Tryptophan Decarboxylase, Tryptamine, and Reproduction of the Whitefly

Abstract

Tryptophan decarboxylase (TDC) from Cafharanfhus roseus (periwinkle) converts tryptophan to the indole-alkaloid tryptamine. When the TDC gene was expressed in transgenic tobacco, the 55-kD TDC enzyme and tryptamine accumulated. Bemisia fabaci (sweetpotato whitefly) reproduction on transgenic plants decreased up to 97% relative to controls. Production of tryptamine, its derivatives, or other products resulting from TDC activity may discourage whitefly reproduction and provide a single-gene-based plant protection strategy.The process by which insects select a host plant for feeding and reproduction begins with the sensing of structural and metabolic components of the plant. Alkaloids are one of several plant-produced substances known to greatly influence insect recognition, feeding, and oviposition. Levels of the alkaloid gramine are inversely related to the extent of aphid infestation (ZuAiga et al., 1988). Furthermore, polyphagous aphids colonize only low-alkaloid-producing plants, whereas aphids with restricted host specificity prefer high-alkaloid producers, using the ingested alkaloids in their own defense (Niemeyer, 1990).It has been difficult to examine how alkaloids affect insect feeding, because to do so host plant lines must differ only in alkaloid content. Testing alkaloids in an artificial insect diet provides some information, but not a11 behavioral aspects of plant-insect interactions in situ can be reproduced exactly.To directly assess insect feeding on alkaloid-containing plants, we transferred and expressed in Nicotiana tabacum (tobacco) the gene encoding the TDC enzyme (EC 4.2.1.27) of Catharantkus Yoseus (L.) (periwinkle). In several species with TDC activity (Robinson, 1979), tryptamine is thought to participate in the protection of young seedlings against insects, particularly in newly emergent seedling stems and

Antibiosis‐type insect resistance in transgenic plants expressing a teratocyte secretory protein (TSP14) gene from a hymenopteran endoparasite (Microplitis croceipes)

“…Bacillus thuringiensis, Vaeck et al, 1987). Transgenic approaches have also been used to introduce other insecticidal genes into plants such as inhibitors of digestive enzymes (Hilder et al, 1987;Huesing et al, 1991), resistance genes from plants (Dowd et al, 1998;Felton et al, 1992), and micro-organisms (Cho et al, 1995;Estruch et al, 1996;Vaeck et al, 1987;Warren et al, 1996), lectin genes (Cavalieri et al, 1995;Chrispeels and Raikhel, 1991), tryptophan decarboxylase (Thomas et al, 1995), and chitinases (Gatehouse et al, 1996) for the purpose of controlling insect herbivores (recently reviewed by Schuler et al, 1998, and references therein). However, parasitoid genes have not, previously, been expressed in transgenic plants for insect control.…”

Levels of Plant Resistance in Chillies Capsicum spp against Whitefly, Bemisia tabaci

“…These compounds could be present in the leaf mesophyll or they can be released as volatiles that could play a role as a repellent or antibiotic substance to herbivores (Antonious and Kochhar 2003;Chermenskaya et al, 2009). Thomas et al, (1995) observed that, when the tryptophan decarboxylase (TDC) gene (isolated from Cantharanthus roseus (periwinkle) when expressed in transgenic tobacco, the 55-kD TDC enzyme and tryptamine accumulated had caused 97% reduction in B. tabaci reproduction. Production of tryptamine, its derivatives, or other products resulting from TDC activity may discourage whitefly reproduction (Thomas et al, 1995).…”

“…Thomas et al, (1995) observed that, when the tryptophan decarboxylase (TDC) gene (isolated from Cantharanthus roseus (periwinkle) when expressed in transgenic tobacco, the 55-kD TDC enzyme and tryptamine accumulated had caused 97% reduction in B. tabaci reproduction. Production of tryptamine, its derivatives, or other products resulting from TDC activity may discourage whitefly reproduction (Thomas et al, 1995).…”

Towards the transformation of onions(Allium cepa)

“…Insertion of the tryptophan decarboxylase gene from Catharanthus roseus into tobacco has been shown to reduce whitefly (Bemisia tabacii) emergence by 98.5% compared to nontransgenic controls (Thomas et al 1994). Such systems may be effective against thrips on onions.…”