Tomato vs Grape

Tomato and grape are currently the best models for deciphering the common and specific regulatory processes and mechanisms controlling fruit growth and ripening in climacteric and non-climacteric fleshy fruits. Both are berries and emerge as models for exploring the major regulation mechanisms involved in the coordination of fleshy fruit development. Tomato is already considered as the main model species for fleshy fruit development while grape attracts an increasing number of scientists due to its strong economical importance and to the recent development of advanced genomics tools in this species. As a result, tools for exploring fruit development at the genomic level are largely available for both species; some of them have been generated only recently. In order to explore the commonalities and specific strategies developed by fleshy fruit species, this COST Action will initiate a comparative genomic analysis at the transcriptome and metabolome levels to unravel the molecular features underlying fruit development from two unrelated species of great agronomical importance belonging to distant families: the tomato (Solanaceae) as climacteric and the grape (Vitaceae) as non-climacteric.

From the social aspects, fruits such as tomatoes and grapes are recommended as part of a healthy diet because they are rich sources of micronutrients and fiber. Although consumers are aware of these benefits, they are nevertheless more likely to choose fruits with the most appealing sensory characteristics (flavor, texture, aroma and color). Therefore, efficient promotion of daily fruit consumption cannot only rely on the improvement of their nutritional value, but also requires rendering fruits more attractive to the consumer at the sensory level. A better understanding of fruit biology is hence needed to facilitate the improvement of both nutritional and sensory characteristics.

Tomato and grape share some commonalities with other fleshy fruits but display specific developmental and metabolic regulatory mechanisms. The grape berries development follows a double sigmoid pattern of growth and the regulation of this process remains unclear though like in many fleshy fruit species, the influence of hormones, possibly released by the seeds, may play a considerable role in the control of the developmental changes. In tomato and several other fleshy fruit species, final fruit size is also determined by the endoreduplication process which leads to higher ploidy level and increased size of the nucleus resulting from DNA duplication in the absence of mitosis. In grape, cell expansion period is much longer but is independent from endoreduplication. Pathways and physiological processes that are crucial for fruit quality display some commonalities but also differences between the two fruit species. Shared metabolic aspects include sugar which accumulates throughout ripening in grape as soluble sugars while it accumulates transiently as starch in tomato. Malic and tartric acid are the main organic acids in grape while in tomato accumulate malic and citric acids.

On the other hand phenylpropanoid metabolites are of primary importance in processed grapes but are of minor importance in tomato.