3-ketoacyl-CoA synthases (KCSs), as components of a fatty acid elongase (FAE) complex, play key roles in determining the chain length of very-long-chain fatty acids (VLCFAs).
KCS6, taking a predominate role during the elongation from C26 to C28, is well known to play an
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3-ketoacyl-CoA synthases (KCSs), as components of a fatty acid elongase (FAE) complex, play key roles in determining the chain length of very-long-chain fatty acids (VLCFAs).
KCS6, taking a predominate role during the elongation from C26 to C28, is well known to play an important role in wax synthesis.
KCS5 is one paralog of
KCS6 and its role in wax synthesis remains unknown. Wax phenotype analysis showed that in
kcs5 mutants, the total amounts of wax components derived from carbon 32 (C32) and C34 were apparently decreased in leaves, and those of C26 to C32 derivatives were obviously decreased in flowers. Heterologous yeast expression analysis showed that
KCS5 alone displayed specificity towards C24 to C28 acids, and its coordination with
CER2 and
CER26 catalyzed the elongation of acids exceeding C28, especially displaying higher activity towards C28 acids than
KCS6. BiLC experiments identified that
KCS5 physically interacts with
CER2 and
CER26. Wax phenotype analysis of different organs in
kcs5 and
kcs6 single or double mutants showed that
KCS6 mutation causes greater effects on the wax synthesis than
KCS5 mutation in the tested organs, and simultaneous repression of both protein activities caused additive effects, suggesting that during the wax biosynthesis process,
KCS5 and
KCS6 play redundant roles, among which
KCS6 plays a major role. In addition, simultaneous mutations of two genes nearly block drought-induced wax production, indicating that the reactions catalyzed by
KCS5 and
KCS6 play a critical role in the wax biosynthesis in response to drought.
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