title: Two fatty acid desaturases, STEAROYL-ACYL CARRIER PROTEIN Δ9-DESATURASE6 and FATTY ACID DESATURASE3, are involved in drought and hypoxia stress signaling in Arabidopsis crown galls.
abstract: Agrobacterium tumefaciens-derived crown galls of Arabidopsis (Arabidopsis thaliana) contain elevated levels of unsaturated fatty acids and strongly express two fatty acid desaturase genes, ω3 FATTY ACID DESATURASE3 (FAD3) and STEAROYL-ACYL CARRIER PROTEIN Δ9-DESATURASE6 (SAD6). The fad3-2 mutant with impaired α-linolenic acid synthesis developed significantly smaller crown galls under normal, but not under high, relative humidity. This strongly suggests that FAD3 plays a role in increasing drought stress tolerance of crown galls. SAD6 is a member of the SAD family of as yet unknown function. Expression of the SAD6 gene is limited to hypoxia, a physiological condition found in crown galls. As no sad6 mutant exists and to link the function of SAD6 with fatty acid desaturation in crown galls, the lipid pattern was analyzed of plants with constitutive SAD6 overexpression (SAD6-OE). SAD6-OE plants contained lower stearic acid and higher oleic acid levels, which upon reduction of SAD6 overexpression by RNA interference (SAD6-OE-RNAi) regained wild-type-like levels. The development of crown galls was not affected either in SAD6-OE or SAD6-OE-RNAi or by RNA interference in crown galls. Since biochemical analysis of SAD6 in yeast (Saccharomyces cerevisiae) and Escherichia coli failed, SAD6 was ectopically expressed in the background of the well-known suppressor of salicylic acid-insensitive2 (ssi2-2) mutant to confirm the desaturase function of SAD6. All known ssi2-2 phenotypes were rescued, including the high stearic acid level. Thus, our findings suggest that SAD6 functions as a Δ9-desaturase, and together with FAD3 it increases the levels of unsaturated fatty acids in crown galls under hypoxia and drought stress conditions.
authors.affiliation: Department of Molecular Plant Physiology and Biophysics , Julius-von-Sachs-Institute, University of Wuerzburg, D-97082 Wuerzburg, Germany.
authors.forename: Joern
authors.initials: J
authors.lastname: Klinkenberg
authors.forename: Hanna
authors.initials: H
authors.lastname: Faist
authors.forename: Stefanie
authors.initials: S
authors.lastname: Saupe
authors.forename: Sophie
authors.initials: S
authors.lastname: Lambertz
authors.forename: Markus
authors.initials: M
authors.lastname: Krischke
authors.forename: Nadja
authors.initials: N
authors.lastname: Stingl
authors.forename: Agnes
authors.initials: A
authors.lastname: Fekete
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Mueller
authors.forename: Ivo
authors.initials: I
authors.lastname: Feussner
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
authors.forename: Rosalia
authors.initials: R
authors.lastname: Deeken
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia / Q000235:genetics; D002736:Chloroplasts / Q000201:enzymology; D055864:Droughts; D004721:Endoplasmic Reticulum / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006813:Humidity; D056626:Inflorescence / Q000201:enzymology / Q000235:genetics; D009154:Mutation / Q000235:genetics; D010743:Phospholipids / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D010941:Plant Tumors / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D005227:Fatty Acids; D010743:Phospholipids; D044943:Fatty Acid Desaturases; C000592237:SAD6 protein, Arabidopsis; C474651:fad3 protein, Arabidopsis