Functional and evolutionary implications from the molecular characterization of five spermatophore CHH/MIH/GIH genes in the shrimp Fenneropenaeus merguiensis
March
Functional and evolutionary implications from the molecular characterization of five spermatophore CHH/MIH/GIH genes in the shrimp Fenneropenaeus merguiensis
LiLi Shi☯ 0 2 3
Bin Li☯ 0 2 3
Ting Ting Zhou 0 2 3
Wei Wang 0 2 3
Siuming F. Chan 0 2 3
0 Fisheries College, Guangdong Ocean University , Zhanjiang , PR China
1 31572606) to SMC and a Ph.D. Start Up fund of
2 Funding: This research was funded by Guangdong Ocean University (GDOU)'s University Research Enhancement Fund (Project
3 Editor: Christian Wegener , Biocenter, UniversitaÈt WuÈrzburg , GERMANY
The recent use of RNA-Seq to study the transcriptomes of different species has helped identify a large number of new genes from different non-model organisms. In this study, five distinctive transcripts encoding for neuropeptide members of the CHH/MIH/GIH family have been identified from the spermatophore transcriptome of the shrimp Fenneropenaeus merguiensis. The size of these transcripts ranged from 531 bp to 1771 bp. Four transcripts encoded different CHH-family subtype I members, and one transcript encoded a subtype II member. RT-PCR and RACE approaches have confirmed the expression of these genes in males. The low degree of amino acid sequence identity among these neuropeptides suggests that they may have different specific function(s). Results from a phylogenetic tree analysis indicated that these neuropeptides were likely derived from a common ancestor gene resulting from mutation and gene duplication. These CHH-family members could be grouped into distinct clusters, indicating a strong structural/functional relationship among these neuropeptides. Eyestalk removal caused a significant increase in the expression of transcript 32710 but decreases in expression for transcript 28020. These findings suggest the possible regulation of these genes by eyestalk factor(s). In summary, the results of this study would justify a re-evaluation of the more generalized and pleiotropic functions of these neuropeptides. This study also represents the first report on the cloning/identification of five CHH family neuropeptides in a non-neuronal tissue from a single crustacean species.
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Data Availability Statement: All relevant data are
within the paper and its Supporting Information
files.
Introduction
The X-organ sinus gland complex of the crustacean eyestalk is known to produce many important
neuropeptides that control important, diversified physiological processes [1±3]. Although the
redpigment concentrating hormone (RPCH) and the pigment concentrating hormone of the
chromatotrophins were the first group of neuropeptides to be fully characterized [
4
], the crustacean
hyperglycemic hormone (CHH), molt inhibiting hormone (MIH) and gonad inhibiting hormone (i.e.,
the National Science Foundation of the Guangdong
Province, China (# 2016A030310334) to LLS. The
funders had no role in study design, data collection
and analysis, decision to publish, or preparation of
the manuscript.
CHH/MIH/GIH neuropeptides) have attracted much research attentions [5±7] because of their
potential use in improving the aquaculture of many economically valuable species. They are the
most popular group of crustacean neuropeptides examined so far. At present, a large amount of
research efforts has focused on the study of CHH family neuropeptides. However, we still know
very little about this group of important neuropeptides. One of the reasons is the lack of concerted
and focused study on this group of neuropeptides in a single species. Furthermore, there are still
many unidentified members in a single species. Due to their economic importance, there are much
information on the CHH neuropeptides in shrimps [
5, 8, 9
]. Because of the structural similarity of
the CHH-family members, they are often known to have overlapping functions. For example, in
the crayfish Procambarus clarkii, CHH is involved in both regulation of circulating glucose levels
and inhibition of ecdysteroid synthesis [
10
]. The molt inhibiting hormone of the shrimp
Metapenaeus ensis (MeMIH-B) has also been shown to have gonad-stimulating properties [
6, 11
]. At
present, there are >100 eyestalk neuropeptide cDNAs identified from different crustaceans. However,
it is confusing that the current naming and identification of CHH members have been restricted to
only a few that depend mainly on their similarity with other species. Most of the studies focus on
the molecular characterization of cDNA, but only a few functional analyses (<10% of those
identified cDNA) have been performed for purified neuropeptides or recombinant protein of these
cDNAs. Therefore, functional annotation of most of these cDNAs are inaccurate as the naming of
these neuropeptides in most species is based on sequence similarity. Without identifying all the
members of this gene family, it would certainly lead to mislabeling of gene names.
Initially, the expression of CHH family neuropeptide was thought to be restricted to the
eyestalks (...truncated)