The 3-ketoacyl-CoA synthase WFL is involved in lateral organ development and cuticular wax synthesis inMedicago truncatula

Key message A 3-ketoacyl-CoA synthase involved in biosynthesis of very long chain fatty acids and cuticular wax plays a vital role in aerial organ development inM. truncatula. Cuticular wax is composed of very long chain fatty acids and their derivatives. Defects in cuticular wax often result in organ fusion, but little is known about the role of cuticular wax in compound leaf and flower development inMedicago truncatula. In this study, through an extensive screen of aTnt1retrotransposon insertion population inM. truncatula, we identified four mutant lines, namedwrinkled flower and leaf(wfl) for their phenotype. The phenotype of thewflmutants is caused by aTnt1insertion inMedtr3g105550, encoding 3-ketoacyl-CoA synthase (KCS), which functions as a rate-limiting enzyme in very long chain fatty acid elongation. Reverse transcription-quantitative PCR showed thatWFLwas broadly expressed in aerial organs of the wild type, such as leaves, floral organs, and the shoot apical meristem, but was expressed at lower levels in roots. In situ hybridization showed a similar expression pattern, mainly detecting theWFLtranscript in epidermal cells of the shoot apical meristem, leaf primordia, and floral organs. Thewflmutant leaves showed sparser epicuticular wax crystals on the surface and increased water permeability compared with wild type. Further analysis showed that inwflleaves, the percentage of C20:0, C22:0, and C24:0 fatty acids was significantly increased, the amount of cuticular wax was markedly reduced, and wax constituents were altered compared to the wild type. The reduced formation of cuticular wax and wax composition changes on the leaf surface might lead to the developmental defects observed in thewflmutants. These findings suggest that WFL plays a key role in cuticular wax formation and in the late stage of leaf and flower development inM. truncatula.

Automated summary

This study revealed the crucial role of a 3-ketoacyl-CoA synthase (KCS) enzyme involved in the biosynthesis of very long chain fatty acids and cuticular wax in the aerial organ development of Medicago truncatula. Mutants with defects in cuticular wax showed altered leaf surface wax composition and developmental defects.