Background The pearl oyster Pinctada fucata martensii is an economically valuable shellfish for seawater pearl production, and production of pearls depends on its growth. To date, the molecular mechanisms of the growth of this species remain poorly understood. The transcriptome sequencing has been considered to understanding of the complexity of mechanisms of the growth of P. f. martensii. The recently released genome sequences of P. f. martensii , as well as emerging Pacific Bioscience (PacBio) single-molecular sequencing technologies, provide an opportunity to thoroughly investigate these molecular mechanisms. Results Herein, the full-length transcriptome was analysed by combining PacBio single-molecule long-read sequencing (PacBio sequencing) and Illumina sequencing. A total of 20.65 Gb of clean data were generated, including 574,561 circular consensus reads, among which 443,944 full-length non-chimeric (FLNC) sequences were identified. Through transcript clustering analysis of FLNC reads, 32,755 consensus isoforms were identified, including 32,095 high-quality consensus sequences. After removing redundant reads, 16,388 transcripts were obtained, and 641 fusion transcripts were derived by performing fusion transcript prediction of consensus sequences. Alternative splicing analysis of the 16,388 transcripts was performed after accounting for redundancy, and 9097 gene loci were detected, including 1607 new gene loci and 14,946 newly discovered transcripts. The original boundary of 11,235 genes on the chromosomes was corrected, 12,025 complete open reading frame sequences and 635 long non-coding RNAs (LncRNAs) were predicted, and functional annotation of 13,482 new transcripts was achieved. Two thousand three hundred eighteen alternative splicing events were detected. A total of 228 differentially expressed transcripts (DETs) were identified between the largest (L) and smallest (S) pearl oysters. Compared with the S, the L showed 99 and 129 significantly up-and down-regulated DETs, respectively. Six of these DETs were further confirmed by quantitative real-time RT-PCR (RT-qPCR) in independent experiment. Conclusions Our results significantly improve existing gene models and genome annotations, optimise the genome structure, and in-depth understanding of the complexity and diversity of the differential growth patterns of P. f. martensii .

Phosphatase and tensin homolog deleted on chromosome ten (PTEN) has been found to regulate longevity through the PI3K/Akt/FoxO pathway and maintenance of genome integrity in worms, flies, and mammals. However, limited information is available on the roles of PTEN in longevity of aquatic animals. Here we extended this paradigm using two closely related Argopecten scallops, Argopecten purpuratus, and Argopecten irradians, with significantly distinct life spans, which are commercially important bivalve species for fishery and aquaculture in China, United States, Peru, and Chile. The ORFs of the ApPTEN and AiPTEN were 1,476 and 1,473 bp, which encoded 491 and 490 amino acids, respectively. There were 48 synonymous and 16 non-synonymous SNPs and one InDel of three nucleotides between ApPTEN and AiPTEN, resulting in variations in 15 amino acids and lack of S453 in AiPTEN. Differences in conformation and posttranslational modification were predicted between ApPTEN and AiPTEN, which may indicate different activities of ApPTEN and AiPTEN. When the animals were subjected to nutrition restriction, the expression of both ApPTEN and AiPTEN was upregulated, with AiPTEN responded faster and more robust than ApPTEN. Ionizing radiation induced significantly elevated expression of ApPTNE but not AiPTEN in the adductor muscle, and the mortality rate of A. purpuratus was significantly lower than that of A. irradians, indicating that ApPTNE may play a protective role by maintaining the genome integrity. RNAi of ApPTNE significantly downregulated the expression of its downstream regulated genes known to favor longevity, such as FoxO, Mn-SOD, and CAT. These results indicated that PTEN may contribute to the longevity of A. purpuratus through regulation of nutrient availability and genomic stability, probably via PI3K/Akt/FoxO pathway. Our study may provide new evidence for understanding of the conservative functions of PTEN in regulation of lifespan in animals and human, and it may also benefit the selection of scallops strains with long lifespan and thus larger size.