Reciprocal effect and heterosis for tomato fruit metabolites revealed by whole transcriptomic analysis of two cultivars and their reciprocal hybrids

Abstract

External and internal attributes of fleshy fruits can be affected by phenomena like reciprocal effect and heterosis. The aim of this work is to study the genetic and molecular differences between two parental lines and their reciprocal hybrids, as well as the presence of heterosis and reciprocal effects. The tomato cultivars Querubín FCA and Gema FCA were selected as parental genotypes because this cross showed a high presence of heterosis and reciprocal effect. A combined investigation of the gene actions involved in gene expression profile and metabolic content was performed by analysing transcriptomic data and its integration with previously reported metabolic data. The reciprocal hybrids showed the most significant differences at the transcript levels (157 out of 200). Several transcripts which encode transcription factors were found, suggesting that ripe red fruits still have a highly regulated transcriptome. Furthermore, 41 differentially expressed genes connected to 11 metabolites were identified. Afterwards, transcript and metabolite gene actions were calculated. The results showed that the metabolic phenotypes of the parental genotypes are mainly explained by transcripts showing an additive gene action. In contrast, transcripts with non-additive gene actions mainly explained the heterotic metabolic phenotype in the hybrids. This work contributes to a deeper understanding of the molecular basis of reciprocal effect and heterosis in plant crops.