Characterization of two runt genes (MnRunt1, MnRunt2) and their regulation of prophenoloxidase-related genes expression in Macrobrachium nipponense

Abstract

Runt-related transcription factors (RUNX) exist in vertebrates and invertebrates and play critical roles in development, metabolism, and diseases. Runt is a kind of RUNX. In this study, two Runt genes were cloned from the oriental river prawn Macrobrachium nipponense, named MnRunt1 and MnRunt2. The coding region of MnRunt1 is 1302 bp, encoding a protein of 433 amino acids. The full-length cDNA sequence of the MnRunt2 gene is 2498 bp, including an open reading frame of 1536 bp encoding 511 amino acids. MnRunt2 produces another seven isoforms by alternative splicing. MnRunt1 and MnRunt2 both contain a Runt domain. Phylogenetic tree analysis showed that MnRunt1 and MnRunt2 are located in two different clades. MnRunt1 and MnRunt2 are widely distributed in all tested tissues and highly expressed in the hepatopancreas of M. nipponense. The expression levels of MnRunt1 and MnRunt2 in the hemocytes of M. nipponense are upregulated at various levels at multiple time points after infection with Vibrio parahaemolyticus or Staphylococcus aureus. The expression levels of clip domain serine protease 1 (MncSP1), MncSP1-isoform, MncSP2, SP homolog (MnSPH), and phenoloxidase (MnPO) are inhibited in MnRunt1 or MnRunt2 knockdown prawns with V. parahaemolyticus or S. aureus challenge. Moreover, the survival rate of prawns is significantly reduced after MnRunt1 or MnRunt2 knockdown. Therefore, it can be speculated that MnRunt1 and MnRunt2 are involved in the innate immune defense of M. nipponense by regulating the expression of genes related to the prophenoloxidase pathway.