Abstract
The interface between plants and the environment is provided for aerial organs by epicuticular waxes that have been extensively studied. By contrast, little is known about the nature, biosynthesis, and role of waxes at the root-rhizosphere interface. Waxes isolated by rapid immersion of Arabidopsis (Arabidopsis thaliana) roots in organic solvents were rich in saturated C18-C22 alkyl esters of p-hydroxycinnamic acids, but also contained significant amounts of both alpha- and beta-isomers of monoacylglycerols with C22 and C24 saturated acyl groups and the corresponding free fatty acids. Production of these compounds in root waxes was positively correlated to the expression of sn-glycerol-3-P acyltransferase5 (GPAT5), a gene encoding an acyltransferase previously shown to be involved in aliphatic suberin synthesis. This suggests a direct metabolic relationship between suberin and some root waxes. Furthermore, when ectopically expressed in Arabidopsis, GPAT5 produced very-long-chain saturated monoacylglycerols and free fatty acids as novel components of cuticular waxes. The crystal morphology of stem waxes was altered and the load of total stem wax compounds was doubled, although the major components typical of the waxes found on wild-type plants decreased. These results strongly suggest that GPAT5 functions in vivo as an acyltransferase to a glycerol-containing acceptor and has access to the same pool of acyl intermediates and/or may be targeted to the same membrane domain as that of wax synthesis in aerial organs.
Highlights
The interface between plants and the environment is provided for aerial organs by epicuticular waxes that have been extensively studied
We show that ectopic expression of glycerol-3-P acyltransferase5 (GPAT5) under the control of the cauliflower mosaic virus (CaMV) 35S promoter leads to production of a- and b-isomers of MAGs as novel components of leaf and stem surface waxes, changing significantly the composition and morphology of the aerial cuticle
We found that a 10-s dip in chloroform, sufficient to recover .98% (w/w) of total surface waxes from Arabidopsis stems, extracted significant amounts of lipid material from roots (Fig. 2, A and B)
Summary
The interface between plants and the environment is provided for aerial organs by epicuticular waxes that have been extensively studied. Waxes isolated by rapid immersion of Arabidopsis (Arabidopsis thaliana) roots in organic solvents were rich in saturated C18C22 alkyl esters of p-hydroxycinnamic acids, and contained significant amounts of both a- and b-isomers of monoacylglycerols with C22 and C24 saturated acyl groups and the corresponding free fatty acids Production of these compounds in root waxes was positively correlated to the expression of sn-glycerol-3-P acyltransferase (GPAT5), a gene encoding an acyltransferase previously shown to be involved in aliphatic suberin synthesis. The crystal morphology of stem waxes was altered and the load of total stem wax compounds was doubled, the major components typical of the waxes found on wild-type plants decreased These results strongly suggest that GPAT5 functions in vivo as an acyltransferase to a glycerol-containing acceptor and has access to the same pool of acyl intermediates and/or may be targeted to the same membrane domain as that of wax synthesis in aerial organs. We show that ectopic expression of GPAT5 under the control of the cauliflower mosaic virus (CaMV) 35S promoter leads to production of a- and b-isomers of MAGs as novel components of leaf and stem surface waxes, changing significantly the composition and morphology of the aerial cuticle
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