Isochorismate synthase is required for phylloquinone, but not salicylic acid biosynthesis in rice.

Unlabelled: Salicylic acid (SA) is a phytohormone required for plant growth and defense signaling. There are two major SA biosynthesis pathways in plants: the isochorismate synthase (ICS) pathway and the phenylalanine ammonia-lyase (PAL) pathway. It has been demonstrated in several plant species, including the model plant , that SA is derived predominantly from the ICS pathway. Here, we employed the CRISPR/Cas9 system to generate knockout mutants in rice ( L.). The mutants display severe growth defects, and are completely devoid of phylloquinone, an isochorismate-derived product. The growth defects of can be rescued through exogenous application of 1,4-dihydroxy-2-naphthoic acid (NA), a precursor of phylloquinone. Remarkably, the basal SA levels are not altered in the mutants. Our findings support a role of OsICS in the biosynthesis of phylloquinone, and imply that SA biosynthesis in rice may occur through an alternative route other than the ICS pathway.

Supplementary Information: The online version contains supplementary material available at 10.1007/s42994-024-00166-4.