Molecular characterization of a c-type lysozyme from the desert locust, Schistocerca gregaria (Orthoptera: Acrididae)

Abstract

Lysozymes are bacteriolytic peptides that are implicated in the insect nonspecific innate immune responses. In this study, a full-length cDNA encoding a c-type lysozyme from Schistocerca gregaria (SgLys) has been cloned and characterized from the fat body of immune-challenged 5(th) instar. The deduced mature lysozyme is 119 amino acid residues in length, has a calculated molecular mass of 13.4 kDa and an isoelectric point (Ip) of 9.2. SgLys showed high identities with other insect lysozymes, ranging from 41.5% to 93.3% by BLASTp search in NCBI. Eukaryotic in vitro expression of the SgLys ORF (rSgLys) with an apparent molecular mass of ∼16 kDa under SDS-PAGE is close to the calculated molecular weight of the full-length protein. rSgLys displayed growth inhibitory activity against Gram-negative and Gram-positive bacteria. 3D structure modeling of SgLys, based on comparison with that of silkworm lysozyme, and sequence comparison with the helix-loop-helix (α-hairpin) structure of hen egg white lysozyme (HEWL) were employed to interpret the antibacterial potencies. Phylogenetic alignments indicate that SgLys aligns well with insect c-type lysozymes that expressed principally in fat body and hemocytes and whose role has been defined as immune-related. Western blot analysis showed that SgLys expression was highest at 6-12 h post-bacterial challenge and subsequently decreased with time. Transcriptional profiles of SgLys were determined by semi-quantitative RT-PCR analysis. SgLys transcript was upregulated at the highest level in fat body, hemocytes, salivary gland, thoracic muscles, and epidermal tissue. It was expressed in all developmental stages from egg to adult. These data indicate that SgLys is a predominant acute-phase protein that is expressed and upregulated upon immune challenge.

Annotation of the Asian Citrus Psyllid Genome Reveals a Reduced Innate Immune System

“…Lysozymes are a specific group of cell wall-disrupting antimicrobial proteins that defend against bacteria and fungus found in both vertebrates and invertebrates. There are two types of lysozymes found in insects, i- and c-type, both of which have been observed to be involved in digestion and immune defenses, indicating that function is species specific or related to tissue level expression rather than associated with type (Mohamed et al, 2016). A comparison of lysozyme genes identified in D. citri with classified lysozymes in other insects indicates that two are likely c-type and one is i-type (Figure S1).…”

A Family of CSαβ Defensins and Defensin-Like Peptides from the Migratory Locust, Locusta migratoria, and Their Expression Dynamics during Mycosis and Nosemosis

“…A similar phenomenon was reported for c-type lysozymes of both Shistocerca gregaria and L . migratoria [58]. However, LmDEF5 is convergently related to the exoptergotes.…”

Molecular Characterization of a Lysozyme Gene and Its Altered Expression Profile in Crowded Beet Webworm (Loxostege sticticalis)

“…For example, when Asn 37 and Trp 62 of HEWL were replaced by Gly 33 and Tyr 59 of S . gregaria , respectively, exhibited about 2–3 fold higher bacteriolytic activity than HEWL [ 29 ]. As a matter of fact, such substitution also occurred naturally in LsLysozyme , since the sequence of LsLysozyme also contains a Gly in positon 34 and a Tyr in position 60, an enhanced bacteriolytic activity may be observed in L .…”