Downregulation of Chilo suppressalis alkaline phosphatase genes associated with resistance to three transgenic Bacillus thuringiensis rice lines
18
Citation
38
Reference
10
Related Paper
Citation Trend
Abstract:
Abstract Insecticidal crystal (Cry) proteins produced by the bacterium Bacillus thuringiensis are highly toxic to lepidopteran pests. Strains of transgenic rice expressing cry genes have been developed that are resistant to rice pests. Understanding the mode of action of Cry toxins in rice pests will improve our ability to use them effectively as insecticides. In this study, we tested the hypothesis that alkaline phosphatases (ALPs) are involved in Cry1A, Cry2Aa and Cry1Ca toxicity in Chilo suppressalis , an important insect pest of rice crops in China. We first cloned three novel C . suppressalis alps ( Csalps ) from the larval midgut of C . suppressalis . RNA interference knockdown of six different Csalp genes ( Csalp1 , Csalp2 , Csalp3 , Csalp4 , Csalp5 and Csalp6 ) showed that knockdown of three of these, Csalp1 , Csalp2 and Csalp4 , reduced larval mortality to the transgenic rice strain TT51, which expresses a fusion protein of Cry1Ab and Cry1Ac, whereas suppression of Csalp1 , Csalp2 , Csalp3 , Csalp4 and Csalp6 transcripts decreased the susceptibility of larvae to the transgenic rice strain T2A‐1, which expresses cry2Aa . Moreover, downregulation of Csalp1 , Csalp2 , Csalp3 , Csalp4 and Csalp5 transcripts conferred significant tolerance to the transgenic rice strain T1C‐19, which expresses cry1Ca . These results suggest that these ALPs play a key role in the toxicity of Cry1A, Cry2A and Cry1C to C . suppressalis .Keywords:
Chilo suppressalis
Bacillus thuringiensis
Genetically modified rice
Cry1Ac
Although the striped stem borer (SSB, Chilo suppressalis Walker) is a devastating pest of rice that causes significant economic losses, management options are currently limited. Plant-mediated RNA interference (RNAi) is an emerging crop protection technique in which transgenic plants are modified to express insect-specific double-stranded RNAs (dsRNAs) that trigger RNAi silencing in target pests.In this study, an RNAi-based screen of 35 candidate SSB genes identified a small heat shock protein gene (CssHsp) as a potential plant-based RNAi target. To assess its utility in planta, a total of 39 transgenic rice plants were generated, with 11 independent transformants found to contain a single copy of the dsCssHsp expression cassette. In life-time feeding bioassays, three transgenic lines (DS10, DS35, DS36) were found to have significant negative impacts on SSB populations. After feeding for 8 days, mortality in the three transgenic lines exceeded 60%. By pupation, mortality further increased to 90% and few SSB survived to eclosion. Gene expression analyses confirmed that CssHsp transcript levels were significantly reduced after feeding on the transgenic dsCssHsp rice.These results demonstrate the potential for developing a plant-mediated RNAi strategy targeting CssHsp as a more biorational field-based approach for SSB control. © 2021 Society of Chemical Industry.
Chilo suppressalis
Genetically modified rice
RNA Silencing
Genetically modified maize
Cite
Citations (4)
Laboratory bioassays and field surveys were carried out to compare the resistance of three transgenic rice (Oryza sativa L.) lines including Bt-DL expressing a single gene cry1Ab, Bt-KF6 expressing stacked genes cry1Ac and CpTI genes and Bt-SY63 expressing a fusion gene cry1Ab/cry1Ac, respectively, to an important rice pest Chilo suppressalis (Walker). In addition, enzyme-linked immunosorbent assays (ELISA) were conducted to monitor the Bt protein expressions in rice leaves and stems at different rice growth stages. Results showed that all the transgenic rice lines exhibited significantly high resistance to the pest compared with their corresponding nontransformed isolines. Among the transgenic rice lines, Bt-SY63 and Bt-KF6 had higher resistance to C. suppressalis at early growth stage, but lower resistance at late stages, while the pest resistance of Bt-DL was relatively stable throughout the growing season. The results were consistent with ELISA results showing that Bt protein levels in Bt-SY63 or Bt-KF6 leaves decreased in late growth stages, but were relatively stable in Bt-DL at all growth stages. This demonstrates that the resistance to a pest by Bt plants is positively correlated with Cry protein expression levels in plant tissues. Compared with Bt-SY63 and Bt-KF6, the Bt protein expression levels were significantly lower in Bt-DL, while its resistance to C. suppressalis was the highest. This may suggest that C. suppressalis is more susceptible to Cry1Ab than to Cry1Ac. The data from the current study are valuable for decision-making for commercial use of Bt rice lines and development of appropriate pest control and resistance management strategies for the transgenic rice lines.
