Proteomic and selected metabolite analysis of grape berry tissues under well-watered and water-deficit stress conditions

Abstract

In order to investigate the unique contribution of individual wine grape (Vitis vinifera) berry tissues and water-deficit to wine quality traits, a survey of tissue-specific differences in protein and selected metabolites was conducted using pericarp (skin and pulp) and seeds of berries from vines grown under well-watered and water-deficit stress conditions. Of 1047 proteins surveyed from pericarp by 2-D PAGE, 90 identified proteins showed differential expression between the skin and pulp. Of 695 proteins surveyed from seed tissue, 163 were identified and revealed that the seed and pericarp proteomes were nearly completely distinct from one another. Water-deficit stress altered the abundance of approximately 7% of pericarp proteins, but had little effect on seed protein expression. Comparison of protein and available mRNA expression patterns showed that 32% pericarp and 69% seed proteins exhibited similar quantitative expression patterns indicating that protein accumulation patterns are strongly influenced by post-transcriptional processes. About half of the 32 metabolites surveyed showed tissue-specific differences in abundance with water-deficit stress affecting the accumulation of seven of these compounds. These results provide novel insights into the likely tissue-specific origins and the influence of water-deficit stress on the accumulation of key flavor and aroma compounds in wine.

Figure 1

2D-PAGE analysis of Vitis vinifera cv. Cabernet Sauvignon berry skin proteins. Proteins that exhibited a significant (p < 0.05) two-fold or greater change between the skin and pulp are indicated by circles and standard spot numbers on a representative gel. See Table 3 for detailed listing of proteins.

Figure 2

2D-PAGE analysis of Vitis vinifera cv. Cabernet Sauvignon berry pulp proteins. Proteins that exhibited a significant (p < 0.05) two-fold or greater change between the skin and pulp are indicated by circles and standard spot numbers on a representative gel. See Table 3 for detailed listing of proteins.

Figure 3

2D-PAGE analysis of Vitis vinifera cv. Cabernet Sauvignon berry seed proteins. Proteins that exhibited a significant (p < 0.05) two-fold or greater change between the seed and pericarp tissues are indicated by circles and standard spot numbers on a representative gel. See Table 4 for detailed listing of proteins. Inset: spot 7203 (arrow), which was more abundant in seed of well watered than water-deficit treated berries.

Figure 4

Spots whose abundance differed significantly (p < 0.05; two-fold or greater change) with water status. A) Pulp proteins more abundant under well-watered conditions. B) Pulp proteins more abundant under water-deficit conditions. C) Skin proteins more abundant under well watered conditions. D) Skin proteins more abundant under water-deficit conditions are indicated by circles and standard spot numbers on a representative gel. See Tables 5 and 6 for detailed listing of pulp and skin proteins, respectively.

Figure 5

Correlation of protein and mRNA abundance in different berry tissues. Values are expressed as log₂ ratio of abundance: A) in pulp vs. skin B) in seed vs. pericarp. Solid diamonds represent individual gene products following similar trends for both mRNA and protein expression.

Figure 6

Identification and quantitative differences of selected metabolites within different tissues: A) phenylpropanoids, B) amino acids, C) organics acids, and D) sugars. Skin (black bars), pulp (gray bars), seed (white bars). Up arrows indicate that the metabolite was significantly (ANOVA p<0.005, two-fold change or greater) more abundant than in tissues with a horizontal or arrow down. Horizontal arrows indicate that the metabolite was significantly (p<0.005, two-fold change or greater) less abundant than in tissues with an up arrow and more abundant than in tissues with a down arrow. Down arrows indicate that the metabolite was significantly (p<0.005, two-fold ratio change or greater) less abundant than in tissues with a horizontal or up arrow. Error bars represent standard deviation of the mean, n = 5.

Figure 7

Metabolites that differed significantly (ANOVA p< 0.05) between pulp derived from well watered and water-deficit treated vines. Asterisk (*) indicates metabolites that exhibited a two-fold or greater change in abundance. Error bars represent standard deviation of the mean, n = 5. Values within bars are the ratio relative to the internal standard (ribitol).

Figure 8. Enzymes and metabolites differentially expressed across tissues within a simplified flavonoid biosynthetic pathway

Underlined names indicate the enzymes or metabolites more abundant in skin; Boxed name indicates the metabolite more abundant in the seed.