Plant waxes
complex mixtures H/C, alcohols, aldehydes, ketones, esters, acids, etc.
epidermal - synthesis occurs there and waxes are exuded onto the surface
cutin - crosslinked hydroxyacids impregnated with other components
suberin - on roots, more aromatic residues incorporated
Biosynthesis
stearyl-CoA ----> NADPH, malonyl-CoA ----> C28, C30, and C32
not stearyl-ACP
-CO2H ----> fatty acyl-CoA reductase -----> CH2OH
-CO2H ----> NADH -----> CHO
-CO2H + -CH2OH ---> acyl-CoA alcohol transacylase ---->
CO-O-CH2-
wax esters
Simmondsia chinensis, jojoba, contains C20 and C22-based liquid wax esters.
when acetate was fed into this plant, it mostly was incorporated into chain extension
Alkanes
C12, C14, C16, C18 FA's ----> C29 H/Cs
"compounds that are efficient precursors for acids are efficient precursors for H/C's"
C30 FA ----> O2 ----> C29 H/C (in Brassica oleracea) an α-hydroxy intermediate is involved
Importance of waxes
surface - offers protection against attack, dehydration, etc.
surface waxes are important in contact chemoreception. Insects are also important
Cutin and suberin
cutin - C18 and C16-monomers - depends on the plant
16-hydroxypalmitic acid and 10,16-dihydroxypalmitic acid and others
suberin - mostly ω-hydroxy acids
common phenolic components are p-coumaric acid, ferulic acid etc.
© David S. Seigler, Integrative Biology 425, Plant Secondary Metabolism, Department of Plant
Biology, 265 Morrill Hall, 505 S. Goodwin Ave., University of Illinois, Urbana, Illinois 61801, USA.
217-333-7577. seigler@life.uiuc.edu.