Variation in Hsp70 and Hsp101 levels in response to experimental warming in Iris pumila L.: an open-topped chamber experiment

Abstract

Global warming poses a serious threat to the survival of plant populations. To better understand plant responses to future temperature rise, two sun-exposed natural populations of Iris pumila were subjected to an open-top chamber (OTC) experiment over a two-year period. One half of all randomly selected clonal plants were experimentally warmed using clear-sided OTC, while the other half experienced ambient temperature conditions. In general, the air temperature within the OTCs was about 1-2°C higher than that outside of the OTCs. In spring and summer of 2018 and 2019, ramets of each clone growing inside and outside of OTC were analyzed for the amount of Hsp70 and Hsp101. The mean response profiles of both Hsps were parallel over time, but not flat.The amount of both Hsps tended to be greater in ramets growing inside the OTCs than in those growing outside of the OTCs, reaching its maximum in the summer. A repeated-measures profile analysis revealed statistically significant treatment, season and year effect exclusively for the Hsp101, and season effect for the Hsp70. Furthermore, profile analysis of the between-population effects showed that the mean response profiles, for both Hsps, differ between populations. Our results imply that small temperature increase can evoke changes in both the level and shape of the mean response profiles of Hsp70 and Hsp101 in I. pumila compared to that expressed at ambient air temperatures. This finding is especially important to forecast the fate of Iris populations under upcoming climate warming.