Determining the Effects of Light on the Fruit Peel Quality of Photosensitive and Nonphotosensitive Eggplant

Abstract

With the development of facility agriculture, low-light stress is a prominent problem and a popular research topic currently. In this study, transcriptome analysis was used to analyze the genes in the fruit peel of photosensitive and nonphotosensitive eggplant and to explore the mechanism of changes in fruit color, texture, hormone content, aroma, and taste of these two different types of eggplant. We identified 51, 65, 66, and 66 genes involved in synthesizing anthocyanins, texture, hormone content, and aroma and flavor, respectively, in the two different types of eggplant based on the variation in gene expression trends in the fruit peel. These results provide a basis for further analysis of the molecular mechanism underlying the regulatory processes in eggplant fruits under low-light stress.

Keywords: eggplant; light; nonphotosensitive; photosensitive; transcriptome.

Figure 1

Changes in the appearance and genes of two eggplant varieties after bagging and illumination. (A) Changes in the appearance of nonphotosensitive eggplant after shading and illumination; (B) changes in the appearance of photosensitive eggplant after shading and illumination; and (C) changes in differentially expressed genes in the six comparison groups (both upregulated and downregulated).

Figure 2

GO enrichment circle diagram of the six comparison groups. The first circle: enrichment of the first 20 GO terms; the coordinate ruler for the gene number is outside the circle. Different colors represent different ontologies. The second circle: the number and Q value of the GO term in the background gene. The more genes present, the longer the bar, the smaller the Q value, and the redder the color. The third circle: bar chart of the proportion of upregulated genes; dark purple represents the proportion of upregulated genes, and light purple represents the proportion of downregulated genes. Specific values are shown below. The fourth circle: Rich Factor value of each GO term (the number of different genes in the GO term divided by all the numbers) and background grid lines, where each grid represents 0.1 ((A) comparison group CK1-P vs. T1-P; (B) comparison group T1-P vs. T2-P; (C) comparison group CK1-NP vs. T1-NP; (D) comparison group T1-NP vs. T2-NP; (E) comparison group T1-P vs. T1-NP; and (F) comparison group T2-P vs. T2-NP).

Figure 3

KEGG enrichment bubble plot. The first 20 pathways with the smallest Q values were used for the plot, with pathway as the ordinate and enrichment factor as the abscissa (the differentially expressed genes in this pathway are divided into groups based on the numbers shown). The size indicates the number, and the redder the color is, the smaller the Q value ((A) comparison group CK1-P vs. T1-P; (B) comparison group T1-P vs. T2-P; (C) comparison group CK1-NP vs. T1-NP; (D) comparison group T1-NP vs. T2-NP; (E) comparison group T1-P vs. T1-NP; and (F) comparison group T2-P vs. T2-NP).

Figure 4

Effects of shading and light on gene expression and signal transduction related to eggplant peel color. (A) Venn diagram showing differentially expressed genes related to eggplant peel color in the six comparison groups (S1: CK1-P vs. T1-P; S2: T1-P vs. T2-P; S3: CK1-NP vs. T1-NP; S4: T1-NP vs. T2-NP; S5: T1-P vs. T1-NP; S6: T2-P vs. T2-NP); (B) Chalcone isomerase (CHS); (C) Chalcone isomerase (CHI); (D) Dihydroflavonol 4-reductase (DFR); (E) Anthocyanin synthase (ANS); (F) 4-Coumarate--CoA ligase 2 (4CL2); (G) Anthocyanin-related transcription factor TT8; (H) 3-O-glucosyltransferase (3GT); (I) E3 ubiquitin-protein ligase (COP1); (J) Flavanone 3-hydroxylase (F3′H); (K) Flavonoid 3′,5′-hydroxylase (F3′5′H); and (L) Transcription factor MYB1. ((B–L): The x-axis represents different eggplant groups, and the y-axis represents FPKM values); the error bar represents the degree of dispersion of the gene expression data itself, as follows.

Figure 5

Effects of shading and light on gene expression and signal transduction related to eggplant peel texture. (A) Venn diagram showing differentially expressed genes related to eggplant peel texture in the six comparison groups (S1: CK1-P vs. T1-P; S2: T1-P vs. T2-P; S3: CK1-NP vs. T1-NP; S4: T1-NP vs. T2-NP; S5: T1-P vs. T1-NP; and S6: T2-P vs. T2-NP); (B) Cinnamyl alcohol dehydrogenase (CAD); (C) Polygalacturonase (PG); (D) Pectinesterase inhibitor 12 (PME12); (E) Beta-amylase 3 (BAM3); (F) Beta-amyrin synthase (BAS); (G) Glucan endo-1,3-beta-glucosidase (GLUB); (H) Cellulose synthase (CES); and (I) Xyloglucan hydrolase protein 24 (XTH24). ((B–I): The X-axis represents different eggplant groups, and the Y-axis represents FPKM values).

Figure 6

Effects of shading and light on gene expression and signal transduction related to eggplant peel hormones. (A) Venn diagram showing differentially expressed genes related to eggplant peel hormones in the six comparison groups (S1: CK1-P vs. T1-P; S2: T1-P vs. T2-P; S3: CK1-NP vs. T1-NP; S4: T1-NP vs. T2-NP; S5: T1-P vs. T1-NP; S6: T2-P vs. T2-NP); (B) Short-chain dehydrogenase 1 (SDR1); (C) Methyl jasmonate esterase (MJE); (D) Phenylalanine ammonia-lyase (PAL); (E) Auxin-responsive protein; (F) Gibberellin-regulated protein (GASA); (G) Ethylene-responsive transcription factor (ERF); (H) Growth-regulating factor 1 (GRF1); and (I) 1-aminocyclopropane-1-carboxylate oxidase (ACO). ((B–I): The X-axis represents different eggplant groups, and the Y-axis represents FPKM values).

Figure 7

Effects of shading and light on gene expression and signal transduction related to eggplant peel flavor and aromatic compounds. (A) Venn diagram showing differentially expressed genes related to eggplant peel flavor and aroma in the six comparison groups (S1: CK1-P vs. T1-P; S2: T1-P vs. T2-P; S3: CK1-NP vs. T1-NP; S4: T1-NP vs. T2-NP; S5: T1-P vs. T1-NP; S6: T2-P vs. T2-NP); (B) Phenylalanine ammonia-lyase (PAL); (C) Cinnamyl alcohol dehydrogenase 1 (CAD1); (D) (+)-neomenthol dehydrogenase ((+)-ND); (E) Tropinone reductase (TR); (F) Glyceraldehyde-3-phosphate dehydrogenase B (GAPB); (G) Bidirectional sugar transporter (SWEET); (H) Alcohol dehydrogenase 7 (AD7); and (I) 8-Hydroxygeraniol dehydrogenase (8HGO). ((B–I): The X-axis represents different eggplant groups, and the Y-axis represents FPKM values).

Figure 8

Model of genetic changes in response to shading and light during eggplant peel ripening. By comparing the differentially expressed genes between the two varieties of eggplant under shading and illumination, we found differences in several key genes related to color, texture, plant hormones, flavor, and aroma during eggplant peel ripening. (The blue arrow represents downregulation; the red arrow represents upregulation; the genes in the red icon are associated with eggplant color; the genes in the yellow icon are associated with eggplant texture; the genes in the green icon are associated with eggplant plant hormones; the genes in the blue icon are associated with eggplant flavor and aroma).