Short communicationExpression of the Cry10Aa toxin in transgenic tomato confers tolerance to the tomato leafminer (Tuta absoluta)
Introduction
Tomato (Solanum lycopersicum) is one of the main sources of flavonoids, vitamin C, K1, B2 and B9, potassium, iron, phosphorous and antioxidants, such as lycopene and other carotenoids, that prevent human diseases; indeed, it is the second most important vegetable crop after potato (Laranjeira et al., 2022). World production is about 186 million tons of fresh fruits, which are produced in approximately 5 million hectares (https://www.fao.org/faostat).
Tomato plants are subject to attack by numerous insects that can cause loss of fruit, leaves and even the death of the plant. Plant herbivory by insect pests is considered the largest cause of losses in tomato crops, representing between 50 and 100% of yield loss in developing countries (Biondi et al., 2018; Han et al., 2019). The tomato leafminer (Tuta absoluta) is among the most important predators frequently found in commercial tomato crops in South America, Europe, North Africa and the Middle East, where it has caused extensive economic damage, with yield loss reaching 100% (www.cabi.org/ISC/tuta). It has been incorporated into the list of grades A2 quarantine pests by the European and Mediterranean Plant Protection Organization (EPPO), which reinforces the adaptive capacity of this pest against the most adverse environmental conditions (Roditakis et al., 2010).
The increase in the occurrence and populations of T. absoluta has boosted the use of synthetic insecticides, which provoke disruption of integrated management systems for other tomato pests, and raises the cost of crop protection (Kandil et al., 2020). Consequently, there is considerable interest in the introduction of leafminer resistance into tomato by classical and molecular breeding.
The expression of pesticidal proteins coding genes in transgenic plants, such as δ-endotoxins from Bacillus thuringiensis, has evolved as an important alternative to chemical insecticides, for which there are increasing numbers of records of resistance and control failure of T. absoluta (https://www.pesticideresistance.org/).
Among these toxins, the Crystal (Cry) protein family is one of the most commonly used, which is active against insects of different orders (for a review see Pardo-López et al., 2013). Some of these Cry-coding genes, such as cry1Ac, cry1Ab and cry2Ab, have been expressed in tomato plants, aiming for resistance to insects, such as Helicoverpa armigera (Koul et al., 2014; Hanur et al., 2018), Spodoptera litura (Koul et al., 2014) and T. absoluta (Selale et al., 2017). The Cry10 toxin was identified in a B. thuringiensis subsp. israelenses strain as being toxic to the coleopteran pest coffee berry borer (Hypothenemus hampei) (Méndez‐López et al., 2003). It has been expressed in genetically modified cotton for resistance to boll weevil (Anthonomus grandis) (Ribeiro et al., 2017). Here we report the generation of transgenic tomato lines engineered to express the cry10Aa gene. We hypothesized that the expression of this gene would interfere in the T. absoluta life cycle, generating tolerant tomato plants.
Section snippets
Vector construction and tomato transformation
The cry10Aa gene expression cassette (Fig. 1) was synthesized at Epoch Inc. (Missouri City, TX, USA). The coding sequence of the cry10Aa gene was made according to GenBank accession number OQ659709. The actin 2 promoter from Arabidopsis thaliana was made according to GenBank accession number LR782544.1 (position 6479,373 to 6480,774), and the nos terminator was made according to GenBank accession number MK439386.1 (position 21,537 to 21,790). The cry10Aa cassette was cloned into pCambia2300
Results
Transgenic tomato plants were obtained for the expression of the cry10Aa gene under control of the actin 2 promoter from A. thaliana. PCR analysis revealed the presence of both cry10Aa and nptII transgenes in three transgenic events, named L2, L10 and L11 (Fig. 1).
All the primary plants were acclimatized and allowed to set seeds after 3 months. Segregation analyses of the T1 generation revealed that both cry10Aa and nptII transgenes co-segregated in a Mendelian fashion. The chi-square test
Discussion
Tomato leafminer (T. absoluta) is among the most important insect pests that impair the production of tomatoes in South America, Europe, North Africa and the Middle East, causing extensive economic damage, with the potential to spread to other regions, as occurred recently (Grant et al., 2019). One of the best ways to manage this pest in the field is to develop genetic resistance or tolerance by both classical and molecular breeding. Some efforts have been made to express transgenes into tomato
Funding
This work was partially supported by CNPq Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil, grant number 307111/2018-0).
CRediT authorship contribution statement
Pedro B.B. Fernandes: Conceptualization, Data curation, Methodology, Formal analysis, Writing – review & editing. Lídia N. Queiroz: Investigation, Writing – review & editing. Miguel Michereff-Filho: Investigation, Methodology, Formal analysis. Natália Faustino Cury: Investigation, Writing – review & editing. Kenny Bonfim: Investigation. Glaucia B. Cabral: Methodology, Writing – review & editing. Francisco J.L. Aragão: Supervision, Conceptualization, Investigation, Formal analysis, Writing –
Declaration of Competing Interest
The authors declared no conflict of interest.
Acknowledgments
We thank Dr. Fátima Grossi de Sá (Embrapa, Brazil) for supplying the antibody against Cry10Aa. P. Fernandes and N. Cury were supported by a fellowship from CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil) and FAPDF Fundação de Apoio à Pesquisa do Distrito Federal, Brazil), respectively.
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