Kalika Kuhar

Purification and characterization of trypsin inhibitor from Cicer arietinum L. and its efficacy against Helicoverpa armigera

Protease inhibitors in legumes are one of the most promising weapons that confer resistance against insects by inhibiting proteases present in the gut of insect larvae. In the present study, trypsin inhibitor activity was detected in the seed flour extracts of 10 selected varieties of chickpea. The presence of inhibitor was confirmed by dot blot analysis. All the varieties showed inhibitory activity in vitro against the gut protease of Helicoverpa armigera (HGP). Trypsin inhibitor has been purified to near homogeneity to 60.46 fold and 29.20% recovery from chickpea seeds using heat denaturation, ammonium sulphate fractionation, DEAE-Sephadex A-25 and Sephadex G-75. The purified inhibitor showed a single band on SDS-PAGE corresponding to molecular mass of 30,000 Da. The purified inhibitor was active over a wide pH range although it retained maximum activity between pH 6 and 10. The inhibitor protein was stable up to 80°C but retained only 40% of activity when heated at 100°C for 20 min. The inhibitor lost its activity completely at 121°C. The chickpea trypsin inhibitor exhibited inhibitory activity against Helicoverpa armigera both in vitro and in vivo. In insect bioassay, a progressive decline in larval weight, growth and survival as well as temporal extension of larval growth was observed after feeding H. armigera larvae on diet supplemented with increasing concentrations of chickpea trypsin inhibitor. The adult emergence was also adversely affected by the inhibitor. It may be concluded that chickpea trypsin inhibitor has insecticidal potential against H. armigera.

Isolation and in silico characterization of cDNA encoding cyclophilin from etiolated Vigna mungo seedlings

A full-length cDNA clone encoding cyclophilin gene of 848 bp, including a 519 bp open reading frame, has been isolated from the cDNA library constructed from etiolated seedlings of Vigna mungo (GenBank FN668732). The cDNA sequence showed 97% identity with Vigna radiata cyclophilin mRNA. The sequence was GC rich and lacked introns. The open reading frame encoded 172 amino acid polypeptide with molecular weight 18.3 kDa and theoretical pI 8.61. BlastP analysis indicated that its putative amino acid sequence shared 100% identity with several plant cyclophilins particularly legumes. The conserved seven amino acid residues region in V. mungo cyclophilin was RSGKPLH (present in legumes) instead of KSGKPLH, indicating its similarity to the cyclophilins of other legumes. This novel V. mungo cyclophilin gene will broaden the pool of plant cyclophilin genes for further studies.