Photobiochemistry without Light: Intracellular Generation and Transfer of Electronic Energy

Cilento, Giuseppe

doi:10.1007/978-1-4613-0709-9_27

Cited by 4 publications

(3 citation statements)

References 33 publications

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“…Cilento proposed that the excited-state species generated as products of certain enzymatic reactions were capable of transferring excitation energy to other molecules such as chlorophyll and xanthene dyes. This indicates that it has a photochemistry mode and a photobiology mode in mode of action [ 37 , 38 , 39 , 40 ]. In addition, α -terthienyl can exert toxic effects when in the absence of light, and it has some activity on plants and nematodes [ 41 ].…”

Section: Discussionmentioning

confidence: 99%

Transketolase Is Identified as a Target of Herbicidal Substance α-Terthienyl by Proteomics

Zhao

Huo

Liu

et al. 2018

Toxins

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α-terthienyl is a natural phytotoxin isolated originally from Flaveria bidentis (L.) Kuntze. The bioassay presented here shows the strong herbicidal activity of α-terthienyl on Digitaria sanguinalis, Arabidopsis thaliana and Chlamydomonas reinhardtii. The α-terthienyl-induced response of A. thaliana at the protein level was analyzed at different times. Changes in the protein expression profiles were analyzed by two-dimensional gel electrophoresis and liquid chromatography tandem mass spectrometry (LC-MS/MS) mass spectrometry. Sixteen protein spots were identified that showed reproducible changes in the expression of at least 2-fold when compared to the control. Among these 16 spots, three were up-regulated and 13 were down-regulated. The decreased expression of several proteins associated with energy production and carbon metabolism suggested that these processes were affected by α-terthienyl. To search for the candidate proteins in this screen, A. thaliana T-DNA mutants of the candidate proteins were used to test their susceptibility to α-terthienyl. Amongst the others, attkl1, a mutant of transketolase, exhibited a significantly lower sensitivity to α-terthienyl when hit compared with Col-0. Based on the identification of the proteins associated with the response to α-terthienyl by proteomics, a candidate target protein transketolase was identified.Keywords: α-terthienyl; proteomics; herbicidal mechanism; transketolase Key contribution: The mode of action of plant toxin α-terthienyl is identified for the first time, and the target is validated as transketolase by two-dimensional gel electrophoresis. Transketolase is a good candidate target for hercide design.

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Section: Discussionmentioning

confidence: 99%

Transketolase Is Identified as a Target of Herbicidal Substance α-Terthienyl by Proteomics

Zhao

Huo

Liu

et al. 2018

Toxins

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“…However, it is possible that uptake and translocation are unnecessary and that a T exerts its toxicity in the root or at the root surface. Based on Cilento's work (27)(28)(29) showing that excited triplet states may be generated enzymatically and lead to photochemical-like reactions in the absence of light, Gommers and Bakker (30) and Swain and Downum (23) proposed that peroxidases located in plant roots may catalyze reactions resulting in the dark excitation of a T and other photosensitizers. Although there is disagreement as to whether these re- actions involve energy transfer or co-oxidation of substrates (3 I), this might provide a mechanism whereby photosensitizers could exert their toxicity in darkness and would explain the killing of parasitic plant nematodes beneath the soil surface by Tagetes roots, which synthesize substantial amounts of a T (30).…”

Section: Inhibition Of Avenamentioning

confidence: 99%

Decarboxylation of lndole‐3‐Acetic Acid and Inhibition of Growth in Avena sativa Seedlings by Plant‐Derived Photosensitizers*

Brennan

1996

Photochem & Photobiology

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Abstract— A number of plant phototoxins, when supplemented with UVA (320–400 nm) radiation, are capable of sensitizing the decomposition of indole‐3‐acetic acid (IAA), as measured by release of 14CO2 from carboxyl‐labeled IAA. Alpha‐terthienyl (αT) and harmine caused significant rates of IAA decarboxylation at concentrations as low as 1 nM and were approximately 80% as effective as riboflavin and flavin mononucleotide. Partial inhibition by sodium azide indicates that the aT‐induced decarboxylation of IAA is predominately, but not entirely, a type II reaction mediated by singlet oxygen. Based on changes in UV ab sorption spectra, it appears that the hormones gibberellic acid, abscisic acid and 6‐benzylaminopurine (a cytokinin) are less susceptible to photosensitized decomposition than is IAA. Alpha‐terthienyl plus UVA also inhibited elongation growth and reduced endogenous IAA levels in Avena sativa L. coleoptile sections and promoted senescence in intact Avena seedlings. These results confirm the allelopathic potential of plant photosensitizers such as αT and indicate that the phytohormone IAA may represent an additional target for the action of photosensitizers.

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“…Cilento and co-workers have published a series of papers in which they proposed that the excited-state species generated as products of certain enzymatic reactions are capable of transferring excitation energy to other molecules, such as xanthene dyes and chlorophyll, thereby leading to their excitation and resulting in ''photochemistry and photobiology without light'' (8)(9)(10)(11). This work has served as the basis for a hypothesis proposed by several investigators to account for the light-independent toxicity of ␣T (7,12).…”

Section: Introductionmentioning

confidence: 99%

Participation of the Photosensitizer Alpha-terthienyl in thePeroxidase-catalyzed Oxidation of Indole-3-acetic acid†

Brennan

Lee

Battaglia

2000

Photochem Photobiol

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The plant photosensitizer alpha-terthienyl (alpha T) is toxic toward a variety of organisms, and normally requires exposure to ultraviolet-A radiation for activation and singlet molecular oxygen formation. However, some toxicity has also been reported to occur in the dark. One hypothesis that has been proposed to account for this light-independent toxicity is that the sensitizer becomes activated by energy transfer from the excited-state products of enzymatic reactions. We have investigated this hypothesis using the horseradish peroxidase (HRP)-catalyzed oxidation of indole-3-acetic acid (IAA), which generates indole-3-aldehyde in an excited triplet state. Light is emitted during the IAA/HRP reaction at acidic pH, is increased by inclusion of alpha T and is not observed with heat-denatured HRP. The rates of both the oxidation of IAA and the subsidence of light emission are more rapid in the IAA/alpha T/HRP system than with IAA and HRP alone, indicating that the presence of alpha T accelerates the reaction. Bleaching occurs at the wavelength of maximal alpha T absorbance and is promoted by the inclusion of IAA. Readdition of both IAA and alpha T to a spent reaction mixture is required to restore light emission after it has subsided, further suggesting that both are consumed in the reaction. We were unable to detect measurable quantities of singlet molecular oxygen formation in this system. These results do not support the energy transfer hypothesis, but instead are more compatible with a model proposed by Krylov and Chebotareva [Krylov, S. N. and A. B. Chebotareva (1993) FEBS Lett. 324, 6-8] for the co-oxidation of IAA and xanthene dyes.

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Photobiochemistry without Light: Intracellular Generation and Transfer of Electronic Energy

Cited by 4 publications

References 33 publications

Transketolase Is Identified as a Target of Herbicidal Substance α-Terthienyl by Proteomics

Transketolase Is Identified as a Target of Herbicidal Substance α-Terthienyl by Proteomics

Decarboxylation of lndole‐3‐Acetic Acid and Inhibition of Growth in Avena sativa Seedlings by Plant‐Derived Photosensitizers*

Participation of the Photosensitizer Alpha-terthienyl in thePeroxidase-catalyzed Oxidation of Indole-3-acetic acid†

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