Inter-individual and sun orientation driven variability reveals antagonistic salicylate and jasmonate accumulation in white-leaved rockrose

摘要

Salicylates and jasmonates may act synergically or antagonically depending on the plant growth conditions, biotic and abiotic stress factors to which plants are exposed to, and the tissue and plant species. Although possible tradeoffs between salicylate and jasmonate accumulation have been documented in model plants, information is still scarce in Mediterranean plant species, particulary in studies considering plants growing in their natural habitat. We evaluated to what extent inter-individual variability, sun orientation and diurnal variations in environmental conditions modulate not only the accumulation of salicylic acid and jasmonates (both free and conjugated forms), but also the contents of abscisic acid, hydrolyzable tannins and free phenolics, in white-leaved rockrose (Cistus albidus L.), a semi-deciduous shrub typically found in the Mediterranean basin. We found that jasmonates, most particularly the biologically active jasmonoyl-isoleucine and the jasmonic acid precursor, 12-oxo-phytodienoic acid showed a much more marked inter-individual variability than salicylic acid, abscicic acid, hydrolyzable tannins and free phenolics. East orientation reduced both abscisic acid and salicylic acid contents, while increased the accumulation of both jasmonates and hydrolyzable tannins, without affecting total free phenolic contents. Furthermore, salicylic acid and jasmonates contents, in particular those of 12-oxo-phytodienoic acid, changed throughout the day, while those of abscisic acid, hydrolyzable tannins and free phenolics remained constant. We conclude that sun orientation and inter-individual variability strongly influence stress-related phytohormones and chemical defense accumulation, with East-oriented individuals presenting higher amounts of jasmonates and hydrolyzable tannins, but less abscisic acid and salicylic acid than West-oriented ones. Results suggest a tradeoff between salicylic acid and jasmonates accumulation under stress conditions in C. albidus growing in their natural habitat.