Taiman negatively regulates the expression of antimicrobial peptides by promoting the transcription of cactus in Macrobrachium nipponense.

In insects, Taiman (Tai) participates in the juvenile hormone, 20-hydroxyecdysone, insulin, and Hippo signaling pathways. However, the role of Tai in crustacean innate immunity is less known. In this study, four Tai isoforms (MnTai-A, MnTai-B, MnTai-C, and MnTai-D) produced by alternative splicing were identified from Macrobrachium nipponense. The obtained genome sequences indicated that MnTai DNA has more than 20 exons and 19 introns. The second to last (-exon2) and the third to last (-exon3) exons can be alternatively spliced. The loss of -exon2 or -exon3 produces MnTai-B or MnTai-C, respectively. Both exons are absent in MnTai-D. The full-length cDNA of MnTai-A (including all exons) was 6894 bp with an open reading frame of 4998 bp that encoded a protein of 1665 amino acids. MnTaiA contains the conservative structure of the Tai family and clustered with nuclear receptor coactivator from shrimp. All these four isoforms were widely distributed in a variety of tissues with the highest expression level in the hepatopancreas except MnTaiC. The transcriptional levels of total Tai genes (designated as MnTaiT) in the hepatopancreas and gills were regulated by bacterial or viral challenge. Knockdown of MnTaiT increased the expression of anti-microbial peptides (AMPs) during Vibrio parahaemolyticus infection. Further study indicated that the negative regulation of AMP gene expression by prawn Tai was mediated through its positive regulation of cactus. Our research provides valuable information that prawn Tai isoforms are involved in innate immunity.