Physiological and Proteomic Characterization of the Elevated Temperature Effect on Sunflower (Helianthus annuus L.) Primary Leaves

Abstract

This work examines the effect of increasing environmental temperatures, resulting from the ongoing global climate change, on the primary leaves of sunflower (Helianthus annuus L.). To do so, we examined physiological markers that are commonly used to monitor leaf development: specific leaf mass (SLM), leaf area, protein and photosynthetic pigment contents, net photosynthesis rate (PN), stomatal conductance (gs) transpiration and hydrogen peroxide (H2O2) content in the primary leaves of 42-day-old plants grown under standard diurnal and nocturnal temperatures (23 and 19°C, day/night), and under higher temperatures (33 and 29°C, day/night). Then, a proteomic approach was used to evaluate molecular alterations, at the protein level, between the two grown conditions. A total of 598387 raw spectra were obtained, yielding a total of 2343 identified protein sequences. Protein profiles were consistent with differences in protein expression between plants grown under the two temperature conditions. Interestingly, 619 (26.4%) of the identified proteins, mainly categorized in four functional groups (1-antioxidant, 2-stress and defense, 3-energy and metabolism-related, and 4-hormonal regulation proteins), exhibited increased expression in response to higher growth temperatures. These molecular differences detected in primary leaves at elevated temperatures could indicate a greater tolerance of sunflower plants to these stress conditions. This work provides a solid basis for elucidating their role and explaining the sunflower adaptive mechanisms to the increasing environmental temperature.