RNA-Seq revealed complex response to heat stress on transcriptomic level in Saccharina japonica (Laminariales, Phaeophyta)

Saccharina japonica is a cold-temperate species; it often suffers heat stress during cultivation in temperate and subtropical zone in China. In this study we investigated the response of this alga to heat stress on transcriptomic level. A total of 947 genes (1.32 %) were identified as different expression genes (DEGs), out of which 548 and 399 genes were respectively up- and down-regulated by the heat stress. Among the 138 enriched gene ontology (GO) terms, “cell part”, “binding” and “cellular process” ranked as the first three GO terms that contained the most DEGs. A total of 47 pathways involved 119 DEGs were enriched. Over half of these DEGs were involved in “protein processing in endoplasmic reticulum”, “metabolic pathway” and “biosynthesis of secondary metabolites”. Manual classification of DEGs indicated that 155 DEGs were divided into nine groups, including heat shock protein, antioxidant system, protein synthesis and degradation, and so on. The results indicated that the heat stress triggered complex response of S. japonica; in turn, S. japonica adjusted its physiological and metabolic processes to adapt to and survive the heat stress. The identified DEGs will shed light on the heat tolerance mechanism of S. japonica and benefit future breeding of variety with heat tolerance.