OsKCS11 Links Very-Long-Chain Fatty Acids and Cytokinin in Rice Dwarfism

Research on very-long-chain fatty acids (VLCFAs) in plants, critical for various physiological processes, led to the identification of a semi-dwarf rice mutant, CRISPR-Cas-based dwarf-1 (csd-1), through a CRISPR-Cas9 knockout library. This mutant exhibited a range of developmental defects, including reduced plant height, panicle length, seed size, and seed-setting rate. Whole-genome resequencing pinpointed a T-nucleotide insertion in the β-ketoacyl-CoA synthase 11 (KCS11) gene as the cause. KCS11 is crucial for the initial step of fatty acid elongation, and its role was confirmed through genetic complementation and further CRISPR-Cas9 knockout. Expression analysis showed OsKCS11 presence across various tissues, with strong localization at nodes, and its protein was found in the endoplasmic reticulum.

Further analysis of csd-1 revealed significant alterations in fatty acid profiles, with reduced levels of linolenic acid (18:3), C24:0-OH, C28:0-alkanes, C29:0-alkanes, alpha-tocopherol, and C33:0-alkanes, while trans-nonadecenoic acid and behenic acid levels increased. Importantly, cytokinin analysis showed elevated levels of isopentenyladenine (IPA) and cis-zeatin (cZ) in csd-1.

Molecular investigations indicated an upregulation of genes related to cytokinin biosynthesis or signaling, suggesting a novel connection between VLCFAs and cytokinin synthesis, potentially mediated by acetyl-CoA. The study not only presented a new gene mapping method using whole-genome resequencing but also shed light on the intricate mechanism by which VLCFAs influence cytokinin synthesis and signaling pathways in plants.

Read more from The Plant Journal.