Pink tomatoes developed with CRISPR-Cas9

One of the most important traits of tomatoes, commercially speaking, is their colour. Consumers have different colour preferences depending on the region where they are located. For example, European and US consumers prefer red tomatoes, while pink tomatoes are more popular in Asian countries, particularly in China and Japan.

However, most tomato growing materials are red fruits, so the development of materials with pink fruits is very important for the production of Asian tomatoes. Metabolic and genetic studies show that the pink trait is the result of the absence of flavonoid yellow naringenin chalcone (NarCh) in the outer layer, and this is controlled by the recessive monogenic yellow locus (Y). More and more evidence suggests that the Y gene can encode a transcription factor R2R3-MYB, SlMYB12, which acts as a key determinant for the accumulation of flavonoids.

The silencing of the SlMYB12 gene in plants with pink fruits blocks the accumulation of NarCh in the outer layer and results in a pink fruit phenotype. Also, the overexpression of the gene leads to phenotypic complementation. All this suggests that the genetic manipulation of SlMYB12 is a feasible way to change the colour of the fruit and choose between red and pink. Lei Deng's team, from the Chinese Academy of Sciences, is working on the development of pink tomatoes by targeting the SlMYB12 gene.

The researchers used CRISPR-Cas9 to alter this gene in red fruit tomato lines. 11 individual regeneration plants were developed, 10 of which had at least one mutated SlMYB12 allele, which revealed high editing efficiency (90.9%). All homozygous and biallelic mutants had a pink fruit phenotype.