Introgression of a dominant phototropin1 mutant enhances carotenoids and boosts flavour-related volatiles in genome-edited tomato RIN mutants.

The tomato (Solanum lycopersicum) ripening inhibitor (rin) mutation is known to completely repress fruit ripening. The heterozygous (RIN/rin) fruits have extended shelf life, ripen normally, but have inferior taste/flavour. To address this, we used genome editing to generate newer alleles of RIN (rin ^CR ) by targeting the K-domain. Unlike previously reported CRISPR alleles, the rin ^CR alleles displayed delayed onset of ripening, suggesting that the mutated K-domain represses the onset of ripening. The rin ^CR fruits had extended shelf life and accumulated carotenoids at an intermediate level between rin and progenitor line. Besides, the metabolites and hormonal levels in rin ^CR fruits were more akin to rin. To overcome the negative attributes of rin, we crossed the rin ^CR alleles with Nps1, a dominant-negative phototropin1 mutant, which enhances carotenoid levels in tomato fruits. The resulting Nps1/rin ^CR hybrids had extended shelf life and 4.4-7.1-fold higher carotenoid levels than the wild-type parent. The metabolome of Nps1/rin ^CR fruits revealed higher sucrose, malate, and volatiles associated with tomato taste and flavour. Notably, the boosted volatiles in Nps1/rin ^CR were only observed in fruits bearing the homozygous Nps1 mutation. The Nps1 introgression into tomato provides a promising strategy for developing cultivars with extended shelf life, improved taste, and flavour.
(© 2023 The Authors. New Phytologist © 2023 New Phytologist Foundation.)