Flavonoids Can Protect Maize DNA from the Induction of Ultraviolet Radiation Damage

Abstract

Diverse flavonoid compounds are widely distributed in angiosperm families. Flavonoids absorb radiation in the ultraviolet (UV) region of the spectrum, and it has been proposed that these compounds function as UV filters. We demonstrate that the DNA in Zea mays plants that contain flavonoids (primarily anthocyanins) is protected from the induction of damage caused by UV radiation relative to the DNA in plants that are genetically deficient in these compounds. DNA damage was measured with a sensitive and simple assay using individual monoclonal antibodies, one specific for cyclobutane pyrimidine dimer damage and the other specific for pyrimidine(6,4)pyrimidone damage.Maintaining the integrity of DNA despite damage induced by UV radiation is of critica1 importance to a11 organisms that live in sunlight. Two basic strategies are available to ameliorate DNA damage: DNA repair and shielding to minimize DNA damage. Solar radiation contains wavelengths essential for photosynthesis as well as wavelengths that can damage plant DNA. Therefore, plants may have evolved particularly active DNA protection and repair mechanisms; however, to date relatively little has been established about these processes or the extent of irradiation-induced DNA damage in plants (Stapleton, 1992).UV radiation is generally classified into three wavelength ranges: UV-A (320-390 nm), UV-B (280-320 nm), and UV-C (less than 280 nm). The absorption spectrum of DNA includes wavelengths from 240 to 310 nm; however, the leve1 of solar UV that reaches the surface of the earth is high in the UV-A region of the spectrum, decreases sharply in the UV-B range, and drops to nearly zero by 290 nm (Robberecht, 1989). Many studies of the effects of UV radiation have employed germicidal lamps with peak output at 254 nm, in the UV-C region, although this wavelength is not present in sunlight at the earth's surface.Measurements in situ demonstrate that the epidermis of plants absorbs 90 to 99% of incoming UV radiation; flavonoid compounds and cuticular waxes are most likely to be the principal agents of UV absorption (Robberecht and Caldwell, 1978;Caldwell et al., 1983). Long-term damaging effects of UV radiation on plants include growth inhibition and morphological alterations; these types of damage can be observed '

Retracted: Nitric oxide enhances plant ultraviolet‐B protection up‐regulating gene expression of the phenylpropanoid biosynthetic pathway

“…Plant phenylpropanoids (as flavonoids and synapate esters) accumulate in the vacuoles of epidermal cells where they attenuate the UV component of sunlight with minimal absorption of photosynthetically active radiation (Stapleton & Walbot 1994). Flavonoids (including anthocyanins) exert antioxidant activity mainly through three ways: (1) due to their lower redox potentials (0.23-0.75 V), they are able to reduce highly oxidizing free radicals with redox potentials in the range 2.13-1.0 V as O2 -, H2O2, and OH • ; (2) flavonoids may also efficiently chelate trace metals, limiting OH • formation; and (3) flavonoids inhibit several enzymes involved in ROS generation (see Pietta 2000 and references therein).…”

Temporal synthesis and radiolabelling of the sorghum 3‐deoxyanthocyanidin phytoalexins and the anthocyanin, cyanidin 3‐dimalonyl glucoside

“…Anthocyanins constitute a large class of flavonoid compounds and are one of the most important and widespread groups of plant pigments. They serve to attract animals for pollination and seed dispersal and are also believed to be important as protectants against UV irradiation (Stapleton & Walbot, 1994 ;Holton & Cornish, 1995). In response to attempted fungal infection by both pathogenic and nonpathogenic fungi, sorghum produces a complex mixture of flavonoid secondary metabolites.…”

Effects of Epidermal Cell Shape and Pigmentation on Optical Properties of Antirrhinum Petals at Visible and Ultraviolet Wavelengths

“…Optimally, a leaf's structure would allow the penetration of photosynthetically active light to the interior while limiting the penetration of harmful UV rays. In fact, considerable evidence exists that penetration of UV-B radiation is strongly reduced by UV-absorbing compounds, chiefly flavonoids, in epidermal tissues (Robberecht andCaldwell, 1978, 1983;Tevini et al, 1991;Braun and Tevini, 1993;Day et al, 1993;Stapleton and Walbot, 1994). However, in herbaceous annuals UV-screening pigments are restricted mainly to the vacuoles of the epidermal cells, and UV-B can leak into the interior of the leaf along the anticlinal walls (Day et al, 1993).…”