Flower color morphs of Iris pumila differ in the amount of heat shock protein 70 and pigments with antioxidant properties

Abstract

Introduction: Natural populations of the dwarf bearded iris, Iris pumila, are markedly polymorphic for flower color. Selection pressures exerted by a range of abiotic and biotic factors could be involved in maintaining the polymorphism. Here we quantified the amount of the Hsp70 and the two groups of pigments with antioxidative properties: anthocyanins and carotenoids.These molecules impact abiotic stress tolerance, ultimately influencing the fitness of individual plants. Methods: A total of fifty genotypes raised in a common-garden and belonging to a corresponding color class (yellow, blue, violet, dark blue and dark violet) were surveyed. One fully developed leaf and a flower from each genotype were analyzed for the Hsp70 amount and pigments concentration. Results: The Western blot analysis revealed the presence of one isoform for the Hsp70 in leaf and two isoforms in flower organs. In both vegetative and reproductive tissues the amount of Hsp70 was found to be the lowest in yellow colored genotypes compared to other color classes. In violet and blue flowers, the concentration of Hsp70 decreased gradually from light to dark colored variants. Conversely, the concentration of anthocyanins was found to be higher in darker than in the lighter color morphs. An inverse trend was observed for the total carotenoids concentration. Conclusion: This study revealed that each I. pumila color genotype produces a unique amount of Hsp70 and antioxidative pigments in both the vegetative and reproductive plant parts, in order to protect cellular homeostasis under fluctuating temperature conditions prevailing in its population.