Enhanced Resistance to Helicoverpa zea in Tobacco Expressing an Activated Form of Maize Ribosome- Inactivating Protein

Abstract

Progeny of two transgenic tobacco (Nicotiana tabacum L.) lines that expressed an activated form of maize (Zea mays L.) ribosome-inactivating protein (RIP) had varying resistance to the insect species tested. A subset of R(2) plants from the two lines appeared to be more resistant to larvae of the cigarette beetle, Lasioderma serricorne (F.), and the tobacco hornworm, Manduca sexta (L.) than the wild type plants. Progeny (R(3)) of the more resistant R(2) plants were tested more extensively for insect resistance. Resistance to the corn earworm, Helicoverpa zea (Boddie), was most consistent, with significantly decreased feeding often accompanied by increased mortality and reduced weights of survivors fed on leaf disks of the two transgenic lines compared to the wild type. The amount of damage by H. zea was significantly inversely correlated with levels of RIP. Resistance of RIP-producing plants to H. zea was greater than expected on the basis of prior in vitro results using diet-incorporated maize RIP. The R(3) transgenic plant leaf disks were also often more resistant to feeding by larvae of L. serricorne compared to wild type plants. Although reduced feeding by M. sexta was noted when they were fed leaf disks from transgenic compared to wild type plants the first day of exposure, differences were not significant. This information provides further support for maize RIP having a role in resistance to maize-feeding insects.

Differential resistance of switchgrass Panicum virgatum L. lines to fall armyworms Spodoptera frugiperda (J. E. Smith)

“…Ten newly hatched larvae were added to each dish. The degree of feeding was determined by visually counting the number of 0.25 and 1.0 mm 2 holes or equivalent daily (Dowd and Lagrimini 1997, Dowd et al 2003, 2007a. Larval mortality was also determined daily during the 2-day assays.…”

Expression of Sambucus nigra agglutinin (SNA-I′) from elderberry bark in transgenic tobacco plants results in enhanced resistance to different insect species

“…Insecticidal activity of type-2 RIPs has been demonstrated towards some insects (Gatehouse et al 1990;Dowd et al 1998Dowd et al , 2003Wei et al 2004). Although the enzymatic mechanism of RIP activity is well defined, the physiological steps by which ribosome inactivation leads to cell death are not well understood.…”

Entomotoxic action of Sambucus nigra agglutinin i in Acyrthosiphon pisum aphids and Spodoptera exigua caterpillars through caspase‐3‐like‐dependent apoptosis

“…Recently, Dowd et al (2006) have shown significant feeding reduction and larval mortality in two Lepidopteran species (Helicoverpa zea and Trichoplusia ni) by feeding on transgenic tobacco plants expressing maize RIP. In previous studies, these authors also reported significant mortality caused by maize RIP in the beetles Lasioderma serricorne and Carpophilus freemani (Dowd et al, 1998(Dowd et al, , 2003. RIPs from seeds of dicot plants, such as castor bean (Ricinus communis), soapwort (Saponaria officinalis) and bitter gourd (Momordica cochinchinensis), were shown to be toxic toward beetles but not caterpillars (Gatehouse et al, 1990).…”

“…In these in planta experiments, beet armyworm caterpillars were strongly affected in their survival, whereas aphids were affected less with sublethal effects on progeny and population build up (ShahidiNoghabi et al, 2008). It has been reported before by Dowd et al (2003) that the entomotoxicity of the maize RIP to Helicoverpa and Lasioderma is higher in a leaf assay with transgenic tobacco overexpressing the maize RIP than in a bioassay where insects were fed on an artificial diet dosed with maize RIP.…”