Differential Expression Profile Of Litopenaeus Vannamei Injected With LvJNK-dsRNA And Functional Analysis Of Lvp38 Isoforms

Litopenaeus vannamei is one of the most important commercial marine species worldwide.However,viral diseases threaten the healthy development of shrimp aquaculture.In order to develop efficient control strategies against viral diseases,researchers have begun focusing increasing attention to the molecular mechanism of shrimp innate immunity.JNK signaling pathway is an important signaling pathway in mammalian cells,and it can participate in in regulating many cellular processes including inflammation,cell stress response,cell differentiation,cell division,cell proliferation,metabolism,motility and apoptosis.Previous studies in L.vannamei showed that LvJNK could be activated by WSSV.In order to further understand the function of LvJNK during WSSV infection,we sequenced the transcriptome of L.vannamei in which the transcription of JNK was inhibited by RNAi.By comparing this data with that from the control group,230 differential genes were screened,in which 112 genes were up-regulated and 118 genes were down-regulated.We found that some differential expression genes have been reported in previous studies as the upstream or downstream protein of JNK.These data could give us clues to study the functions of JNK pathway in shrimp.p38 is another mitogen-activated protein kinase of MAPK superfamily,which can be activated by multiple exogenous stimuli to regulate the expression of downstream transcription factors.Our previous study indicated Litopenaeus vannamei p38 was phosphorylated after WSSV infection.Meanwhile we found that there are three different isoforms in Litopenaeus vannamei: lvp38 a,lvp38b,and lvp38 c.In this study,we further studied the functional difference in these three isoforms.First,we obtained the genomic sequence of lvp38.This sequence is composed of 12 exons and 11 introns,and the sequence difference of lvp38 isoforms is because of exon difference.The tissue distribution analysis shows that they were expressed in all detected tissues,and the expression level of lvp38 c was lowest.Using insect cell expression system,we found that all three lvp38 isoforms were mainly located in the cytoplasm.To further understand the functional difference of lvp38 isoforms,we analyzed the transcriptional levels of lvp38 by Real-time PCR,when shrimps were challenged by different pathogens.The results showed that the transcriptional level of lvp38 was significantly downregulated after WSSV infection,but the lvp38 transcriptional levels have an increase after Vibrio parahaemolyticus infection.The varied levels of transcription among three isoforms have no obvious difference during WSSV and V.parahaemolyticus infection.In addition,we studied the role of lvp38 during WSSV infection.We found that the apoptosis of the hemocytes was induced during WSSV infection.When the transcript level of lvp38 was inhibited by RNA interference,the levels of caspase 3/7 activity and ie1 viral gene transcript were both up-regulated.It suggested that lvp38 might play an antiviral role through the inhibition of apoptosis.Furthermore,we expressed three lvp38 isoforms in insect cells.The result confirmed that overexpressed lvp38 inhibited apoptosis.In this study,we explored the role of LvJNK by transcriptome sequencing and RNA interference and analyze the functional difference among three isoform of lvp38.These results will help us better understand the relationship between shrimp and pathogen.