**3. Results**

#### *3.1. PmMKK4 Sequence Analysis*

The mitogen-activated protein kinase kinase 4 (Pm*MKK4*) cDNA of *P. monodon* was obtained by cloning. The full-length was 1582 bp, the GenBank accession number: MN909956, and the 5 and 3 non-coding regions (UTRs) were 567 bp and 157 bp, respectively; the open reading frame (ORF) was 858 bp long and encoded 285 amino acids (Figure 1). ExPASy ProtParam predicted a molecular weight of 32.87 kD and a theoretical isoelectric point of 6.46. It was predicted that *PmMKK4* would have a total of 22 phosphorylation sites, including 15 serine sites, 4 threonine sites, and 3 tyrosine sites. In addition, the predicted results showed that *PmMKK4* had no glycosylation site, no signal peptide, and no transmembrane structure. *PmMKK4* contained a conserved serine/threonine protein kinase (S–I–A–K–T) region, which is a characteristic kinase domain for MKKK phosphorylation.
