Laminariales Host Does Impact Lipid Temperature Trajectories of the Fungal Endophyte Paradendryphiella salina (Sutherland.)

Abstract

Kelps are colonized by a wide range of microbial symbionts. Among them, endophytic fungi remain poorly studied, but recent studies evidenced yet their high diversity and their central role in algal defense against various pathogens. Thus, studying the metabolic expressions of kelp endophytes under different conditions is important to have a better understanding of their impacts on host performance. In this context, fatty acid composition is essential to a given algae fitness and of interest to food web studies either to measure its nutritional quality or to infer about its contribution to consumers diets. In the present study, Paradendryphiella salina, a fungal endophyte was isolated from Saccharina latissima (L.) and Laminaria digitata (Hudson.) and its fatty acid composition was assessed at increasing salinity and temperature conditions. Results showed that fungal composition in terms of fatty acids displayed algal-dependent trajectories in response to temperature increase. This highlights that C18 unsaturated fatty acids are key components in the host-dependant acclimation of P. salina to salinity and temperature changes.

Keywords: Paradendryphiella salina; fatty acids; fungal endophytes; laminariales.

Figure 1

Concentrations ($\mathsf{\mu }\mathrm{g} {\mathrm{g}}^{-1}$) of the 7 most abundant fatty acids. (a) Higher concentrations and (b) lower concentrations of endophytic P. salina isolated from L. digitata (LD) or S. latissima (SL) and grown at different salinities (23.5, 50 and 70 PSU) and temperatures (10, 18 and 25 ${}^{\circ }$C). One-way Welch ANOVA (W) or One-way ANOVA (A) has been performed depending on the result of Bartlett test: n.s. = not significant, * p < 0.05, ** p < 0.01, and *** p < 0.001.

Figure 2

Fatty acid trajectories of endophytic P. arenaria isolated from L. digitata (LD) or S. latissima (SL) grown at different salinities (23.5, 50 and 70 PSU) and different temperatures (10, 18 and 25 ${}^{\circ }$C): (a–c) PCA scores. (d) $FA{I}_{18-C}$ index calculated with relative contributions (%) of major C18 fatty acids showing opposite trends in the acclimation of P. salina to temperature between host algae. $\alpha =$ angle between the two regression lines.