KCS1encodes a fatty acid elongase 3‐ketoacyl‐CoA synthase affecting wax biosynthesis inArabidopsis thaliana

Abstract

SummaryAn Arabidopsis fatty acid elongase gene, KCS1, with a high degree of sequence identity to FAE1, encodes a 3-ketoacyl-CoA synthase which is involved in very long chain fatty acid synthesis in vegetative tissues, and which also plays a role in wax biosynthesis. Sequence analysis of KCS1 predicted that this synthase was anchored to a membrane by two adjacent N-terminal, membrane-spanning domains. Analysis of a T-DNA tagged kcs1-1 mutant demonstrated the involvement of the KCS1 in wax biosynthesis. Phenotypic changes in the kcs1-1 mutant included thinner stems and less resistance to low humidity stress at a young age. Complete loss of KCS1 expression resulted in decreases of up to 80% in the levels of C26 to C30 wax alcohols and aldehydes, but much smaller effects were observed on the major wax components, i.e. the C29 alkanes and C29 ketones on leaves, stems and siliques. In no case did the loss of KCS1 expression result in complete loss of any individual wax component or significantly decrease the total wax load. This indicated that there was redundancy in the elongase KCS activities involved in wax synthesis. Furthermore, since alcohol, aldehyde, alkane and ketone levels were affected to varying degrees, involvement of the KCS1 synthase in both the decarbonylation and acyl-reduction wax synthesis pathways was demonstrated.

Wax Layers onCosmos bipinnatusPetals Contribute Unequally to Total Petal Water Resistance

“…Phaseolus vulgaris (Steinmüller and Tevini, 1985), Medicago truncatula (Zhang et al, 2005), and Pisum sativum (Gniwotta et al, 2005; the composition of V. faba leaf wax has not been reported yet). Arabidopsis flower wax is dominated by C 29 alkane (Shi et al, 2011), shorter than the prevalent C 31 homolog in leaves (Jenks et al, 1995) but similar to inflorescence stems and siliques (Todd et al, 1999). Overall, there appears to be a fairly widespread compositional pattern in flower waxes, in many species characterized by the presence of shorter chain lengths than on vegetative organs.…”

Salt Induction of Fatty Acid Elongase and Membrane Lipid Modifications in the Extreme Halotolerant Alga Dunaliella salina

“…Nonetheless, as shown below, the first 46 N-terminal residues are not essential for enzymatic activity. Another difference noted is that only four of the six Cys residues conserved in other Kcs proteins (Todd et al, 1999) are present in the algal Kcs. Recently reported mutagenesis experiments indicated that only a single Cys residue (residue 223 in the Arabidopsis FAE1) was essential for activity (Ghanevati and Jaworski, 2001).…”

“…Additional plant genes belonging to this family were identified on the basis of sequence homology or as transposon insertion sites in tagged mutants (Fourman et al, 1998;Millar et al, 1998;Yephremov et al, 1999;Priutt et al, 2000). Functionally characterized plant kcs genes include genes expressed in seeds and active in the biosynthesis of storage lipids or waxes (Lassner et al, 1996), as well as genes expressed in vegetative tissues and involved in the biosynthesis of cuticular waxes (Millar et al, 1999;Todd et al, 1999). The D. salina Kcs, identified in the context of algal salt responses, is most likely involved in membrane lipid biosynthesis.…”

Disruption of Glycosylphosphatidylinositol-Anchored Lipid Transfer Protein Gene Altered Cuticular Lipid Composition, Increased Plastoglobules, and Enhanced Susceptibility to Infection by the Fungal Pathogen Alternaria brassicicola

“…During this process, the C16 and C18 fatty acids synthesized in the plastids are exported to the cytosol, where they are further elongated to VLCFAs in the range of 20 to 34 carbons by the fatty acid elongase complex on the endoplasmic reticulum (ER; Millar and Kunst, 1997;Millar et al, 1999;Todd et al, 1999;Yephremov et al, 1999;Fiebig et al, 2000;Clemens and Kunst, 2001;Hooker et al, 2002;Dietrich et al, 2005;Zheng et al, 2005). The elongated VLCFAs are then further transformed by two principal wax biosynthetic pathways: an acyl reduction pathway that produces primary alcohols and wax esters, and a decarbonylation pathway that leads to the formation of aldehydes, alkanes, secondary alcohols, and ketones (Aarts et al, 1995;Kunst and Samuels, 2003;Rowland et al, 2006).…”