Identification of cold responsive genes in Pacific white shrimp (Litopenaeus vannamei) by suppression subtractive hybridization.

ABSTRACT

The Pacific white shrimp (Litopenaeus vannamei) is one of the most widely cultured shrimp species in the world. Despite L. vannamei having tropical origins, it is being reared subtropically, with low temperature stress being one of the most severe threats to its growth, survival and distribution. To unravel the molecular basis of cold tolerance in L. vannamei, the suppression subtractive hybridization (SSH) platform was employed to identify cold responsive genes in the hepatopancreas of L. vannamei. Both forward and reverse cDNA libraries were constructed, followed by dot blot hybridization, cloning, sequence analysis and quantitative real-time PCR. These approaches identified 92 cold induced and 48 cold inhibited ESTs to give a total of 37 cold induced and 17 cold inhibited contigs. Some of the identified genes related to stress response or cell defense, such as tetraspanins (TSPANs), DEAD-box helicase, heat shock proteins (HSPs) and metallothionein (MT), which were more abundant in the forward SSH library than in the reverse SSH library. The most abundant Est was a tetraspanin-8 (TSPAN8) homolog dubbed LvTSPAN8. A multiple sequence alignment and transmembrane domain prediction was also performed for LvTSPAN8. LvTSPAN8 expression was also examined in the gills, muscle, heart and hepatopancreas following cold exposure and showed the highest expression levels in the hepatopancreas. Overall, this study was able to identify several known genes and novel genes via SSH that appear to be associated with cold stress and will help to provide further insights into the molecular mechanisms regulating cold tolerance in L. vannamei.