CHARACTERISTIC OF A VIRAL PROTEIN (VP-15) OF WHITE SPOT SYNDROME VIRUS ISOLATED FROM INFECTED TIGER SHRIMP Penaeus monodon

Since 1990, tiger shrimp culture in Indonesia was faced the problems by the decrease environment quality and the viral/bacterial diseases. At least 20 viruses causing the shrimp diseases have been reported; where white spot syndrome virus (WSSV) is one of the major virulent viruses infected the shrimp in pond culture and hatchery. Structural proteins of WSSV, including VP-15, play very important roles in virus infection and morphogenesis process. VP-15 is located in nucleocapsid of virion virus, which involves in the life cycle of WSSV in host cells. The present study was conducted to isolate and characterize the VP-15 from infected tiger shrimp in providing a material base to construct the RNAi technology for controlling the shrimp diseases in aquaculture.

The tiger shrimp were collected from the pond culture at Takalar regency, South Sulawesi. The nine positively white spot diseases were selected for further study, such as 3 samples from outbreak in 2012, 1 sample in 2013, and 5 samples in 2014. DNA genome was extracted by CTAB method and diseases detection was conducted by using the commercial kit. PCR technique was performed to isolate the gene of VP-15 and target gene was then sequenced. Nucleotide sequence analysis was done by Genetyx 7.0 and BLAST-N/P program from NCBI.

A gene encoding VP-15 was successfully isolated in fragment size at 243 bp and had very high similarity (up to 99%) compared with VP-15 in GenBank. The VP-15 consisted of 80 amino acids, two start codons, one stop codon, and one Kozak context, and the VP-15 was rich amino acid of lysine (21.3%), arginine (22.9%) and serine (24.6%) (Figure 1). Three clusters were revealed in the present study corresponding to the time (year) of isolates collection (Figure 2). The characteristic of VP-15 suggested the great potentiality to be used as a material base to develop the RNAi technology.