Genetic and biochemical evidence for involvement of HOTHEAD in the biosynthesis of long-chain alpha-,omega-dicarboxylic fatty acids and formation of extracellular matrix.
In plants, extracellular matrix polymers built from polysaccharides and cuticular lipids have structural and protective functions. The cuticle is found to be ten times thinner in Arabidopsis thaliana (L.) Heynh than in many other plants, and there is evidence that it is unusual in having a high content of alpha-,omega-dicarboxylic fatty acids (FAs) in its polyesters. We designated the new organ fusion mutant hth-12 after it appeared to be allelic to adhesion of calyx edges (ace) and hothead (hth), upon molecular cloning of the gene by transposon tagging. This mutant is deficient in its ability to oxidize long-chain omega-hydroxy FAs to omega-oxo FAs, which results in leaf polyesters in decreased alpha-,omega-dicarboxylic FAs and increased omega-hydroxy FAs. These chemical phenotypes lead to disorder of the cuticle membrane structure in hth-12. ACE/HTH is a single-domain protein showing sequence similarity to long-chain FA omega-alcohol dehydrogenases from Candida species, and we hypothesize that it may catalyze the next step after cytochrome P450 FA omega-hydroxylases in the omega-oxidation pathway. We show that ACE/HTH is specifically expressed in epidermal cells. It appears very likely therefore that the changes in the amount of alpha-,omega-dicarboxylic FAs in hth-12 reflect the different composition of cuticular polyesters. The ACE/HTH gene is also expressed in root epidermal cells which do not form a polyester membrane on the exterior surface, thereby making it possible that the end products of the pathway, alpha-,omega-dicarboxylic FAs, are generally required for the cross-linking that ensures the integrity of the outer epidermal cell wall.
Kurdyukov
Sergey
S
Max-Planck-Institut für Züchtungsforschung, Carl von Linné Weg 10, 50829 Cologne, Germany.
Faust
Andrea
A
Trenkamp
Sandra
S
Bär
Sascha
S
Franke
Rochus
R
Efremova
Nadia
N
Tietjen
Klaus
K
Schreiber
Lukas
L
Saedler
Heinz
H
Yephremov
Alexander
A
D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics; D003998:Dicarboxylic Acids / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis / Q000096:biosynthesis* / Q000737:chemistry; D035264:Flowers / Q000166:cytology / Q000648:ultrastructure; D008055:Lipids; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D010641:Phenotype; D010802:Phylogeny; D019441:Plant Epidermis / Q000648:ultrastructure; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D004251:DNA Transposable Elements; D003998:Dicarboxylic Acids; D005227:Fatty Acids; D008055:Lipids; D012333:RNA, Messenger; C503530:hothead protein, Arabidopsis