In this work has been used a collection of a new genotypes of citrus, obtained by means of a physical mutagenesis program developed in the IVIA to study different phenotypic, molecular and metabolic aspects related with the fruit ripening.
To achieve these aims, genotypes of Clementina with alterations in the ripening of their fruits were selected and characterized and genes involved in internal ripening of the citrus fruit were functional characterized. On the other hand, deletion genes were detected in Clementine’s mutants and finally the degradation of citric acid process in the fruits was studied, doing special upsetting in the function of the phosphoenolpyruvate carboxykinase gene.
Like this, microarrays of cDNA specific of citrus generated by the Consortiun of Citrus Genome have been employed to study the simultaneous expression of 20.000 genes in several states of ripening fruit in the genotypes selected. The bioinformatic analysis allowed to identify 161 genes correlated with the fruit ripening process. Moreover, it was found a significant correlation between the acidity and some of these genes, which expression was confirmed by means of real-time RT-PCR. Like this, was checked that the PEPCK expression increased along the fruit ripening. The numer of genes in citrus belong to the family of PEPCK was determined just as its specificity in different commercial varieties. During the Clementine’s fruit ripening, the initial induction of PEPCK was happened during the fast acidity reduction phase and the increase of  sugars.  An experiment with supplement of citric acid suggested that the carbon flux come from the acids degradation by the GABA route is employed in the gluconeogenesis to sugar synthesis, being the activation of PEPCK the connector element of both processes.