A novel stress-acclimation response in Spirodela punctata (Lemnaceae): 2,4,6-trichlorophenol triggers an increase in the level of an extracellular peroxidase, capable of the oxidative dechlorination of this xenobiotic pollutant

Peroxidases are haem‐containing enzymes capable of oxidizing a wide range of substrates. This article describes the presence of peroxidase activity in the growth medium of axenic Spirodela punctata (Lemnaceae) cultures. It was found that the release of extracellular peroxidase activity is specifically enhanced by phytotoxic, halogenated phenols but not by other abiotic stress‐factors, elicitors or plant metabolites. Based on the concentration dependence of 2,4,6‐trichlorophenol (TCP)‐enhanced peroxidase release, it is concluded that release is not simply a consequence of physiological damage, but rather requires metabolically healthy fronds. In vitro studies (UV/VIS spectroscopy and liquid chromatography/mass spectrometry) show that the extracellular duckweed peroxidase (SpEx), which was partially purified from Spirodela growth medium, is capable of catalysing the oxidative dechlorination of TCP with hydrogen peroxide as the electron acceptor. It is proposed that the ability of S. punctata to specifically sense environmentally persistent phytotoxic chlorophenols, and to respond by increasing extracellular levels of a peroxidase capable of catalysing their oxidative dechlorination, is part of the protection strategy of this aquatic plant against xenobiotic stress.     

Behaviour and stress response during capture and handling of the red-billed chough Pyrrhocorax pyrrhocorax (Aves: Corvidae)

We studied the effect of capture and handling on free-living red-billed choughs Pyrrhocorax pyrrhocorax . We analysed the association between bird behavioural response and individual health, breeding status, sex, and age. Active responses (aggression towards the ringer, screaming) were more common in the breeding period, and in individuals with a high heterophils to lymphocytes ratio, indicating poor physiological condition and/or high chronic stress. Adults were more aggressive than juveniles and yearlings, and females were more aggressive than males. Sex, age, and condition differences were also recorded in the spectrotemporal output of distress calls. Birds with a screaming/active response appeared to be more stress-susceptible than passive and silent individuals, and this response was stronger during the energy demanding period of reproduction. The results obtained suggest that the response of the red-billed chough during capture might primarily reflect stress-susceptibility, although a number of potential alternative explanations are discussed.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 846–855.     

The proteomic response of sea squirts (genus Ciona) to acute heat stress: a global perspective on the thermal stability of proteins

Congeners belonging to the genus Ciona have disparate distributions limited by temperature. Ciona intestinalis is more widespread with a cosmopolitan distribution ranging from tropical to sub-arctic zones, while Ciona savignyi is limited to temperate-latitudes of the northern Pacific Ocean. To compare the heat stress response between congeners, we quantified changes in protein expression using proteomics. Animals were exposed to 22 °C, 25 °C, and 28 °C for 6 h, then recovered at a control temperature (13 °C) for 16 h (high heat stress experiment). In a second experiment we exposed animals to lower levels of heat stress at 18 °C, 20 °C, and 23 °C, with a 16 °C control. A quantitative analysis, using 2D gel electrophoresis and MALDI-TOF/TOF mass spectrometry (with a 69% and 93% identification rate for Ciona intestinalis and Ciona savignyi, respectively), showed changes in a number of protein functional groups, including molecular chaperones, extracellular matrix proteins, calcium-binding proteins, cytoskeletal proteins and proteins involved in energy metabolism. Our results indicate that C. intestinalis maintains higher constitutive levels of molecular chaperones than C. savignyi, suggesting that it is prepared to respond faster to thermal stress. Systematic discrepancies between estimated versus predicted molecular masses of identified proteins differed between protein families and were more pronounced under high heat conditions, suggesting that thermal sensitivities are lower for cytoskeletal proteins and ATP-synthase than for any other protein group represented on 2D gels.