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Novel candidate genes influencing natural variation in potato tuber cold sweetening identified by comparative proteomics and association mapping.

Fischer M, Schreiber L, Colby T, Kuckenberg M, Tacke E, Hofferbert HR, Schmidt J, Gebhardt C - BMC Plant Biol. (2013)

Bottom Line: The molecular basis of CIS in potato tubers is of interest not only in basic research on plant adaptation to environmental stress but also in applied research, since high amounts of reducing sugars affect negatively the quality of processed food products such as potato chips.We compared by two-dimensional polyacrylamide gel electrophoresis the tuber proteomes of cultivars highly diverse for CIS.Novel SNP's diagnostic for increased tuber starch content, starch yield and chip quality were identified, which are useful for selecting improved potato processing cultivars.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Plant Breeding and Genetics, Max-Planck-Institute for Plant Breeding Research, Cologne, Germany. fischer@mpipz.mpg.de

ABSTRACT

Background: Higher plants evolved various strategies to adapt to chilling conditions. Among other transcriptional and metabolic responses to cold temperatures plants accumulate a range of solutes including sugars. The accumulation of the reducing sugars glucose and fructose in mature potato tubers during exposure to cold temperatures is referred to as cold induced sweetening (CIS). The molecular basis of CIS in potato tubers is of interest not only in basic research on plant adaptation to environmental stress but also in applied research, since high amounts of reducing sugars affect negatively the quality of processed food products such as potato chips. CIS-tolerance varies considerably among potato cultivars. Our objective was to identify by an unbiased approach genes and cellular processes influencing natural variation of tuber sugar content before and during cold storage in potato cultivars used in breeding programs. We compared by two-dimensional polyacrylamide gel electrophoresis the tuber proteomes of cultivars highly diverse for CIS. DNA polymorphisms in genomic sequences encoding differentially expressed proteins were tested for association with tuber starch content, starch yield and processing quality.

Results: Pronounced natural variation of CIS was detected in tubers of a population of 40 tetraploid potato cultivars. Significant differences in protein expression were detected between CIS-tolerant and CIS-sensitive cultivars before the onset as well as during cold storage. Identifiable differential proteins corresponded to protease inhibitors, patatins, heat shock proteins, lipoxygenase, phospholipase A1 and leucine aminopeptidase (Lap). Association mapping based on single nucleotide polymorphisms supported a role of Lap in the natural variation of the quantitative traits tuber starch and sugar content.

Conclusions: The combination of comparative proteomics and association genetics led to the discovery of novel candidate genes for influencing the natural variation of quantitative traits in potato tubers. One such gene was a leucine aminopeptidase not considered so far to play a role in starch sugar interconversion. Novel SNP's diagnostic for increased tuber starch content, starch yield and chip quality were identified, which are useful for selecting improved potato processing cultivars.

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Correlation between mean protein spot intensity and reducing sugar content (RSC) in 40 cultivars without cold treatment. (A) Representative pattern of tuber proteins obtained by 2D-PAGE. Numbered arrows point to the five spots with significant correlation between mean spot intensity and RSC (Table 1). (B-F) Correlation plots of the logarithmic values of mean spot intensity versus RSC. Plots B, C, D, E and F correspond to spots 1, 2, 3, 4 and 5, respectively. Framed numbers indicate potato cultivars listed in Additional file 1: Table S1.
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Figure 2: Correlation between mean protein spot intensity and reducing sugar content (RSC) in 40 cultivars without cold treatment. (A) Representative pattern of tuber proteins obtained by 2D-PAGE. Numbered arrows point to the five spots with significant correlation between mean spot intensity and RSC (Table 1). (B-F) Correlation plots of the logarithmic values of mean spot intensity versus RSC. Plots B, C, D, E and F correspond to spots 1, 2, 3, 4 and 5, respectively. Framed numbers indicate potato cultivars listed in Additional file 1: Table S1.

