Roles of small RNAs in the immune defense mechanisms of crustaceans

• We provide an overview of the diverse roles of small RNAs in the immune defense mechanisms of crustaceans.
• RNAi is an important component of the innate immune system of crustaceans.
• SiRNA-meditated RNAi has recently been used to validate specific gene functions; it also acts as a treatment for viral disease in crustaceans.
• There have been a few reports on the roles of miRNA in crustacean innate immunity.

Small RNAs, 21–24 nucleotides in length, are non-coding RNAs found in most multicellular organisms, as well as in some viruses. There are three main types of small RNAs including microRNA (miRNA), small-interfering RNA (siRNA), and piwi-interacting RNA (piRNA). Small RNAs play key roles in the genetic regulation of eukaryotes; at least 50% of all eukaryote genes are the targets of small RNAs. In recent years, studies have shown that some unique small RNAs are involved in the immune response of crustaceans, leading to lower or higher immune responses to infections and diseases. SiRNAs could be used as therapy for virus infection. In this review, we provide an overview of the diverse roles of small RNAs in the immune defense mechanisms of crustaceans.