RNA silencing is a mechanism used by plants to defend themselves from pathogens. In tomato, the DCL family is responsible for the production of small RNAs (sRNAs), which are molecules needed in the recognition of foreign, viral nucleic acids for silencing. Out of four DCL proteins, DCL2 is the least studied. Therefore, to further know the function of the DCL2 protein in tomato, the second most consumed vegetable in the world, researcher Hongliang Zhu from China Agricultural University and colleagues use CRISPR-Cas9 to knockout and know the function of DCL2.

The researchers mutate DCL2b and find 5 bp homozygous deletions that caused a premature stop codon in the mutants. The mutants have normal developmental morphology, but show severe defects in the leaves, flowers, and fruits when infected with Tomato Mosaic Virus (ToMV). This result indicates the major role of DCL2b in the plant's defense against ToMV. Further analyses show the role of the protein in the biogenesis of 22-nt miRNAs. Overall, these results provide new insights in tomato viral defense.

For more information, read the article in Horticulture Research.