Aquaculture America 2020

February 9 - 12, 2020

Honolulu, Hawaii

CHARACTERIZATION OF NK-LYSIN ANTIMICROBIAL PROTEIN GENES, AND THEIR ACTIVITIES, IN RAINBOW TROUT

Brian Shepherd* , Hao Ma, Guantu  Gao, Yniv Palti, Mark McBride,  Nicole Thunes, Miles Lange, Douglas Leaman, Malathi Krishnamurthy and Gregory Wiens
USDA-ARS-School of Freshwater Sciences
University of Wisconsin-Milwaukee
600 E. Greenfield Ave.
Milwaukee, WI 53204 USA
brian.shepherd@usda.gov
 

The physiological contro l, and number, of antimicrobial peptides (AMPs)  is not well understood in finfish .   Based on the new rainbow trout genome assembly, we identified 6 new saposin-like  AMP genes in rainbow trout. Pr otein sequence alignments and in silico modeling show that the proteins encoded by those genes belong to the Nk-lysin AMP sub-family (termed: Nkl 1, 2, 3, 4 and Nkl-like a & b). Transcriptomic data show  that  expression of nkl1-nkl4  mRNAs occurred in many tissues.  By contrast, the nkl-like a & b mRNAs are mostly expressed in immune-related tissues. T he effects of  various aquaculture stressors, and a disease challenge (F. psychrophilum ; Fp) in rainbow trout, were examined using RNA sequencing . A bundances of nkl1, nkl2, nkl4, and nkl-like a were downregulated by high-temperature and salinity stress, and nkl3 and nkl-like b were downregulated by high-temperature. In the Fp challenge study, abundances of nkl3, nkl4, nkl-like a and nkl-like b, were significantly affected by genetic line (resistant vs non-resistant) and treatment (PBS or Fp), which were further verified by qRT- PCR with spleen tissue sampled at 4 post-challenge time points (0 - 144 h). This work represents an initial characterization of these Nkl proteins in rainbow trout, with ongoing in vitro  work to  characterize how these AMPs  affect flavobacterial pathogens, their biofilms, and  survival and replication of novirhabdoviral pathogens .  Understanding the distribution,  regulation  and bioactivity of these AMPs may enable rational design of approaches to reduce infectious disease in commercial aquaculture.