Coexpression of potato type I and II proteinase inhibitors gives cotton plants protection against insect damage in the field

Abstract

Potato type I and II serine protease inhibitors are produced by solanaceous plants as a defense mechanism against insects and microbes. Nicotiana alata proteinase inhibitor (NaPI) is a multidomain potato type II inhibitor (pin II) that is produced at high levels in the female reproductive tissues of the ornamental tobacco, Nicotiana alata. The individual inhibitory domains of NaPI target the major classes of digestive enzymes, trypsin and chymotrypsin, in the gut of lepidopteran larval pests. Although consumption of NaPI dramatically reduced the growth and development of a major insect pest, Helicoverpa punctigera, we discovered that surviving larvae had high levels of chymotrypsin activity resistant to inhibition by NaPI. We found a potato type I inhibitor, Solanum tuberosum potato type I inhibitor (StPin1A), was a strong inhibitor of the NaPI-resistant chymotrypsin activity. The combined inhibitory effect of NaPI and StPin1A on H. armigera larval growth in the laboratory was reflected in the increased yield of cotton bolls in field trials of transgenic plants expressing both inhibitors. Better crop protection thus is achieved using combinations of inhibitors in which one class of proteinase inhibitor is used to match the genetic capacity of an insect to adapt to a second class of proteinase inhibitor.chymotrypsin | resistance | Lepidoptera

Mechanisms of plant defense against insect herbivores

“…61 Insecticidal properties of Galanthus nivalis L. agglutinin (GNA) were the first plant lectin shown to be active against hemipteran insects. lepidopteran, 75 and hemipteran insects. 76 The success of transgenic crops in expressing PIs against insect pests has accentuated the need to understand the mechanisms, and interactions of multiple PIs with other defenses, and the adaptive responses of the herbivores.…”

Biotechnological Approaches for the Control of Insect Pests in Crop Plants

“…More recently, the response of Helicoverpa larvae to ingestion of NaPI has been more thoroughly characterized. Following ingestion of NaPI, all surviving Helicoverpa punctigera larvae produced high levels of a chymotrypsin that was resistant to inhibition by NaPI [199]. However this NaPI-resistant chymotrypsin was strongly inhibited by a potato type 1 inhibitor which is also produced by solanaceous plants, but belongs to a different class of serine proteinase inhibitors.…”

“…Transgenic cotton plants expressing both PI classes, NaPI and StPin1A performed better than transgenic cotton plants expressing either PI alone. The improved performance of the transgenic cotton plants with both PIs was measured by an increase in cotton boll number per plant and increased yield of lint at the end of the cotton growing season ( Figure 5) [199]. …”

“…Larval and pupal weights reduced; developmental abnormalities [31] Cotton Helicoverpa armigera A higher number of cotton bolls were recorded in plants expressing NaPI and a PotI inhibitor from potato, StPin1A [199]. [200] This table lists plant and non-plant serine protease inhibitors expressed in transgenic plants that have been tested in bioassays with lepidopteran larvae.…”

“…Day 11, the % average weights compared to casein control are shown with representative larvae from each treatment (adapted from [199]) This laboratory result was then translated to transgenic plants in the field. Transgenic cotton plants expressing both PI classes, NaPI and StPin1A performed better than transgenic cotton plants expressing either PI alone.…”