role of ABA in the freezing injury avoidance in two Hypericum species differing in frost tolerance and potential to synthesize hypericins

• Published in: Plant cell, tissue and organ culture tissue and organ culture, 2015-07, Vol.122 (1), p.45-56
• Main Authors: Bruňáková, Katarína, Petijová, Linda, Zámečník, Jiří, Turečková, Veronika, Čellárová, Eva
• Format: Article
• Language: English
• Subjects: Abscisic acid; Avoidance; Bioactive compounds; Biomedical and Life Sciences; Biosynthesis; cold stress; Cold tolerance; cold zones; Dehydration; Depletion; Endemic species; Environmental factors; Freezing; Frost; frost injury; frost resistance; Hypericin; Hypericum; Hypericum canariense; Hypericum perforatum; indigenous species; Injury prevention; Life Sciences; Low temperature; Metabolites; Original Paper; Plant Genetics and Genomics; Plant Pathology; Plant Physiology; Plant Sciences; Secondary metabolites; temperature; Temperature effects
• ISSN: 0167-6857; 1573-5044
• DOI: 10.1007/s11240-015-0748-9

Cold stress is a major environmental factor that limits the distribution of plants and determines the spectrum and amount of secondary metabolites with a protective function. The most studied representative of the genus Hypericum, H. perforatum L. (St. John’s wort), is known as a producer of the photodynamic pigment hypericin, the unique bioactive compound structurally belonging to naphtodianthrones. In relation to the cosmopolitan distribution, we hypothesised that low temperature stress could increase the content of naphtodianthrones as a part of the adaptive mechanisms. Two strategies in preventing the freezing injury in the genus Hypericum were defined. Based on a frost-killing temperature (LT₅₀) in untreated (control) plants and more than a 10 °C decrease in LT₅₀ in cold-acclimated plants, we demonstrated the freezing tolerance for H. perforatum. On the contrary, the freezing avoidance was preferable in H. canariense—the species endemic to (sub)tropical Canary Islands and Madeira. The freezing tolerance/avoidance was related to the course of ABA accumulation/depletion in H. perforatum/H. canariense under a subfreezing temperature of −4 °C; however, the effect of dehydration or application of 76 μM ABA on the level of endogenous ABA was comparable. The 48-h exposure of H. perforatum control plants to −4 °C resulted in a 1.6-fold increase in the content of naphtodianthrones, along with the 1.5-fold increase of ABA. On the contrary, neither dehydration nor exogenous ABA stimulated the biosynthesis of these compounds. Our findings indicate possible integration of ABA signalling into naphtodianthrones biosynthesis under subfreezing conditions; this mechanism could be modified by plant tolerance to cold environments.