Rapid phosphorylation of MAP kinase-like proteins in two species of Arctic kelps in response to temperature and UV radiation stress

Abstract

Mitogen-activated protein kinases (MAPKs) are a group of cytoplasmic phosphoproteins that constitute the central core of the signalling network to respond to stress in most organisms. Their role in stress responses has been extensively studied in organisms from yeast to humans, and recently, their presence has also been described in higher plants as well as in micro- and macroalgae. In this study, we demonstrate via short experiments (1h in duration), the rapid activation of two MAPKs similar to p38 and JNK of mammalian cells, in the Arctic kelps Laminaria solidungula and Saccharina latissima exposed to temperature and UV stress. The molecular mass of p38 is 40kDa in L. solidungula and 42kDa in S. latissima, while two JNKs were detected in both species, of 36 and 42kDa in L. solidungula, and 36 and 40kDa in S. latissima. These MAPKs are highly phosphorylated in response to temperature and UV light. In S. latissima, both p38 and the JNK showed higher phosphorylation at 2°C than at 7°C, while the reverse response was shown for L. solidungula. In addition, a significant increase in phosphorylation of both kinases was found following exposure to UV radiation (UVR). Exposure to PAR+UVA+UVB induced higher phosphorylation than PAR+UVA in L. solidungula, especially at 7°C. In S. latissima, this response occurred only with JNK, and no differences in p38 phosphorylation between PAR+UVA and PAR+UVA+UVB at any temperature were observed. These results indicate the possible participation of MAPK-like proteins in response to stress in Arctic kelps, and that their activation is species-specific.