Functional analysis of the LACERATA gene of Arabidopsis provides evidence for different roles of fatty acid ω-hydroxylation in development

Abstract

We describe lacerata (lcr) mutants of Arabidopsis, which display various developmental abnormalities, including postgenital organ fusions, and report cloning of the LCR gene by using the maize transposon Enhancer͞Suppressor-mutator (En͞Spm). The pleiotropic mutant phenotype could be rescued by genetic complementation of lcr mutants with the wild-type LCR gene. The LCR gene encodes a cytochrome P450 monooxygenase, CYP86A8, which catalyzes -hydroxylation of fatty acids ranging from C12 to C18:1, as demonstrated by expression of the gene in yeast. Although palmitic and oleic acids were efficient substrates for LCR, 9,10-epoxystearate was not metabolized. Taken together with previous studies, our findings indicate that LCR-dependent -hydroxylation of fatty acids could be implicated in the biosynthesis of cutin in the epidermis and in preventing postgenital organ fusions. Strikingly, the same pathway seems to control trichome differentiation, the establishment of apical dominance, and senescence in plants.T he epidermis of plants is a composite tissue that comprises several cell types. Some of these, such as stoma cells, trichomes, and papilla cells, can be easily distinguished from the predominating pavement cells by their characteristic morphological features. Other cell types are not readily distinguishable, although they apparently perform specific functions. One example of this is given by epidermal cells on the adaxial side of carpels, which exhibit a unique contact response during elaboration of the pistil and are able to adhere and redifferentiate into parenchymatous cells. Another unique feature of these epidermal cells is their ability to adhere to the growing pollen tube and guide it to the embryo sac (1, 2). In contrast to animals, where selectively established cell adhesions are common and play an enormous role in development (3, 4), examples of regular cell adhesions in higher plants are rare, and indeed may be restricted to the processes cited above. In particular mutants in several plant species fusions of organs occur during development of the shoot, in a process that resembles the regular fusion of carpels. It is not yet known whether the same molecular mechanisms underlie all instances of cell fusions. By comparison with the epidermis cells of fused carpels, epidermis cells at sutures in fusion mutants do not alter their normal anticlinal plane of division and do not redifferentiate in response to the adhesion. Cell differentiation, however, is affected in at least two fusion mutants. The epidermis of crinkly4 (cr4) maize plants contains enlarged, occasionally spherical, cells, which can divide periclinally to give rise to multilayered sectors (5). In the fiddlehead ( fdh) mutant of Arabidopsis, the epidermis of rosette leaves displays a 2-fold reduction in the number of trichomes (6). These findings indicate a link between the altered cell differentiation in the epidermis and the fusion of organs in the mutants.By using transposon tagging, FDH and CR4, two genes that result in organ fusions when m...

Cloning and Characterization of the WAX2 Gene of Arabidopsis Involved in Cuticle Membrane and Wax Production

“…Fusion in wax2, cer10, and cer13 is less severe than that in wax1 and ded. Other Arabidopsis mutants that show postgenital fusion are ahd, bud, cod, fdh, hth, phd, thd (Lolle et al, 1998), and lcr (Wellesen et al, 2001). However, none of these mutants has altered visible wax deposition.…”

“…The CR4 gene was cloned and shown to encode a receptor-like kinase involved in the regulation of global aspects of leaf development rather than strictly cuticle membrane metabolism. Other genes were cloned whose predicted protein sequences suggest functions in the synthesis of cutin (the primary component of cuticle membrane); these genes include CYP86A1 , CYP94A1 , CYP94A2 , and LCR Tijet et al, 1998;LeBouquin et al, 1999;Wellesen et al, 2001). However, these genes have yet to be linked with cutin synthesis in planta.…”

Genome-Wide Identification of Genes Expressed in Arabidopsis Pistils Specifically along the Path of Pollen Tube Growth

“…These include LTPs, of which one proposed function is the transport of cutin monomers to the cell surface (Kader, 1996), and two genes previously implicated in the biosynthesis of cutin in epidermal cells of Arabidopsis: the At1g49430 gene, whose product, LACS2, exhibits long-chain acyl-CoA synthetase activity (Schnurr et al, 2004), and At4g00360 (CYP86A2), which shares 87% amino acid sequence similarity with the fatty acid v-hydroxylase LACERTA (LCR; CYP86A8; Wellesen et al, 2001).…”

Functional conservation and maintenance of expression pattern of FIDDLEHEAD-like genes in Arabidopsis and Antirrhinum

“…Orchestration of a number of pathways and cell-cell communication are necessary for proper differentiation of protodermal cells (Van Den Berg et al, 1997;Huelskamp and Schnittger, 1998). In Arabidopsis, studies on the FIDDLEHEAD (FDH), HIGH CARBON DIOXIDE (HIC), LACERATA (LCR) and WAX2/YORE-YORE genes have revealed a role for fatty acid metabolism in this process (Yephremov et al, 1999;Pruitt et al, 2000;Wellesen, 2001;Chen et al, 2003;Kurata et al, 2003). The FDH and HIC genes code for putative b-ketoacylCoA synthases of the FATTY ACID ELONGA-TION1 (FAE1) gene family, which consists of 21 genes in Arabidopsis (Lechelt-Kunze et al, 2003).…”