Conventional breeding may lead to more changes than genetic engineering

Oeiras, 26/02/08

Conventional breeding methods in agriculture may lead to more changes in gene expression than genetic engineering. This is the main conclusion of a paper by researchers from ITQB and INSA (Instituto Nacional de Saúde Ricardo Jorge) appearing this week in the online early edition of the Proceedings of the National Academy of Sciences. The authors of the study, Rita Batista, Nelson Saibo, Tiago Lourenço and Margarida Oliveira, propose that the safety assessment of new plant varieties should be carried out on a case-by-case basis and not restricted to foods obtained by genetic engineering.

The research study evaluated the extent of transcriptome modification occurring during rice improvement in two situations: mutation breeding – a conventionally used technique in agriculture – and gene insertion.  The authors found that regardless of the method, improving a plant variety through the acquisition of a new desired trait caused a stress response and thus lead to changes in the expression of untargeted genes. In fact the number of genes altered was significantly higher (at least 2 fold) in the case of mutation, even if the analysed plants were the 10th progeny generation of the modified plants.

The paper version of this article should appear on the March 4th issue of PNAS.

Microarray analyses reveal that plant mutagenesis may induce more transcriptomic changes than transgene insertion

Rita Batista, Nelson Saibo, Tiago Lourenço, and Maria Margarida Oliveira

Abstract

Controversy regarding genetically modified (GM) plants and their potential impact on human health contrasts with the tacit acceptance of other plants that were also modified, but not considered as GM products (e.g., varieties raised through conventional breeding such as mutagenesis). What is beyond the phenotype of these improved plants? Should mutagenized plants be treated differently from transgenics? We have evaluated the extent of transcriptome modification occurring during rice improvement through transgenesis versus mutation breeding. We used oligonucleotide microarrays to analyze gene expression in four different pools of four types of rice plants and respective controls: (i) a γ-irradiated stable mutant, (ii) the M1 generation of a 100-Gy γ-irradiated plant, (iii) a stable transgenic plant obtained for production of an anticancer antibody, and (iv) the T1 generation of a transgenic plant produced aiming for abiotic stress improvement, and all of the unmodified original genotypes as controls. We found that the improvement of a plant variety through the acquisition of a new desired trait, using either mutagenesis or transgenesis, may cause stress and thus lead to an altered expression of untargeted genes. In all of the cases studied, the observed alteration was more extensive in mutagenized than in transgenic plants. We propose that the safety assessment of improved plant varieties should be carried out on a case-by-case basis and not simply restricted to foods obtained through genetic engineering.

Author's affiliation:

• Rita Batista - INSA Auxiliary Investigator and former ITQB PhD student (29/01/2008)
• Nelson Saibo - ITQB Auxiliary Investigator
• Tiago Lourenço - ITQB PhD student
• Margarida Oliveira - Auxiliary Professor at FCUL and Head of the Plant Genetic Engineering Laboratory at ITQB