NAC-NOR mutations in tomato Penjar accessions attenuate multiple metabolic processes and prolong the fruit shelf life

Abstract

Several Penjar accessions of tomato (Solanum lycopersicum), widely grown in the Mediterranean region, exhibit prolonged shelf life, and harbor alcobaca mutation with valine-106-aspartic acid substitution in the NAC-NOR protein. To uncover the metabolic basis underlying the prolonged shelf life, we compared four Penjar accessions to Ailsa Craig (AC). Three accessions bore alcobaca mutation, whereas fourth was a novel NAC-NOR allele with only six amino acids in the encoded protein. The cuticle composition among Penjars varied widely during the progression of fruit ripening. All Penjars exhibited delayed ripening, prolonged on-vine and off-vine shelf life, low ethylene emission and carotenoid levels albeit with accession-specific differences. Metabolic profiling revealed shifts in Krebs cycle intermediates, amino acids, and {beta}-aminobutyric acid levels indicating the attenuation of respiration in Penjars during post-harvest storage. The prolonged shelf life of Penjar fruits was associated with a concerted downregulation of a number of cell-wall modifying genes and cell-wall-related metabolites. The accumulation of higher ABA and sucrose levels at the onset of senescence in Penjar fruits likely contribute to reduced water loss. Our analyses reveal that in addition to specialized cuticle composition, the attenuation of various metabolic processes by NAC-NOR mutation likely prolongs the shelf life of Penjar fruits.\n\nHighlightThe prolonged shelf life of tomato Penjar accessions bearing mutations in NAC-NOR transcription factor appears to be regulated by a combined effect of attenuation of respiration, altered cuticle composition, enhanced ABA and sucrose levels in fruits and downregulation of cell wall modification