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Scientists develop transgenic tomatoes with increased resistance to the common cutworm

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March, 2008

Source: CropBiotech Update

Scientists from the Suranaree University of Technology in Thailand and Louisiana State University have developed transgenic tomato lines with increased resistance to the common cutworm. The transgenic lines were modified to express a potato gene coding for the enzyme polyphenol oxidase (PPO). Polyphenol oxidase, which has also been implicated for plant resistance to the bacterium Pseudomonas syringae catalyzes the conversion of phenolics to quinones, plant secondary metabolites that are involved in pathogen defense.

Growth rates of cutworm in the PPO-expressing lines were up to three times lower compared to their non-transgenic counterparts. Higher levels of PPO also resulted to increased larval mortality, with the cutworm third instar consuming less foliage. The results suggest a critical role for PPO-mediated phenolic oxidation in pest resistance.

Article published by the Plant Journal at http://dx.doi.org/10.1016/j.plantsci.2008.01.006

Source: Plant Science
Volume 174, Issue 4, April 2008, Pages 456-466

Overexpression of tomato polyphenol oxidase increases resistance to common cutworm
Siraprapa Mahanil(a), Jutharat Attajarusit(a), Michael J.Stout(b) and Piyada Thipyapong(a)
(a)School of Crop Production Technology, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
(b)Department of Entomology, 402 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803, USA
Received 23 May 2007; revised 7 January 2008; accepted 11 January 2008. Available online 21 January 2008.

ABSTRACT

Polyphenol oxidases (PPOs), which catalyze the oxidation of phenolics to quinones, have been reported to confer resistance to Pseudomonas syringae and are thought to be involved in insect resistance. To assess the impact of PPO expression on resistance to the common cutworm (Spodoptera litura (F.)) (Lepidoptera: Noctuidae), we used transgenic tomato (Lycopersicon esculentum Mill.) plants constitutively expressing sense- and antisense-oriented potato PPO genes. Transgenic plants expressing a sense PPO construct (overexpressing PPO [OP] plants) exhibited 2.0–5.7-fold higher PPO activity levels, whereas antisense PPO transgenic plants (suppressed PPO [SP] plants) exhibited 1.5–7.3-fold lower PPO activity levels than nontransformed controls. The PPO-overexpressing transgenic plants clearly showed an increase in resistance; simple growth rates of common cutworms on OP plants were up to 2.5 and 3.3 times lower than on controls and SP leaves, respectively, and larvae consumed less foliage. In addition, increased PPO activity led to higher larval mortality. The efficiency of conversion of ingested food and efficiency of conversion of digested food of third instars were found to be significantly different among tomato genotypes with differing PPO activity levels, suggesting that PPO activity rendered foliage less nutritious. Moreover, when leaflets at nodes 4 and 8 of SP, NT and OP plants were detached and fed to common cutworm larvae, their PPO activity levels were induced 1.6–2.2-fold. These results suggest a critical role for PPO-mediated phenolic oxidation in resistance to this insect. Manipulation of PPO activity could provide resistance simultaneously to both disease and insect pests, and therefore might be used as a component of effective integrated pest management.

 

 

 

 

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