Effect of light exposure on linalool biosynthesis and accumulation in grape berries

Figures & data

Fig. 1. Representative genes in MEP and MVA pathway.

Notes: HMG-CoA, 3-hydroxy-3-methylglutaryl-CoA; MVA, mevalonate; IPP, isopentenyl pyrophosphate; DMAPP, dimethylallyl pyrophosphate; FPP, farnesyl pyrophosphate; GA-3P, glyceraldehyde 3-phosphate; DXP, 1-deoxy-D-xylulose 5-phosphate; MEP, methylerythritol 4-phosphate; GPP, geranyl pyrophosphate; HMGR, HMG-CoA reductase; FPPS, FPP synthase; DXS, DXP synthase; DXR, DXP reductoisomerase; GPPS, GPP synthase.

Fig. 2. Organ-specific accumulation of linalool and genes involved in terpenoid biosynthesis.

Notes: (A) Contents of total linalool in berries. (B) Analysis of MEP pathway gene expression in berries. The black, dark grey, light grey, and white bars indicate DXS, DXR, GPPS, and linalool synthase, respectively. (C) Analysis of MVA pathway gene expression in berries. The light grey and white bars indicate HMGR and FPPS, respectively. Berries were harvested on September 15, 2012. The values are means±standard deviation of three replicates. Fw and N.D. indicate fresh weight and not detected, respectively. Statistical analyses were performed by Mann–Whitney U-test followed by Kruskal Wallis H-test, and the asterisks indicate statistically significant differences (p < 0.05) with the values of the flesh.

Fig. 3. Effects of light reduction on linalool accumulation and expression levels of genes involved in terpenoid biosynthesis.

Notes: (A) The bunches of Sauvignon blanc grapes were covered with three films, Control, UV-block, and Shade, and berries were randomly sampled during the 2012 growing season. (B) Total soluble solid and (C) total linalool contents in juice. Open circles, filled circles, and open triangles indicate Control-, UV-block-, and Shade-covered grapes, respectively. (D) Analysis of MEP pathway gene expression in skin of grapes on September 1, 2012. The black, dark grey, light grey, and white bars indicate DXS, DXR, GPPS, and linalool synthase, respectively. (E) Gene expression analysis of MVA pathway in skin of grapes on September 1, 2012. The light grey and white bars indicate HMGR and FPPS, respectively. The values are means ± standard deviation of three replicates. Statistical analyses were performed by Mann–Whitney U-test followed by Kruskal Wallis H-test, and the asterisks indicate statistically significant differences (p < 0.05) with the values of the control.

Table 1. Light exposure condition of Sauvignon blanc clusters covered with films.

Type of film	PAR level (μmol m^−2 s^−1)	UV illuminance (μW cm^−2)	Full-light spectral illuminance (klux)
Control	1612 ± 28	373 ± 12	89 ± 0.72
UV-block	1660 ± 23	182 ± 8.5*	83 ± 0.74
Shade	2.0 ± 0.24*	3.2 ± 0.39*	1.0 ± 0.057*

Notes: The values are means  ±  standard deviation of 20 replicates. Statistical analyses were performed by Mann–Whitney U-test followed by Kruskal Wallis H-test, and the asterisks indicate statistically significant differences (p < 0.05) with the values of the control.

Fig. 4. Effects of reflective sheets on total linalool accumulation and expression levels of genes involved in terpenoid biosynthesis during 2012 growing season.

Notes: Reflective sheets were placed on August 8 2012, and berries were randomly sampled during the 2012 growing season. (A) Total soluble solid content, (B) titratable acidity, and (C) total linalool content in the juice throughout the growing season. (D-I) Analysis of MEP and MVA pathway gene expressions in skin (D, DXS; E, DXR; F, GPPS; G, linalool synthase; H, HMGR; I, FPPS). Open and filled circles indicate control grapes and reflected-light-exposed grapes, respectively. The values are means±standard deviation of three replicates. Statistical analysis were performed by Mann–Whitney U-test, and the asterisks indicate statistically significant differences (p < 0.05) with the values of the control.