Evidence for two vitellogenin‐related genes in Leucophaea maderae: The protein primary structure and its processing

Abstract

We previously reported a cDNA for vitellogenin (Vg) from the cockroach, Leucophaea maderae (Lm). In the present study, we identified another cDNA encoding a second Vg (Vg2) having stretches of amino acid sequences different from the first one, Vg1, reported earlier. The complete nucleotide sequence of Vg2 consisted of 5,915 bp, which encoded a primary protein of 1,911 residues including a 16-residue putative signal peptide. The regions different in both Vg precursors (Pro-Vg1 and pro-Vg2) were four in number, and two, relatively longer, existed at the carboxy terminal. The presence of two Vg-related cDNAs was confirmed by sequencing of RT-PCR products generated using primers designed based on the common sequences flanking the regions different in amino acid sequences. Both forms were transcribed since they could be amplified on mRNA from fat bodies of different individual females. Southern blot analysis of digested genomic DNA revealed the existence of two Vg-related genes in L. maderae indicating that each Vg cDNA originated from a separate gene. Also, the immunoblot analysis using antibodies generated against peptides unique to both Vg1 and Vg2 probed the same antigen in the same individual, suggesting LmVg to be a product coded by two different Vg precursors. Both Vg primary products showed 96% similarity at an amino acid level. Compared to other insect Vgs, Vg2 showed a slightly higher (1-2%) similarity than Vg1. We previously reported, based on amino-terminal sequence analysis, that L. maderae pro-Vg was cleaved into four subunit polypeptides (112-, 100-, 92-, and 55-kD), which were deposited in the egg as four respective vitellin (Vn) polypeptides. We show now based on immunoblot analysis that the 112-kD polypeptide is further cleaved, near the C-terminus, to an 87-kD polypeptide before it is secreted into the hemolymph. Both the L. maderae Vgs were compared with each other and with other insect Vgs and the processing pattern is discussed.

Variable induction of vitellogenin genes in the varroa mite, Varroa destructor (Anderson & Trueman), by the honeybee, Apis mellifera L, host and its environment

“…One alteration of this model is found in hemimetabolous insects where the Vgs contain multiple K/RXXR cleavage sites that lead to processing resulting in the production of several subunits of varying molecular weights that associate as vitellogenin. Although multiple sites were identified, it was apparent that only a limited number of K/RXXR sites were cleaved to produce large subunit fragments that associated as Vgs in the American cockroach, Periplaneta americana L. (Blattodea: Blattidae) (Tufail et al, 2000(Tufail et al, , 2001 and Leucophaea maderae (Blattodea: Blaberoidea) (Tufail & Takeda, 2002;Tufail et al, 2007).…”

“…Vgs also have conserved residues GI/LCG in the C-terminus region, which appear to be involved in oligomerization of the protein (Thompson et al, 2007;Khalil et al, 2011). Additionally, arthropod Vgs have one to several protease cleavage sites K/RXXR that result in proteolytic cleavage of the nascent polypeptide into two to several subunits (Barr et al, 1991;Takahashi et al, 1994;Rouille et al, 1995;Denault & Leduc, 1996;Tufail et al, 2007). The only exceptions are the insects of the order Apocrita, which lack cleavage sites in the Vgs and produce single large proteins.…”

Duplication, concerted evolution and purifying selection drive the evolution of mosquito vitellogenin genes

“…Among the six Vtg genes ( Vit-1 to Vit-6 ) of the nematode Caenorhabditis elegans , high sequence identity was observed between Vit-1 and Vit-2 (95% nt identity) and among Vit-3 , Vit-4 and Vit-5 (above 96%), while Vit-3 and Vit-4 are located in tandem on the X chromosome and are nearly identical to each other in the coding region [33]. Two Vtg genes located at different loci were identified from the cockroach Leucophaea maderae which shared high similarity (96% identity at the amino acids level) [34]. In vertebrates, four Vtg genes have been identified from the frog Xenopus laevis which fall into two pairs that share approximately 95% sequence identity within pairs, while approximately 65.5% identity between pairs [1].…”

Regulation of vitellogenin genes in insects

“…We have characterized both at biochemical and molecular levels two Vg genes each of the two cockroach species, Periplaneta americana (L.) and L. maderae (Tufail et al . , , , ; Tufail & Takeda , ). Multiple Vg genes have also been sequenced from other insect species including Locusta migratoria (R and F) (Wyatt et al .…”