Adaptation to UV-B Radiation in the Ontogenesis of Arabidopsis thaliana Plants: The Participation of Ethylene, ABA, and Polyamines

The participation of ethylene signaling pathway (SPE) and polyamine spermine in the regulation of ABA accumulation during adaptation of Arabidopsis thaliana plants of the wild type (WT) and nonsynthesizing mutant spms 1-1 to moderate 7 kJ/m(2), high 14 kJ/m(2), and lethal 21 kJ/m(2) doses of UV-B radiation was investigated. It has been established that the spermine content is not a critical parameter at UV-B-induced increase in ethylene release and accumulation of ABA and putrescine. However, nonirradiated spms 1-1 plants were found to have one and a half times higher ethylene release and ABA content than intact WT plants. Blocking ethylene receptors with 1-methylcyclopropene (1-MCP) showed that, under UV-B stress, ESP does not induce ABA synthesis in WT and spms 1-1 plants but only increases its dose dependence (1.5-3-fold accumulation per day) caused by UV-B irradiation by 10-20%. At the same time, a twofold decrease in resistance to moderate to high doses of UV-B in plants WT and spms 1-1 with 1-MCP blocked ESP indicates the existence of a regulated ethylene process involved in the adaptation of plants to UV-B radiation.