Induced expression of sucrose synthase and alcohol dehydrogenase I genes in phytoplasma‐infected grapevine plants grown in the field

Abstract

Interaction between phytoplasma and grapevine at the physiological level is still poorly understood, as are plant defence mechanisms against the pathogen. This study investigates the level of gene expression of three selected genes in a large number of grapevine plants belonging to six disease/cultivar groups (healthy Chardonnay, Bois noir-infected Chardonnay, Flavescence dorée-infected Barbera and Prosecco, and recovered Barbera and Prosecco). All plants were grown in vineyards in uncontrolled conditions in order to represent the physiology of disease as accurately as possible. Sucrose synthase was significantly upregulated in infected plants of all cultivars with the lowest P -values in cvs Chardonnay and Prosecco ( P < 0·001) and median fold-change around 2. This clearly indicates that carbohydrate metabolism changed in infected compared to healthy or recovered plants. Alcohol dehydrogenase I was significantly upregulated in infected relative to healthy Chardonnay plants ( P < 0·05) indicating that alcoholic fermentation, a sign of hypoxic conditions, was induced in infected plants. Heat shock protein 70 was upregulated in infected compared to recovered plants only in cv. Prosecco. Linear discriminant analysis showed that classification of samples into disease status groups based on gene expression was highly accurate (82%), indicating that the response of field-grown plants to phytoplasma infection at the level of expression of selected genes was so intensive and uniform that it was possible to detect it in grapevine plants regardless of natural variables.

Statistical modeling of long-term grapevine response to ‘Candidatus Phytoplasma solani’ infection in the field

“…We have previously shown that an accurate classification of plants as uninfected or infected with 'Ca. P. solani' is also possible with other tools, for example with a support vector machines algorithm (Hren et al 2009b). Although the results of such classification have been confirmed to be very accurate, they are without real applied value because the analysis is very laborious, requiring RT-qPCR analysis of 17 genes.…”

“…Pathogen abundance was assessed (Table 1) in the same samples as were collected for evaluation of host plant gene expression to ensure that phytoplasma was alive and active at the time of sampling. The expression of Stol11cDNAwas normalized to expression of COX and 18S rDNA reference genes and relatively quantified as previously described in detail (Hren et al 2009b). For the relative quantification, plant 24 was used as a calibration sample.…”

“…The RT-qPCR analysis of 21 selected genes was performed exactly as previously described (Hren et al 2009b). Among the genes that showed statistically significant differential expression between 'Ca.…”

“…Data was first analyzed using the Lightcycler 480 software (Roche). The standard curve method was used for quantification of relative gene expression (Hren et al 2009b), where the efficiency of amplification of each amplicon was extrapolated from the slope of the standard curve. The results of the gene expression analysis were calculated as numbers of copies relative to the geometrical mean of COX and 18S (Eukaryotic 18S rRNA TaqMan endogenous control, Life Technologies) copies.…”

Polymerase Chain Reaction for Phytoplasmas Detection

“…The most common symptoms of the infected plants are yellowing caused by the breakdown of chlorophyll and carotenoids, whose biosynthesis is also inhibited (21). Induced expression of sucrose synthase and alcohol dehydrogenase I genes in phytoplasma-infected grapevine plants grown in the field was also recently demonstrated (72).…”