Phenol-Oxidizing Peroxidases Contribute to the Protection of Plants from Ultraviolet Radiation Stress

Abstract

We have studied the mechanism of UV protection in two duckweed species (Lemnaceae) by exploiting the UV sensitivity of photosystem II as an in situ sensor for radiation stress. A UV-tolerant Spirodela punctata G.F.W. Meyer ecotype had significantly higher indole-3-acetic acid (IAA) levels than a UV-sensitive ecotype. Parallel work on Lemna gibba mutants suggested that UV tolerance is linked to IAA degradation rather than to levels of free or conjugated IAA. This linkage is consistent with a role for class III phenolic peroxidases, which have been implicated both in the degradation of IAA and the cross-linking of various UV-absorbing phenolics. Biochemical analysis revealed increased activity of a specific peroxidase isozyme in both UV-tolerant duckweed lines. The hypothesis that peroxidases play a role in UV protection was tested in a direct manner using genetically modified tobacco (Nicotiana sylvestris). It was found that increased activity of the anionic peroxidase correlated with increased tolerance to UV radiation as well as decreased levels of free auxin. We conclude that phenol-oxidizing peroxidases concurrently contribute to UV protection as well as the control of leaf and plant architecture.

Differential Activity of Peroxidase Isozymes in Response to Wounding, Gypsy Moth, and Plant Hormones in Northern Red Oak (Quercus rubra L.)

“…The extraction buffer contained 0.1-M potassium phosphate, pH 7.0, and 9% (w/v) polyvinylpolypyrrolidone. To break up cellular membranes, 10% (v/v) Triton X-100 was added to the extraction buffer at a rate of 1.6 µl/mg tissue (Jansen et al, 2001). Initially, extracts were centrifuged at 1100 × g for 15 min at 4 • C; however, the viscosity of extracts from older leaves hindered adequate separation of the supernatant and pellet.…”

An anionic class III peroxidase from zucchini may regulate hypocotyl elongation through its auxin oxidase activity

“…Nevertheless, although in some cases spatial and temporal localization or indirect evidence might indicate their involvement in speciWc mechanisms (Ostergaard et al 2000;Jansen et al 2001), the in planta function of a single isoform has never been clearly characterized. For example, the identiWcation of a tobacco peroxidase whose antisense suppression led to a signiWcantly lower lignin content and vascular tissue modiWcation was reported (Blee et al 2003).…”

Ultraviolet-B exposure induces photo-oxidative damage and subsequent repair strategies in a desert cyanobacterium Microcoleus vaginatus Gom.

“…To assess the effects of enhanced UV-B on living organisms, it is important to consider the injury of UV-B radiation to different species. Many studies have revealed that UV-B radiation induces a degradation of the physiological activity and an enhancement of the oxidative stress in higher plants and some cyanobacteria [15,22]. Microcoleus vaginatus Gom., a filamentous cyanobacterium, is a dominant species in many microbiotic crusts throughout the world [5,9,21].…”