ORIGINAL ARTICLE Development of Expressed Sequence Tags from the Pearl Oyster, Pinctada martensii Dunker Aimin Wang & Yan Wang & Zhifeng Gu & Sifa Li & Yaohua Shi & Ximing Guo Received: 12 October 2009 / Accepted: 27 March 2010 # Springer Science+Business Media, LLC 2010 Abstract The pearl oyster, Pinctada martensii, is the primary species used for the aquaculture production of marine pearls in China and Japan. Genetic tools and resources are needed to study the genome of this species and to understand the molecular basis of development, growth, host defense, pearl formation, and other important traits. In this study, we developed a set of expressed sequence tags (ESTs) for P. martensii. We constructed cDNA libraries from adult tissues and sequenced 7,128 ESTs. Clustering analysis identified 788 contigs (covering 5,769 ESTs) and 1,351 singletons, yielding a total of 2,139 unique genes. Of these unique genes, only 935 had significant (E-value ≤ 0.005) hits in GenBank, and the remaining 1,204 (56.3%) were novel. Most of the known genes are related to cellular structure, protein binding, and metabolic processes. Putative host-defense genes (86) were identified including C-type lectin, ferritin, polyubiquitin, proteases, protease inhibitors, scavenger receptors, heat shock proteins, and RAS oncogenes. The EST sequences developed in this study provide a valuable resource for future efforts on gene identification, marker development, and studies on molecular mechanism of host defense in pearl oysters. Keywords Expressed sequence tags (ESTs) . Genetic markers . Host defense genes . Pearl oyster . Pinctada martensii . Aquaculture Introduction The pearl oyster, Pinctada martensii Dunker, is a marine bivalve belonging to family Pteriidae (Pterioida, Bivalvia). It is naturally found in and around South China Sea. P. martensii is the primary species cultured for marine pearls in China and Japan, yielding about 60 tons of marine pearls annually (Guo et al. 1999; Zhang 2002). Marine pearl farming was first developed in Japan in the early 1900s. In China, large-scale farming of pearl oysters started in 1960s soon after breakthroughs in hatchery production technology that made artificial production of seeds possible. Since then, marine pearl production in China has been growing rapidly, and now, China has become the leading country in pearl production from P. martensii and produces over 30,000 kg of marine pearls each year (Zhang 2002). Pearl oyster farming has become one of the most important mariculture industries in several southern provinces of China, including Guangdong, Guangxi, and Hainan. The pearl oyster farming industry in China faces several problems. One is the deterioration of cultured stocks possibly because of the repeated reproduction of the same stock without adequate selection or monitoring of genetic diversity. Another problem is the infestation by Polydora A. Wang : S. Li Key Laboratory of Aquatic Genetic Resources and Aquaculture Ecosystem, Ministry of Agriculture, College of Fisheries and Life Science, Shanghai Ocean University, 201306 Shanghai, China A. Wang : Y. Wang : Z. Gu : Y. Shi (*) Key Laboratory of Tropic Biological Resources, Ministry of Education, Hainan Key Laboratory of Tropical Hydrobiological Technology, The Ocean College, Hainan University, Haikou 570228, China e-mail: stone70@126.com X. Guo (*) Haskin Shellfish Research Laboratory, Institute of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, NJ 08349, USA e-mail: xguo@hsrl.rutgers.edu Mar Biotechnol DOI 10.1007/s10126-010-9296-9