EVIDENCE OF A LATENT OXIDATIVE BURST IN RELATION TO WOUND REPAIR IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS¹

Abstract

We investigated the kinetics and composition of the second phase of the wound repair process of Dasycladus vermicularis ([Scropoli] Krasser) using fluorescent probes, chromatography, UV spectroscopy, and histochemistry. Our new evidence supports the hypothesis that the second phase of wound repair (initiated at approximately 35-45 min postinjury) is based on the activation of an oxidative burst that produces micromolar H 2 O 2 levels. These results provide evidence of peroxidase activity at the wound site, real-time measurements of an oxidative burst, and catechol localization in wound plugs. Strong evidence is presented indicating that the biochemical machinery exists for oxidative cross-linking to ensue in the wound-healing process of D. vermicularis.

Toxin release in response to oxidative stress and programmed cell death in the cyanobacterium Microcystis aeruginosa

“…This type of assay has been commonly employed as a marker for stress response in higher plants (Orozco-Cardenas and Ryan, 1999) and marine algae (Collen and Pedersen, 1994;Küpper et al, 2002;Ross et al, 2005). The response is based on the reaction of hydrogen peroxide with the fluorogenic probe dichlorofluorescein diacetate (DCFH-DA, Invitrogen Corp., Carlsbad, CA, USA).…”

“…The total volume was increased to 2000 l in filtered seawater. H 2 O 2 was quantified fluorometrically on a Biorad VersaFluor fluorometer (Bio-Rad; excitiation: 488 nm, emission: 525 nm) using the methods of Ross et al (2005). Biologically relevant concentrations of commercially obtained H 2 O 2 (Sigma) were used as standards.…”

“…However, the biological production of H 2 O 2 may reflect an imbalanced state of redox within the chloroplast and thus may serve as a proxy for cellular stress (Twiner and Trick, 2000;Choo et al, 2004). Among the approaches used to quantify H 2 O 2 , the fluorogenic method is quite successful and has subsequently been used to monitor oxidative stress in a variety of photosynthetic organisms Ross et al, 2005).…”

Non-enzymatic isolation of somatic cells fromKappaphycusspp. andEucheuma denticulatum(Solieriaceae, Rhodophyta)

“…Evolution of bubbles, swelling of tissues and eventual stripping off of the outer wall were among the immediate effects which have been observed in some species of brown seaweeds 4 h after external treatment with high levels of H 2 O 2 (Hasebe, 1978). These changes have been attributed to the decomposition of H 2 O 2 into molecular oxygen as it permeates the tissues, or due to the reaction of H 2 O 2 and endogenous enzymes (peroxidase and catalase) in the intercellular matrices to release water before an electron donor can be oxidized (Ross et al, 2005). Induced production of H 2 O 2 significantly decreases the photosynthetic activity in K. alvarezii (Barros et al, 2003) and is manifested as bleaching and discolouration of the pigmented cortical cells of the PBH 2 O 2 -treated tissues of Kappaphycus and E. denticulatum.…”

“…H 2 O 2 is a reactive oxygen species (ROS) that has been associated with 'oxidative burst' in ice-ice disease incidences among the farmed seaweeds Kappaphycus and Eucheuma, and among macroalgae subjected to physical injury and environmental stress Barros et al, 2003;Weinberger, 2007). The manifestations of ice-ice disease include softening of tissues, and in severe conditions liquefaction and loss of structural integrity of the thallus (Mendoza et al, 2002;Neish, 2003 (Kupper et al, 2001;Ross et al, 2005). These effects are mimicked in plant cells treated externally with high levels of H 2 O 2 (Wojtaszek, 1997), and the shift in plant responses from harmful to beneficial consequences is dose dependent (Kotchoni & Gachomo, 2006).…”