Identification of Polyketides in the Cuticular Waxes of Triticum aestivum cv. Bethlehem

Abstract

Cuticular waxes are complex mixtures consisting mostly of very-long-chain aliphatics with single, primary functional groups. However, the waxes of many plant species also include aliphatics with one or more functional groups residing on subterminal or mid-chain carbons. In the present work, the cuticular wax mixtures from flag leaf blades and peduncles of Triticum aestivum cv. Bethlehem were analyzed in a search for novel wax constituents with in-chain functionalities, potentially of polyketide origin. The structures of compounds belonging to six different compound classes were elucidated using gas chromatography-mass spectrometry of various derivatives. Among them, a series of 2,4-ketols was identified, with odd carbon numbers ranging from C to C and peaking at C. The analogous C 2,4-diketone was identified as well, together with a pair of co-eluting C mid-chain β-ketol isomers (16-hydroxyhentriacontan-14-one and 14-hydroxyhentriacontan-16-one), a pair of co-eluting C mid-chain α-ketol isomers (15-hydroxytriacontan-14-one and 14-hydroxytriacontan-15-one), the corresponding C 14,15-diketone, and a pair of co-eluting C ketones (hentriacontan-14-one and hentriacontan-16-one). All newly discovered structures contain ketone functional groups, with similar CH and CH alkyl chains on either side of the functionalities, thus resembling the previously reported very-long-chain β-diketones dominating the wheat wax mixtures. Based on these structural characteristics, possible biosynthetic pathways leading to the newly identified polyketide-like compounds are proposed.

Husk to caryopsis adhesion in barley is influenced by pre- and post-anthesis temperatures through changes in a cuticular cementing layer on the caryopsis

“…In Additional file 2 diagnostic ions seen in the mass spectra are marked with an asterisk and those used for quantification are underlined. Mass spectral fragmentation schemes for the different enol and (enol) 2 tautomers of hentriacontan-14, 16-dione are dominated by ions arising from fragmentation α or ß to the carbonyl or OTMS groups, with fragments incorporating OTMS being favoured [ 51 ]. The mass spectra of the four enols appear to be very similar and it was not possible to distinguish between them on the basis of their mass spectra since the same ion groups were used for identification and quantification.…”

Smart water channelling through dual wettability by leaves of the bamboo Phyllostachys aurea

“…An identical age-related chain length effect was observed for amides, also peaking at C30 and with shorter homologs more abundant for young and longer ones for old plant leaves. Further evidence for amide structure elucidation and related biology will be presented elsewhere 30 . Finally, the ester homolog profiles peaked at C48 on leaf surfaces of both ages, accompanied by near-identical amounts of the C46, C44, and C42 homologs, and higher proportions of C40 and C38 homologs on young leaves versus higher abundance of the C50 homolog on old leaves.…”

TaCER1‐1A is involved in cuticular wax alkane biosynthesis in hexaploid wheat and responds to plant abiotic stresses

“…For example, many cereal crop species have high concentrations of β‐diketones in their waxes (von Wettstein‐Knowles, ). In this context, wheat waxes have been investigated in much chemical detail, revealing substantial variation between different cultivars, organs, and growth stages (Racovita et al, ; Racovita & Jetter, ; Racovita & Jetter, ). Further research suggested that wax alkanes accumulated mostly in the heading and later stages of wheat development, in particular on flag leaf blades, peduncles, and spikes (Wang et al, ; Wang et al, ).…”