Purification and evaluation of antiviral proteins from Bougainvillea x buttiana against Helicoverpa armigera

Abstract

An open reading frame (ORF) of cDNA encoding 35.49 kDa ribosome-inactivating/antiviral protein (RIP/AVP) from the leaves of Bougainvillea x buttiana cv Mahara, was cloned into an expression vector and expressed in Escherichia coli as a simple protein. The recombinant protein, designated as BBAP1, was tested for its insecticidal activity against Helicoverpa armigera (Hübner)(Lepidoptera: Noctuiidae) – the most important insect-pest in agriculture. Initially, to appreciate the insecticidal activity, water extract of B. ×buttiana leaves (1: 10; w/v) was assayed against 5-day old larvae of the test-insect with intoxicated natural diet (Frenchbean pods). Larval mortality never exceeded 50% in the test-concentrations (maximum, 1: 1 ratio of extract and water). For testing BBAP1, wheat-germ-based artificial diet was taken in the diet-surface incorporation assay. Neonates of the target insect were reared on the intoxicated diet at three dosages, viz 0.127, 1.27 and 12.7 ng/g diet, till eclosion and oviposition by the emerged and mated adult moths. Growth and development as affected by BBAP1 is discussed in this pursuit. Growth and developmental indices for highest dosage were 2.23, 2.52 as against 5.6, 3.3 and 4.21, 3.16 in the control and buffer blank populations, respectively. Toxicity of the said AVP even at nanogram levels like those in Bacillus thuringiensis (Bt) insecticidal crystal proteins (ICP), implies that BBAP1 has the potential to be used in frontier plant-protection technology in particular the insectresistant transgenics.