Genome-wide analysis of FATA associated with drought tolerance in tetraploid potato (Solanum tuberosum)

The cuticle represents the outer most protective barrier against biotic and abiotic stresses. It is composed of cutin and waxes and protects plants from desiccation, UV, cold, mechanical stresses, and pathogens. GWAS/BSAseq combined with SeqSNP analyses in an association panel of 34 potato cultivars had revealed that the acyl-ACP thioesterase FATA (Soltu.DM.06G033680.1) is significantly associated with drought tolerance in potato. Apart from three FATB genes, only one FATA gene is present in potato that has the highest homology to FATA2 in Arabidopsis. FATA is responsible for the export of C18:1 fatty acid from chloroplast into cytosol, which is necessary for the biosynthesis of cutin. A knockout mutant of AtFATA2 was analyzed with regard to the cuticle permeability and to drought tolerance as well as recovery. Loss of FATA function leads to higher sensibility to water deficit in Arabidopsis, but to no change in recovery. The increased permeability of the cuticle in the fata2 knockout mutant as shown indirectly by higher chlorophyll leaching might play a role in this. Haplotypes for FATA were identified for the two potato cultivars Albatros and Désirée. All Désirée haplotypes and Albatros haplotypes 1, 3 and 4 were also revealed by former potato pan genome studies, while Albatros haplotype 2 is unique and has not been described before. Protein models were developed to investigate the influence of different SNPs in the haplotypes on the predicted protein structure and especially the substrate cavity. In potato, protein modeling suggests that only the hypothetical isoform B of FATA might be able to process oleoyl-ACP, but not hypothetical isoform A. However, this hypothesis needs to be verified by enzyme activity assays.