Phosphorylation of MAPK-like proteins in three intertidal macroalgae under stress conditions

Abstract

The presence and activation of mitogen-activated protein kinase (MAPK)-like pro- teins in 3 macroalgae with different morphology and phylogeny (Ulva rigida, Ellisolandia elon- gata and Cystoseira tamariscifolia) were studied during the experimental workshop of the Inter- national Group on Aquatic Productivity. Macroalgae were exposed in the short term (days) to different carbon and nitrogen levels and raised temperature (+4°C over ambient conditions) in mesocosms under controlled conditions mimicking current and future ocean acidification. Three MAPK-like proteins of 40, 42 and 44 kDa similar to mammalian p38 kinase (p38), stress-activated protein kinase/c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) were detected, and their phosphorylation occurred both under low- and high-carbon as well as under low- and high-nitrogen conditions (LC, HC, LN, HN, respectively). Moreover, increased temperature led to differential responses of the MAPKs in these species. In U. rigida, p38 phos- phorylation initiated the acclimation to temperature stress in LC, while this role was mainly played by JNK in HC during the first 24 h. In E. elongata, p38 was primarily activated in LCLN and in HC treatment. In C. tamariscifolia, JNK was mainly activated in LN during the first 24 h, while both p38 and JNK were activated in HC, but only after 24 h at elevated temperature. U. rigida was the only species in which ERK phosphorylation increased at increased temperature. These results suggest that both E. elongata and C. tamariscifolia are close to the upper limit of their temperature range at the temperatures tested in this work, and that Ulvales could have physiological advan- tages in Medi terranean systems in a scenario of future CO2-enrichment with high nitrogen loads.