Elucidation of structural and functional integration of a novel antimicrobial peptide from Antheraea mylitta.

We report here the amino acid sequence of an antimicrobial peptide of Antheraea mylitta (peptide fraction II) effectively killed urinary tract associated MDR E. coli (Dutta et al., 2016), as Gly-Gly-Gly-Gly-Gly-Gly-His-Leu-Val-Ala. The physicochemical and biological properties of this peptide were evaluated by computational analysis and its isoelectric point, grand average of hydropathicity and Boman index values were found to be 6.74, 0.42 and -1.17kcal/mol, respectively. One valid model of peptide fraction II was constructed, that contains two antiparallel ß sheets with a hairpin and appeared as 'U' shaped structure. The glycine rich composition (Gly1, Gly5, Gly6 and Ala10) facilitates mostly for its flexibility or dynamicity, and in its other wing, aggregation prone residues (Leu8, Val9, Ala10) triggered its auto-aggregations when contacted only with the microbial membrane. We employed simulation of peptide binding on the membrane, showed stable and deep insertion of peptide fraction II into the membrane through its hydrophobic tail (up to 3.3±1.46Å). Molecular docking study with Patchdock server revealed that this peptide could interact with the lipid aliphatic chain of 1-palmitoyl-2-oleoyl-phosphoethanolamine (POPE) bilayer and may linked to membrane distortion as we have reported earlier. Further, the studied peptide has been predicted not to exhibit any antigenicity and non-responsive to RBC membrane. These data for the first time provide new insights of an antimicrobial peptide from silkworm A. mylitta and it may serve as the template for the design of novel peptide antibiotics from this group of insect against MDR Gram-negative bacteria.

Induction of nodD Gene in a Betarhizobium Isolate, Cupriavidus sp. of Mimosa pudica, by Root Nodule Phenolic Acids.

A range of phenolic acids, viz., p-coumaric acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, protocatechuic acid, caffeic acid, ferulic acid, and cinnamic acid have been isolated and identified by LC-MS analysis in the roots and root nodules of Mimosa pudica. The effects of identified phenolic acids on the regulation of nodulation (nod) genes have been evaluated in a betarhizobium isolate of M. pudica root nodule. Protocatechuic acid and p-hydroxybenzoic acid were most effective in inducing nod gene, whereas caffeic acid had no significant effect. Phenylalanine ammonia lyase, peroxidase, and polyphenol oxidase activities were estimated, indicating regulation and metabolism of phenolic acids in root nodules. These results showed that nodD gene expression of betarhizobium is regulated by simple phenolic acids such as protocatechuic acid and p-hydroxybenzoic acid present in host root nodule and sustains nodule organogenesis.

Identification of RAPD and SCAR markers associated with yield traits in the Indian tropical tasar silkworm Antheraea mylitta drury.

The tropical tasar silkworm, Antheraea mylitta, is a semi-domesticated vanya silk-producing insect of high economic importance. To date, no molecular marker associated with cocoon and shell weights has been identified in this species. In this report, we identified a randomly amplified polymorphic DNA (RAPD) marker and examined its inheritance, and also developed a stable diagnostic sequence-characterized amplified region (SCAR) marker. Silkworms were divided into groups with high (HCSW) and low (LCSW) cocoon and shell weights, and the F(2) progeny of a cross between these two groups were obtained. DNA from these silkworms was screened by PCR using 34 random primers and the resulting RAPD fragments were used for cluster analysis and discriminant function analysis (DFA). The clustering pattern in a UPGMA-based dendogram and DFA clearly distinguished the HCSW and LCSW groups. Multiple regression analysis identified five markers associated with cocoon and shell weights. The marker OPW16(905 bp) showed the most significant association with cocoon and shell weights, and its inheritance was confirmed in F(2) progeny. Cloning and sequencing of this 905 bp fragment showed 88% identity between its 134 nucleotides and the Bmc-1/Yamato-like retroposon of A. mylitta. This marker was further converted into a diagnostic SCAR marker (SCOPW 16(826 bp)). The SCAR marker developed here may be useful in identifying the right parental stock of tasar silk-worms for high cocoon and shell weights in breeding programs designed to enhance the productivity of tasar silk.