Light filtering by epidermal flavonoids during the resistant response of cotton to Xanthomonas protects leaf tissue from light-dependent phytoalexin toxicity

Ultraviolet-absorbing pigments accumulate in red epidermal cells surrounding and sometimes over infection sites. The two principal ones have been identified as cyanidin-3- O-β-glucoside ( 1) and quercetin-3- O-β-glucoside ( 2). 2,7-Dihydroxycadalene and lacinilene C, sesquiterpenoid phytoalexins tha...

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Bibliographic Details
Published in:	Phytochemistry (Oxford) Vol. 69; no. 12; pp. 2320 - 2328
Main Authors:	Edwards, W. Ray, Hall, Judy A., Rowlan, Alan R., Schneider-Barfield, Tama, Sun, Tzeli Julia, Patil, Mohini A., Pierce, Margaret L., Fulcher, R. Gary, Bell, Alois A., Essenberg, Margaret
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier Ltd 01-09-2008 Elsevier
Subjects:	2,7-Dihydroxycadalene Anthocyanin Biological and medical sciences Chemical constitution Chrysanthemin cotton Cyanidin-3- O-β-glucoside Ecological biochemistry epidermis (plant) flavonoids Flavonoids - physiology Flavonol glycoside Fundamental and applied biological sciences. Psychology Gossypium - drug effects Gossypium - physiology Gossypium - radiation effects Gossypium hirsutum Gossypium hirsutum L hypersensitive response Isoquercitrin Lacinilene C Light Malvaceae Phytoalexin phytoalexins phytotoxicity Pigmentation - drug effects Plant Diseases Plant Leaves - drug effects Plant Leaves - physiology Plant Leaves - radiation effects plant pathogenic bacteria Plant physiology and development Quercetin-3- O-β-glucoside resistance mechanisms Sesquiterpene Sesquiterpenes sesquiterpenoids solar radiation Spectrophotometry Sunlight Terpenes - chemistry Terpenes - toxicity ultraviolet radiation Upland cotton UV damage UV protection Xanthomonas campestris pv. malvacearum Malvaceae Anthocyanin UV protection Xanthomonas campestris pv. malvacearum Sesquiterpene Chrysanthemin Upland cotton Isoquercitrin Cyanidin-3- O-β-glucoside Ecological biochemistry Lacinilene C 2,7-Dihydroxycadalene Phytoalexin Flavonol glycoside Gossypium hirsutum L Quercetin-3- O-β-glucoside UV damage Pseudomonadales Plant pathogen Toxicity Fiber crop Flavonoid Prevention Polyphenol Dicotyledones Light Sesquiterpenes Angiospermae Bacteria Pseudomonadaceae Glycoside Protection Glucoside Epidermis Plant leaf Xanthomonas campestris Ultraviolet irradiation Quercetin-3-O-β-glucoside Quercetin Phenols Spermatophyta Gossypium hirsutum Lesion Cyanidin-3-O-β-glucoside
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Summary:	Ultraviolet-absorbing pigments accumulate in red epidermal cells surrounding and sometimes over infection sites. The two principal ones have been identified as cyanidin-3- O-β-glucoside ( 1) and quercetin-3- O-β-glucoside ( 2). 2,7-Dihydroxycadalene and lacinilene C, sesquiterpenoid phytoalexins that accumulate at infection sites during the hypersensitive resistant response of cotton foliage to Xanthomonas campestris pv. malvacearum, have light-dependent toxicity toward host cells, as well as toward the bacterial pathogen. Adaxial epidermal cells surrounding and sometimes covering infection sites turn red. The red cells exhibited 3–4-fold higher absorption at the photoactivating wavelengths of sunlight than nearby colorless epidermal cells. Red epidermal cells protected underlying palisade mesophyll cells from the toxic effects of 2,7-dihydroxycadalene plus sunlight, indicating a role for epidermal pigments in protecting living cells that surround infection sites from toxic effects of the plant’s own phytoalexins. A semi-quantitative survey of UV-absorbing substances extracted from epidermal strips from inoculated and mock-inoculated cotyledons indicated that the principal increase in capacity to absorb the photoactivating wavelengths was due to a red anthocyanin and a yellow flavonol, which were identified as cyanidin-3- O-β-glucoside and quercetin-3- O-β-glucoside, respectively.
Bibliography:	http://hdl.handle.net/10113/20684 http://dx.doi.org/10.1016/j.phytochem.2008.05.021
ISSN:	0031-9422 1873-3700
DOI:	10.1016/j.phytochem.2008.05.021