title: Betalain induction by l-DOPA application confers photoprotection to saline-exposed leaves of Disphyma australe.
abstract: The capacity to synthesize betalains has arisen in diverse phylogenetic lineages across the Caryophyllales, and because betalainic plants often grow in deserts, sand dunes, or salt marshes, it is likely that these pigments confer adaptive advantages. However, possible functional roles of foliar betalains remain largely unexplored and are difficult to test experimentally. We adopted a novel approach to examine putative photoprotective roles of betalains in leaves for which chloroplast function has been compromised by salinity. Responses of l-DOPA-treated red shoots of Disphyma australe to high light and salinity were compared with those of naturally red- and green-leafed morphs. Betalain content and tyrosinase activity were measured, and Chl fluorescence profiles and H2 O2 production were compared under white, red or green light. Green leaves lacked tyrosinase activity, but when supplied with exogenous l-DOPA they produced five betacyanins. Both the naturally red and l-DOPA-induced red leaves generated less H2 O2 and showed smaller declines in photosystem II quantum efficiency than did green leaves when exposed to white or green light, although not when exposed to red light. Light screening by epidermal betalains effectively reduces the propensity for photoinhibition and photo-oxidative stress in subjacent chlorenchyma. This may assist plant survival in exposed and saline environments.
authors: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6140, New Zealand.
authors: Gagandeep
authors: G
authors: Jain
authors: New Zealand Institute for Plant and Food Research Limited, Private Bag 11-600, Palmerston North, New Zealand.
authors: Kathy E
authors: KE
authors: Schwinn
authors: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6140, New Zealand.
authors: Kevin S
authors: KS
authors: Gould
mesh_terms: D050858:Betalains / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005452:Fluoresceins / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007980:Levodopa / Q000494:pharmacology*; D008027:Light; D019684:Magnoliopsida / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D014442:Monophenol Monooxygenase / Q000378:metabolism; D055668:Photochemical Processes / Q000187:drug effects / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010858:Pigmentation / Q000187:drug effects / Q000528:radiation effects; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018520:Plant Shoots / Q000187:drug effects / Q000528:radiation effects; D012965:Sodium Chloride / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D005452:Fluoresceins; D045332:Photosystem II Protein Complex; C065013:2',7'-dichlorodihydrofluorescein; D050858:Betalains; D012965:Sodium Chloride; D007980:Levodopa; D006861:Hydrogen Peroxide; D014442:Monophenol Monooxygenase
keywords: Disphyma australe; betalain; l-DOPA; leaves; photoprotection; salinity; tyrosinase