Development of Kompetitive Allele Specific PCR markers for identification of persimmon varieties using genotyping-by-sequencing

BACKGROUND: Persimmon (Diospyros kaki Thunb.) is the most widely cultivated species of the genus Diospyros. In this study, genetic diversity and variations in persimmon genotypes were investigated using single nucleotide polymorphism (SNP) markers identified by genotyping-by-sequencing (GBS) analysis. RESULTS: Ninety-five persimmon accessions grown in the Pear Research Institute, National Institute Horticultural and Herbal Science, were sequenced using the Illumina Hiseq2500 platform and polymorphic SNPs were detected to develop molecular markers. These reliable SNPs were analyzed using the Kompetitive Allele Specific PCR (KASP) assay to discriminate among persimmon genotypes. GBS generated a total of 447,495,724 trimmed reads, of which 89.7% were raw reads. After demultiplexing and sequence quality trimming, 108,876,644 clean reads were mapped to the reference transcriptome. An average of 1,146,070 genotype reads were mapped. Filtering of raw SNPs in each sample led to selection of a total of 1,725,401 high-quality SNPs. The number of homozygous and heterozygous SNPs ranged from 1,933 to 6,834 and from 846 to 5,927, respectively. CONCLUSIONS: Of the 49 SNPs selected for development of an identification system for persimmons, 15 SNPs were used in the KASP assay to analyze 32 persimmon accessions. These KASP markers discriminated among all accessions.

Characterization of a F280N variant of L-arabinose isomerase from Geobacillus thermodenitrificans identified as a D-galactose isomerase.

The double-site variant (C450S-N475K) L-arabinose isomerase (L-AI) from Geobacillus thermodenitrificans catalyzes the isomerization of D-galactose to D-tagatose, a functional sweetener. Using a substrate-docking homology model, the residues near to D-galactose O6 were identified as Met186, Phe280, and Ile371. Several variants obtained by site-directed mutagenesis of these three residues were analyzed, and a triple-site (F280N) variant enzyme exhibited the highest activity for D-galactose isomerization. The k cat/K m of the triple-site variant enzyme for D-galactose was 2.1-fold higher than for L-arabinose, whereas the k cat/K m of the double-site variant enzyme for L-arabinose was 43.9-fold higher than for D-galactose. These results suggest that the triple-site variant enzyme is a D-galactose isomerase. The conversion rate of D-galactose to D-tagatose by the triple-site variant enzyme was approximately 3-fold higher than that of the double-site variant enzyme for 30 min. However, the conversion yields of L-arabinose to L-ribulose by the triple-site and double-site variant enzymes were 10.6 and 16.0 % after 20 min, respectively. The triple-site variant enzyme exhibited increased specific activity, turnover number, catalytic efficiency, and conversion rate for D-galactose isomerization compared to the double-site variant enzyme. Therefore, the amino acid at position 280 determines the substrate specificity for D-galactose and L-arabinose, and the triple-site variant enzyme has the potential to produce D-tagatose on an industrial scale.

γ-Dodecelactone production from safflower oil via 10-hydroxy-12(Z)-octadecenoic acid intermediate by whole cells of Candida boidinii and Stenotrophomonas nitritireducens.

Candida boidinii was selected as a γ-dodecelactone producer because of the highest production of γ-dodecelactone from 10-hydroxy-12(Z)-octadecenoic acid among the 11 yeast strains tested. Under the reaction conditions of pH 5.5 and 25 °C with 5 g/L 10-hydroxy-12(Z)-octadecenoic acid and 30 g/L cells, whole C. boidinii cells produced 2.1 g/L γ-dodecelactone from 5 g/L 10-hydroxy-12(Z)-octadecenoic acid after 6 h, with a conversion yield of 64% (mol/mol) and a volumetric productivity of 350 mg/L/h. The production of γ-dodecelactone from safflower oil was performed by lipase hydrolysis reaction and two-step whole-cell biotransformation using Stenotrophomonas nitritireducens and C. boidinii. γ-Dodecelactone at 1.88 g/L was produced from 7.5 g/L safflower oil via 5 g/L 10-hydroxy-12(Z)-octadecenoic acid intermediate by these reactions after 8 h of reaction time, with a volumetric productivity of 235 mg/L/h and a conversion yield of 25% (w/w). To the best of the authors' knowledge, this is the highest volumetric productivity and conversion yield reported to date for the production of γ-lactone from natural oils.