Chilo suppressalis
Cry1Ac
Genetically modified rice
Bt Cotton
Bacillus thuringiensis
Cite
Citations (24)
Chilo suppressalis
Cry1Ac
Bacillus thuringiensis
Cite
Citations (0)
Bacillus thuringiensis
Cry1Ac
Cite
Citations (6)
Bacillus thuringiensis
Cry1Ac
Cite
Citations (417)
ABSTRACT Four subpopulations of a Plutella xylostella (L.) strain from Malaysia (F 4 to F 8 ) were selected with Bacillus thuringiensis subsp. kurstaki HD-1, Bacillus thuringiensis subsp. aizawai , Cry1Ab, and Cry1Ac, respectively, while a fifth subpopulation was left as unselected (UNSEL-MEL). Bioassays at F 9 found that selection with Cry1Ac, Cry1Ab, B. thuringiensis subsp. kurstaki , and B. thuringiensis subsp. aizawai gave resistance ratios of >95, 10, 7, and 3, respectively, compared with UNSEL-MEL (>10,500, 500, >100, and 26, respectively, compared with a susceptible population, ROTH). Resistance to Cry1Ac, Cry1Ab, B. thuringiensis subsp. kurstaki , and B. thuringiensis subsp. aizawai in UNSEL-MEL declined significantly by F 9 . The Cry1Ac-selected population showed very little cross-resistance to Cry1Ab, B. thuringiensis subsp. kurstaki , and B. thuringiensis subsp. aizawai (5-, 1-, and 4-fold compared with UNSEL-MEL), whereas the Cry1Ab-, B. thuringiensis subsp. kurstaki -, and B. thuringiensis subsp. aizawai -selected populations showed high cross-resistance to Cry1Ac (60-, 100-, and 70-fold). The Cry1Ac-selected population was reselected (F 9 to F 13 ) to give a resistance ratio of >2,400 compared with UNSEL-MEL. Binding studies with 125 I-labeled Cry1Ab and Cry1Ac revealed complete lack of binding to brush border membrane vesicles prepared from Cry1Ac-selected larvae (F 15 ). Binding was also reduced, although less drastically, in the revertant population, which indicates that a modification in the common binding site of these two toxins was involved in the resistance mechanism in the original population. Reciprocal genetic crosses between Cry1Ac-reselected and ROTH insects indicated that resistance was autosomal and showed incomplete dominance. At the highest dose of Cry1Ac tested, resistance was recessive while at the lowest dose it was almost completely dominant. The F 2 progeny from a backcross of F 1 progeny with ROTH was tested with a concentration of Cry1Ac which would kill 100% of ROTH moths. Eight of the 12 families tested had 60 to 90% mortality, which indicated that more than one allele on separate loci was responsible for resistance to Cry1Ac.
Cry1Ac
Bacillus thuringiensis
Cite
Citations (161)
Cry1Ac
Bacillus thuringiensis
Strain (injury)
Cite
Citations (3)
ABSTRACT A laboratory strain (GY) of Helicoverpa armigera (Hübner) was established from surviving larvae collected from transgenic cotton expressing a Bacillus thuringiensis var. kurstaki insecticidal protein (Bt cotton) in Gaoyang County, Hebei Province, People's Republic of China, in 2001. The GYBT strain was derived from the GY strain through 28 generations of selection with activated Cry1Ac delivered by diet surface contamination. When resistance to Cry1Ac in the GYBT strain increased to 564-fold after selection, we detected high levels of cross-resistance to Cry1Aa (103-fold) and Cry1Ab (>46-fold) in the GYBT strain with reference to those in the GY strain. The GYBT strain had a low level of cross-resistance to B. thuringiensis var. kurstaki formulation (Btk) (5-fold) and no cross-resistance to Cry2Aa (1.4-fold). Genetic analysis showed that Cry1Ac resistance in the GYBT strain was controlled by one autosomal and incompletely recessive gene. The cross-resistance pattern and inheritance mode suggest that the Cry1Ac resistance in the GYBT strain of H. armigera belongs to “mode 1,” the most common type of lepidopteran resistance to B. thuringiensis toxins. A cadherin gene was cloned and sequenced from both the GY and GYBT strains. Disruption of the cadherin gene by a premature stop codon was associated with a high level of Cry1Ac resistance in H. armigera . Tight linkage between Cry1Ac resistance and the cadherin locus was observed in a backcross analysis. Together with previous evidence found with Heliothis virescens and Pectinophora gossypiella , our results confirmed that the cadherin gene is a preferred target for developing DNA-based monitoring of B. thuringiensis resistance in field populations of lepidopteran pests.
Cry1Ac
Bacillus thuringiensis
Strain (injury)
Heliothis virescens
Cite
Citations (296)
Two transgenic IR72 lines, TT9-3 and TT9-4, carrying a fused Bt gene cry1Ab/cry1Ac from Bacillus thuringiensis Berliner were field tested to evaluate their multiple resistance against four lepidoptera and their agronomic performance in Hangzhou, China, in 1999. The results demonstrated that both transgenic lines were highly resistant against natural infestation and artificial infestation of four lepidopteran species: striped stem borer (Chilo suppressalis), pink stem borer (Sesamia inferens), leaffolder (Cnaphalocrocis medinalis), and green semilooper (Naranga anescens). In contrast, the non-transformed IR72 control showed serious damage symptoms of deadhearts, whiteheads, folded leaves or leaf notches. Field performance data showed that Bt transgenic lines may provide excellent opportunity for Bt rice deployment for commercial scale in Asia.
Chilo suppressalis
Bacillus thuringiensis
Cry1Ac
Cnaphalocrocis medinalis
Bt Cotton
Genetically modified rice
Chilo
Cite
Citations (88)
Chilo suppressalis
Cry1Ac
Bacillus thuringiensis
Cite
Citations (42)