A deficiency in salicylic acid alters isoprenoid accumulation in water-stressed NahG transgenic Arabidopsis plants

Previous studies have shown that salicylic acid is ail essential component of the plant resistance to pathogens and participates in the plant response to adverse environmental conditions. The present study was aimed at better understanding the response of salicylic acid-deficient transgenic NahG Arabidopsis plants to water deficit conditions, with an especial emphasis on the effects of salicylic acid on isoprenoid accumulation. Total monoterpene contents, chlorophylls and a-tocopherol (which contain a diterpene phytyl moiety in their molecule) and the tetraterpenes, carotenoids, were measured in wild type and NahG Arabidopsis plants exposed to 2 weeks of water deficit. The results show that a salicylic acid deficiency in NahG tansgenic lines suppressed the water stress-induced loss of chlorophylls and carotenoids observed in the wild type. alpha-Tocopherol accumulation was also affected in NahG plants, which showed lower levels of this antioxidant both under irrigated and water stress conditions. In addition, accumulation of monoterpenes was suppressed in NahG plants both under irrigated and water stress conditions, although the effects were more apparent under stress and, as this was more severe. We conclude that salicylic acid affects isoprenoid accumulation in leaves specially under water stress conditions. (c) 2007 Elsevier Ireland Ltd. All rights reserved.