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Isolation of oligomers of 5,6-dihydroxyindole-2-carboxylic acid from the eye of the catfish.

ABSTRACT: The reflecting material of the tapetum lucidum of the sea catfish (Arius felis) was chromatographed on Sephadex LH-20 in methanol-dimethyl sulphoxide-formic acid. Two components were present: one, showing an absorption maximum at 330nm, was tapetal pigment; the other, at 257nm, was an associated nucleoside. The tapetal pigment was extracted in methanol-HCl and isolated by adsorption chromatography on Sephadex LH-20. It yielded a methoxy methyl ester on treatment with diazomethane, and permanganate oxidation gave pyrrole-2,3,5-tricarboxylic acid. From the information provided by u.v. and i.r. spectra of the pigment and its methoxy methyl ester, from elemental analyses and from the oxidation products, we suggest that the tapetal pigment is derived from oxidative coupling of 5,6-dihydroxyindole-2-carboxylic acid. A molecular-weight determination and chromatography of the methoxy methyl ester indicate that the pigment is a mixture of oligomers, among which the tetramers probably predominate. We consider that the monomers are joined mainly by C-C linkages at positions 4 and 7. A synthetic pigment having spectral properties nearly identical with those of the natural pigment was prepared by enzymic oxidation of 5,6-dihydroxyindole-2-carboxylic acid with mushroom tyrosinase. The identity of the tapetal pigment with the synthetic pigment was further confirmed by comparing u.v. and i.r. spectra of their methoxy methyl esters. Formation of the tapetal pigment from tyrosine and relationships of the tapetal pigment to melanin are discussed.

SUBMITTER: Ito S

PROVIDER: S-EPMC1168369 | biostudies-other | 1974 Oct

REPOSITORIES: biostudies-other

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Project description:Using microarray technology and a set of chickpea (Cicer arietinum L.) unigenes and grasspea (Lathyrus sativus L.) ESTs, chickpea responses to treatments with the defence signalling compounds salicylic acid (SA), methyl jasmonate (MeJA), and aminocyclopropane carboxylic acid (ACC) were studied in four chickpea genotypes with ranging levels of resistance to ascochyta blight (Ascochyta rabiei (Pass.) L.). The experimental system minimized environmental effects and was conducted in reference design, where samples from untreated controls acted as references against post-treatment samples. Robust data quality was achieved through the use of three biological replicates (including a dye-swap), the inclusion of negative controls, and strict selection criteria for differentially expressed genes including a fold change cut-off determined by self-to-self hybridizations, Students t test and multiple testing correction (P<0.05). Microarray observations were also validated by quantitative RT-PCR. The time-course expression patterns of 715 experimental microarray features resulted in differential expression of 425 genes in at least one condition. The A. rabiei resistant chickpea genotypes showed a more substantial range of defence-related gene induction by all treatments, indicating that they may possess stronger abilities to resist infection. Further, the involvement of SA, MeJA, and ACC signalling was identified for the regulation of some important A. rabiei responsive genes, as well as cross-talk between these pathways. This study also found evidence to suggest the involvement of A. rabiei-specific signalling mechanisms for the induction of several genes that were previously implicated in A. rabiei resistance. Overall, this study characterised the regulatory mechanisms of many chickpea genes that may be important in defence against various pathogens, as well as other cellular functions. Although the size of the microarray was limited, the results provided novel insights to the molecular control of chickpea cellular processes, which may assist the understanding of chickpea defence mechanisms and allow enhanced development of disease resistant cultivars. Keywords: time course defence-signalling teatment analysis

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Isolation of oligomers of 5,6-dihydroxyindole-2-carboxylic acid from the eye of the catfish.

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