogen from asparagine, whereas homoserine received mainly nitrogen (15). The deamidation inhibitor 5-diazo-4-oxo L-norvaline drastically inhibited production ofaspartate from asparagine, but had much less effect on transfer of nitrogen to homoserine (16). '5N-labeled alanine, asparagine, aspartate and glutamate were all effective as a source of nitrogen for homoserine synthesis (TC Ta, KW Joy, unpublished data). These results suggest a transfer of nitrogen to homoserine by transamination. Labeling experiments by other workers are also consistent with derivation of carbon,...

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Section: Resultsmentioning

confidence: 60%

The Role of Transamination in the Synthesis of Homoserine in Peas

Joy¹,

Prabha²

1986

Plant Physiol.

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Microbial metabolism of quorum-sensing molecules acyl-homoserine lactones, γ-heptalactone and other lactones

Safari

Amache

Esmaeilishirazifard

et al. 2014

Appl Microbiol Biotechnol

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The cell-to-cell communication of microorganisms is known to be via exertion of certain chemical compounds (signal molecules) and is referred to as quorum sensing (QS). QS phenomenon is widespread in microbial communities. Several Gram-positive and Gram-negative bacteria and fungi use lactone-containing compounds (e.g. acyl-homoserine lactones (AHLs), γ-heptalactone, butyrolactone-I) as signalling molecules. The ability of microorganisms to metabolise these compounds and the mechanisms they employ for this purpose are not clearly understood. Many studies, however, have focused on identifying AHL and other lactone-degrading enzymes produced by bacteria and fungi. Various strains that are able to utilise these signalling molecules as carbon and energy sources have also been isolated. In addition, several reports have provided evidence on the involvement of lactones and lactone-degrading enzymes in numerous biological functions. These studies, although focused on processes other than metabolism of lactone signalling molecules, still provide insights into further understanding of the mechanisms employed by various microorganisms to metabolise the QS compounds. In this review, we consider conceivable microbial strategies to metabolise AHL and other lactone-containing signalling molecules such as γ-heptalactones.

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Homoserine in seedlings of the tribe vicieae of the leguminosae

Lawrence

1973

Phytochemistry

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The effect of temperature and light on the accumulation of homoserine in pea seedlings

Cited by 6 publications

References 9 publications

The Role of Transamination in the Synthesis of Homoserine in Peas

The Role of Transamination in the Synthesis of Homoserine in Peas

Microbial metabolism of quorum-sensing molecules acyl-homoserine lactones, γ-heptalactone and other lactones

Homoserine in seedlings of the tribe vicieae of the leguminosae

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