Transgenic elite indica rice plants expressing CryIAc ∂-endotoxin of Bacillus thuringiensis are resistant against yellow stem borer ( Scirpophaga incertulas )

Abstract

Generation of insect-resistant, transgenic crop plants by expression of the insecticidal crystal protein (ICP) gene of Bacillus thuringiensis (Bt) is a standard crop improvement approach. In such cases, adequate expression of the most appropriate ICP against the target insect pest of the crop species is desirable. It is also considered advantageous to generate Bt-transgenics with multiple toxin systems to control rapid development of pest resistance to the ICP. Larvae of yellow stem borer (YSB), Scirpophaga incertulas, a major lepidopteran insect pest of rice, cause massive losses of rice yield. Studies on insect feeding and on the binding properties of ICP to brush border membrane receptors in the midgut of YSB larvae revealed that cryIAb and cryIAc are two individually suitable candidate genes for developing YSB-resistant rice. Programs were undertaken to develop Bt-transgenic rice with these ICP genes independently in a single cultivar. A cryIAc gene was reconstructed and placed under control of the maize ubiquitin 1 promoter, along with the first intron of the maize ubiquitin 1 gene, and the nos terminator. The gene construct was delivered to embryogenic calli of IR64, an elite indica rice cultivar, using the particle bombardment method. Six highly expressive independent transgenic ICP lines were identified. Molecular analyses and insect-feeding assays of two such lines revealed that the transferred synthetic cryIAc gene was expressed stably in the T 2 generation of these lines and that the transgenic rice plants were highly toxic to YSB larvae and lessened the damage caused by their feeding.Technologies of plant cell biology and molecular biology have attracted much attention because they provide a powerful and novel means to supplement as well as complement the traditional methods of crop improvement. The transgenic approach of plant genetic engineering provides access to an unlimited gene pool for the transfer of desirable genes between any two species of interest, irrespective of their evolutionary or taxonomic relation. The successful generation of transgenic insectresistant crop plants by transferring the insecticidal crystal protein (ICP) gene of Bacillus thuringiensis (Bt; refs. 1-8), a Gram-positive, spore-forming bacterium, is one of the major breakthroughs in crop science that the new genetics has provided.indica rice is one of the most important food crops (9) of the world. There are half a dozen different species of lepidopteran insects whose larvae bore into the tissue of rice plants, and the resultant damage causes massive yield losses (10). Yellow stem borer (YSB), Scirpophaga incertulas, is most certainly the major contributor to these losses. The first-stage YSB larvae cut small holes in the stem of the paddy plant and enter the plant tissue, remaining there for the rest of their lives as larvae and pupae. The larvae feed voraciously inside the stem, providing themselves complete protection against chemical pesticides. There are no known resistance genes in rice (11) that can be rea...

The Interactions of Allium sativum Leaf Agglutinin with a Chaperonin Group of Unique Receptor Protein Isolated from a Bacterial Endosymbiont of the Mustard Aphid

“…Two-dimensional PAGE Analysis of the Receptor Protein-The electroeluted proteins were additionally separated by two-dimensional gel electrophoresis in a Bio-Rad Mini-Protean II Isoelectric focusing unit using carrier ampholytes (3)(4)(5)(6)(7)(8)(9)(10) according to the protocol given by the manufacturer. For the second dimension, gels were run in a MiniProtean III SDS-PAGE module.…”

“…Control of aphids using transgenic plants has been suggested as an alternative to pesticide spray. To date, the only commercial insect-resistant transgenic plants are those expressing genes from the soil bacterium Bacillus thuringiensis encoding insecticidal crystal proteins (Bt-toxins) (5)(6)(7)(8)(9)(10). Aphids, including L. erysimi, are not affected by Bt toxins.…”

Strategies for developing Green Super Rice

“…The most commonly used Bt genes in transgenic crops including rice are Cry1Ab, Cry1Ac, and a fusion gene of Cry1Ac/Cry1Ab or Cry1Ab/c (19)(20)(21)(22)(23)(24)(25)(26)(27)(28). However, binding tests of midgut brush border membrane vesicles showed that Cry1Aa, Cry1Ab, and Cry1Ac toxins share a common binding site (29)(30)(31); thus, a mutant that is able to overcome one of the Cry1A genes is also likely to be resistant to other Cry1A genes as well.…”

Recent Advances in Transgenic Rice Research Technology

“…There are different reports, in which Bacillus thuringiensis (Bt)-derived genes namely Cry genes have been introduced in rice against insect resistance via different methods of gene delivery electroporation (Fujimoto., 1993), biolistic method (Wunn et al, 1996;Nayak et al, 1997;Ghareyazie 1997;Alam et al, 1998;Datta et al, 1998;Alam et al, 1999); and by Agrobacterium method (Cheng et al, 1998). Fujimoto et al, (1993) were the first to successfully generate the insect-resistant transgenic rice by transferring modified cry1Ab gene from Bacillus thuringiensis.…”