De Novo Characterization of Gametophyte Transcriptome in Marine Red Algae, Pyropia seriata

Pyropia seriata is one of the economically important marine red alga species cultured in East Asia including Korea. The Pyropia grows on intertidal rocks, which undergo dynamic environmental changes including temperature and desiccation in natural filed. Therefore, Pyropia have developed a variety of mechanisms to survive under those environmental stresses. To gain a better understanding of Pyropia genome, we generated 1,408,025 EST reads from the gametophytic thallus of P. seriata using 454 FLX sequencing technology and Sanger method. These ESTs were assembled into 11,218 contigs consisting of 979,313 reads, whereas 135,292 sequences remained as unassembled ESTs. The only 39.7% of contigs shared significant similarity with the e-value of ≤1E-10 with NCBI NR sequence. Comparative analysis of the transcriptome generated from gametophtes under control, heat and drought condition enable us to identify the transcripts response to heat and drought stress. The 60 different SSR motifs were discovered in 458 contigs. Trinucleotide repeat was absolutely predominant (93.9%) and GGC was the most common motif. These transcritpome sequences will provide valuable information to understand the genome structure and develop the functional genomics system for red algae including Pyropia species.