CYP 77 A 19 and CYP 77 A 20 characterized from S olanum tuberosum oxidize fatty acids in vitro and partially restore the wild phenotype in an A rabidopsis thaliana cutin mutant

Cutin and suberin represent lipophilic polymers forming plant/environment interfaces in leaves and roots. Despite recent progress in A rabidopsis , there is still a lack on information concerning cutin and suberin synthesis, especially in crops. Based on sequence homology, we isolated two c DNA clones of new cytochrome P 450s, CYP 77 A 19 and CYP 77 A 20 from potato tubers ( S olanum tuberosum ). Both enzymes hydroxylated lauric acid ( C 12:0) on position ω ‐1 to ω ‐5. They oxidized fatty acids with chain length ranging from C 12 to C 18 and catalysed hydroxylation of 16‐hydroxypalmitic acid leading to dihydroxypalmitic (DHP) acids, the major C 16 cutin and suberin monomers. CYP 77 A 19 also produced epoxides from linoleic acid ( C 18:2). Exploration of expression pattern in potato by RT ‐q PCR revealed the presence of transcripts in all tissues tested with the highest expression in the seed compared with leaves. Water stress enhanced their expression level in roots but not in leaves. Application of methyl jasmonate specifically induced CYP 77 A 19 expression. Expression of either gene in the A rabidopsis null mutant cyp77a6‐1 defective in flower cutin restored petal cuticular impermeability. Nanoridges were also observed in CYP 77 A 20‐expressing lines. However, only very low levels of the major flower cutin monomer 10,16‐dihydroxypalmitate and no C 18 epoxy monomers were found in the cutin of the complemented lines. Our studies focuse on synthesis of cutin and suberin constituting the main barrier between plants and environment. Despite their fundamental role in the life of plants, the knowledge of enzymes and genes involved in their synthesis is still limited. The few data available mainly concern the model plant Arabidopsis thaliana. In the present work we identified and characterized in potato (Solanum tuberosum) two new cytochrome P450 dependant fatty acid hydroxylases. Our results support the hypothesis of their involvement in cutin and suberin synthesis and show that potato represents an alternative model plant for elucidation of protective envelopes synthesis in crops of great economic importance.