Alteration of TCA in transgenic tomato plants shows a crucial role of organic acids in crop development and fruit quality

Abstract

Tomato (Solanum lycopersicum) is second most consumed vegetable in the world, but also a model plant for the study of fleshy fruit ripening and senescence owing to its genetic and molecular tractability. Organic acids play a crucial role in the plant primary metabolism (Araújo et al., 2012) and are considered as being ones of the most important fruit quality traits (Oms-Oliu et al., 2011). Transgenic tomato (Solanum lycopersicum) plants expressing constitutively a bacterial maleate isomerase, which converts maleate to fumarate, were generated in order to improve our knowledge about the role of organic acids in the crop and fruit metabolism. Growth and reproduction were affected by the unbalance organic acids, as a dwarf phenotype and a flowering delay were observed in the transgenic plants. In addition, a lower level in chlorophyll content, a decrease in the numbers of stomata indicated alterations in photosynthesis. Postharvest was also impaired, as transgenic fruits showed increased water loss and deterioration, indicating a possible role of the organic acids in the cell wall metabolism, confirm by changes in the expression of some genes involve in. Finally, metabolomics analysis pointed out important changes during fruit ripening in primary metabolites metabolites, such as organic acids, amino acids, and sugars, revealing the importance of organic acids in fruit metabolism. These data indicate a pivotal role of tricarboxylic cycle intermediates, such as malate or fumarate, as regulatory metabolites. Besides their roles in quality fruit characteristics, they are involved in different functions including growth and photosynthesis.