Identification, Annotation and Comparative Analysis of Cytoglobin and Neuroglobin Genes from Gill Transcriptome of Three Freshwater Crayfish

Abstract

Neuroglobin and cytoglobin, both proteins bind oxygen reversibly and involve in cellular oxygen homeostasis. We identified and annotated all these genes from gill transcriptome of three commercially important freshwater crayfish, Cherax quadricarinatus, C. destructor and C. cainii. The sequences were made publicly available to NCBI GenBank except C. quadricarinatus, But data was submitted in NCBI. Comparative molecular analysis of these genes across the species were also carried out . The cytoglobin obtained from the species Cherax quadricarinatus, C. destructor and C. cainii were named as CqCygb, CdCygb and CcCygb; and neuroglobin named as CqNgb, CdNgb and CcNgb respectively. The deduced proteins encoded by CqCygb, CdCygb and CcCygb contained 190 amino acids; and those encoded by CqNgb, CdNgb and CcNgb were 209 aa. Cygb obtained from our study shared high similarity with Cygbs from Carcinus maenas (70% identity), Penaeus vannamei (62% identity) and Hyalella Azteca (52% identity) and Ngb shared similarity with Ngbs from, Microplitis demolitor (63% identity), Penaeus vannamei (80% identity). Neuroglobin and cytoglobin are highly conserved, displaying very low levels of non-synonymous nucleotide substitutions. A total of 9 nonsynonymous mutation (amino acid replacement) and 20 synonymous mutations were observed in Cygbs from three crayfish species, while 10 nonsynonymous mutation and 40 synonymous mutation were found in Ngbs across the species. However, all the changes were outside the functional sites. Cygb is more conserve than Ngb. Findings of the study will assist in further molecular analysis and gene expression study.