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© 2020 by the authors., San Marzano (SM) is a traditional Italian landrace characterized by red elongated fruits, originating in the province of Naples (Italy) and cultivated worldwide. Three mutations, yellow flesh (r), green flesh (gf) and colorless fruit epidermis (y) were introduced into SM by backcross and the resulting introgression lines (ILs) produced the expected yellow, brown and pink fruit variants. In addition, ILs carrying double combinations of those mutations were obtained. The six ILs plus the SM reference were analyzed for volatile (VOC), non-polar (NP) and polar (P) metabolites. Sixty-eight VOCs were identified, and several differences evidenced in the ILs; overall gf showed epistasis over r and y and r over y. Analysis of the NP component identified 54 metabolites; variation in early carotenoids (up to lycopene) and chlorophylls characterized respectively the ILs containing r and gf. In addition, compounds belonging to the quinone and xanthophyll classes were present in genotypes carrying the r mutation at levels higher than SM. Finally, the analysis of 129 P metabolites evidenced different levels of vitamins, amino acids, lipids and phenylpropanoids in the ILs. A correlation network approach was used to investigate metabolite–metabolite relationships in the mutant lines. Altogether these differences potentially modified the hedonistic and nutritional value of the berry. In summary, single and combined mutations in gf, r and y generated interesting visual and compositional diversity in the SM landrace, while maintaining its original typology., This work was supported by the European Commission through-H2020 SFS-7a-2014 TRADITOM (634561) and the COST Actions ROXy CA18210 and EUcarotene CA15136 for networking. The Italian Ministry for Education, University and Research (MIUR) Law 232/216, Department of Excellence and the Spanish Ministry project BIO2016-78601-R are also acknowledged.

Black- and white-berried grapevine cultivars are distinguished by their ability to accumulate anthocyanins in the berry skin. To assess possible side effects of color variation in berry development and composition in a near-isogenic background, we compared white-berried somatic variants (WV) to their black-berried ancestors in ‘Garnacha’ and ‘Tempranillo’ cultivars. Absence of anthocyanins correlated with lower berry temperature during daytime in WV. At the transcriptome level, besides genes related to anthocyanin accumulation, transcripts encoding enzymes involved in flavonoid backbone biosynthesis and modification were downregulated from veraison in WV skin. Genes mapping to hemizygous genome regions in WV were also downregulated irrespective of berry tissue or developmental stage. Light-responsive genes including flavonol and monoterpenoid biosynthesis genes were upregulated in WV from veraison. In agreement, flavonol partitioning was altered and tri-hydroxylated forms were practically absent in WV, whereas higher levels of specific volatile monoterpenoids and their soluble precursors were detected in WV pericarp. Amino acid precursors of phenolic compounds tended to be higher in WV pericarp. Collectively, greater differences were observed in ‘Tempranillo’ than in ‘Garnacha’, revealing effects of genetic background. These results indicate that the grape color locus directly controls the metabolism of colorless flavonoids, whereas additional alterations in grape quality compounds are established in a cultivar-dependent manner in response to alteration of the berry microclimate caused by the absence of anthocyanins.

Polyamine oxidases (PAOs) are flavin-dependent enzymes involved in polyamine catabolism. In Arabidopsis five PAO genes (AtPAO1-AtPAO5) have been identified which present some common characteristics, but also important differences in primary structure, substrate specificity, subcellular localization, and tissue-specific expression pattern, differences which may suggest distinct physiological roles. In the present work, AtPAO5, the only so far uncharacterized AtPAO which is specifically expressed in the vascular system, was partially purified from 35S::AtPAO5-6His Arabidopsis transgenic plants and biochemically characterized. Data presented here allow AtPAO5 to be classified as a spermine dehydrogenase. It is also shown that AtPAO5 oxidizes the polyamines spermine, thermospermine, and N1-acetylspermine, the latter being the best in vitro substrate of the recombinant enzyme. AtPAO5 also oxidizes these polyamines in vivo, as was evidenced by analysis of polyamine levels in the 35S::AtPAO5-6His Arabidopsis transgenic plants, as well as in a loss-of-function atpao5 mutant. Furthermore, subcellular localization studies indicate that AtPAO5 is a cytosolic protein undergoing proteasomal control. Positive regulation of AtPAO5 expression by polyamines at the transcriptional and post-transcriptional level is also shown. These data provide new insights into the catalytic properties of the PAO gene family and the complex regulatory network controlling polyamine metabolism. © The Author 2014.