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Molecular basis of quorum sensing signal-response systems in bacteria

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Ziemichod A., Skotarczak B.

Acta Biologica

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2017

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tom 24

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Quenching of acyl-homoserine lactone-dependent quorum sensing by enzymatic disruption of signal molecules

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Czajkowski R., Jafra S.

Acta Biochimica Polonica

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2009

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tom 56

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nr 1

1-16

Many Gram-positive and Gram-negative bacteria communicate using small diffusible signal molecules called autoinducers. This process, known as quorum sensing (QS), links cell density to the expression of genes as diverse as those associated with virulence factors production of plant and animal pathogens, bioluminescence, antibiotic production, sporulation or biofilm formation. In Gram-negative bacteria, this communication is mainly mediated by N-acyl-homoserine lactones (AHLs). It has been proven that inactivation of the signal molecules attenuates many of the processes controlled by QS. Enzymatic degradation of the signal molecules has been amply described. Two main classes of AHL-inactivating enzymes were identified: AHL lactonases which hydrolyse the lactone ring in AHLs, and AHL acylases (syn. AHL amidases) which liberate a free homoserine lactone and a fatty acid. Recently, AHL oxidoreductase, a novel type of AHL inactivating enzyme, was described. The activity of these enzymes results in silencing the QS-regulated processes, as degradation products cannot act as signal molecules. The ability to inactivate AHL (quorum quenching, QQ) might be useful in controlling virulence of many pathogenic bacteria.

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The accumulation of SA- and JA-signaling pathways in the response of Glycine max cv. “Nam Dan” to infestation by Aphis craccivora

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Tran N. T., Tran T. T. H., Do N. D., Mai V. C.

Journal of Plant Protection Research

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2017

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tom 57

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nr 4

Phytohormones function as signal molecules that regulate physiological processes to protect plants from environmental stresses, including aphids’ attack. We studied the pattern within the defense mechanisms of soybean [Glycine max (L.) Merr. cv. “Nam Dan”] regarding the signaling pathways of salicylic acid (SA), and jasmonic acid (JA) in response to cowpea aphid (Aphis craccivora Koch). With infestation by cowpea aphid, SA was the first to accumulate and reached high levels 24 hours post-infestation (hpi). An accumulation of SA in the early response of soybean probably triggers inducible specific defense reactions. Following SA, JA was later induced and continuously increased to high levels 96 hpi. An accumulation of JA in the later response may be a critical step in the signaling of the downstream defense cascade. In addition, phenylalanine ammonia-lyase (PAL, EC 4.3.1.24) and benzoic acid 2-hydroylase (BA2H), enzymes involved in the biosynthesis of SA, and lipoxygenase (LOX, EC 1.13.11.12), an important enzyme in the JA biosynthesis pathway, were also induced by cowpea aphid. The changes in the enzymatic activity of PAL, BA2H and LOX, and expression of gene encoding PAL were closely associated with the accumulation of endogenous SA and JA, respectively. The variations in the levels of these defense-related compounds were strongly connected with density and the duration of cowpea aphid infestation. Different accumulations of SA- and JA-signaling pathways may contribute to a coordinated regulation leading to the formation of resistant lines in the defense mechanisms of G. max cv. “Nam Dan” against A. craccivora.

Ograniczanie wyników

1 Acta Biochimica Polonica

1 Acta Biologica

1 Journal of Plant Protection Research

1 Czajkowski R.

1 Do N. D.

1 Jafra S.

1 Mai V. C.

1 Skotarczak B.

1 Tran N. T.

1 Tran T. T. H.

1 Ziemichod A.

2 2017

1 2009

Molecular basis of quorum sensing signal-response systems in bacteria

Quenching of acyl-homoserine lactone-dependent quorum sensing by enzymatic disruption of signal molecules

The accumulation of SA- and JA-signaling pathways in the response of Glycine max cv. “Nam Dan” to infestation by Aphis craccivora