Mentions: Total soluble protein of tubers of the 40 cultivars before cold treatment was separated by 2D-PAGE. An average of 226 protein spots was detected per gel (data not shown). Twenty six protein spots were selected based on being present in more than 70% of all gels of the 40 cultivars including biological replicates, and quantified by measuring spot intensity. The data for mean RSC and spot intensities are provided in Additional file 2: Table S2. The spot intensity of five proteins correlated significantly (p < 0.05) with RSC (Figure 2, Table 1). The most significant correlation was found for a protein identified as ‘putative Kunitz-type tuber invertase inhibitor’ (Figure 2F, Table 1, Additional file 3: Table S3). Decreasing protein spot intensity correlated with increasing RSC. Negative correlation coefficients were also obtained for two proteins identified as ‘miraculin’ and ‘potato proteinase inhibitor class II’ (Figure 2D and E, Table 1, Additional file 3: Table S3). Two further proteins spots, both identified as ‘granule bound starch synthase’ were positively correlated with RSC (Figure 2B and C, Table 1, Additional file 3: Table S3).


Novel candidate genes influencing natural variation in potato tuber cold sweetening identified by comparative proteomics and association mapping.

Fischer M, Schreiber L, Colby T, Kuckenberg M, Tacke E, Hofferbert HR, Schmidt J, Gebhardt C - BMC Plant Biol. (2013)

Correlation between mean protein spot intensity and reducing sugar content (RSC) in 40 cultivars without cold treatment. (A) Representative pattern of tuber proteins obtained by 2D-PAGE. Numbered arrows point to the five spots with significant correlation between mean spot intensity and RSC (Table 1). (B-F) Correlation plots of the logarithmic values of mean spot intensity versus RSC. Plots B, C, D, E and F correspond to spots 1, 2, 3, 4 and 5, respectively. Framed numbers indicate potato cultivars listed in Additional file 1: Table S1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750364&req=5

Figure 2: Correlation between mean protein spot intensity and reducing sugar content (RSC) in 40 cultivars without cold treatment. (A) Representative pattern of tuber proteins obtained by 2D-PAGE. Numbered arrows point to the five spots with significant correlation between mean spot intensity and RSC (Table 1). (B-F) Correlation plots of the logarithmic values of mean spot intensity versus RSC. Plots B, C, D, E and F correspond to spots 1, 2, 3, 4 and 5, respectively. Framed numbers indicate potato cultivars listed in Additional file 1: Table S1.
Mentions: Total soluble protein of tubers of the 40 cultivars before cold treatment was separated by 2D-PAGE. An average of 226 protein spots was detected per gel (data not shown). Twenty six protein spots were selected based on being present in more than 70% of all gels of the 40 cultivars including biological replicates, and quantified by measuring spot intensity. The data for mean RSC and spot intensities are provided in Additional file 2: Table S2. The spot intensity of five proteins correlated significantly (p < 0.05) with RSC (Figure 2, Table 1). The most significant correlation was found for a protein identified as ‘putative Kunitz-type tuber invertase inhibitor’ (Figure 2F, Table 1, Additional file 3: Table S3). Decreasing protein spot intensity correlated with increasing RSC. Negative correlation coefficients were also obtained for two proteins identified as ‘miraculin’ and ‘potato proteinase inhibitor class II’ (Figure 2D and E, Table 1, Additional file 3: Table S3). Two further proteins spots, both identified as ‘granule bound starch synthase’ were positively correlated with RSC (Figure 2B and C, Table 1, Additional file 3: Table S3).

Bottom Line: The molecular basis of CIS in potato tubers is of interest not only in basic research on plant adaptation to environmental stress but also in applied research, since high amounts of reducing sugars affect negatively the quality of processed food products such as potato chips.We compared by two-dimensional polyacrylamide gel electrophoresis the tuber proteomes of cultivars highly diverse for CIS.Novel SNP's diagnostic for increased tuber starch content, starch yield and chip quality were identified, which are useful for selecting improved potato processing cultivars.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Plant Breeding and Genetics, Max-Planck-Institute for Plant Breeding Research, Cologne, Germany. fischer@mpipz.mpg.de

ABSTRACT

Background: Higher plants evolved various strategies to adapt to chilling conditions. Among other transcriptional and metabolic responses to cold temperatures plants accumulate a range of solutes including sugars. The accumulation of the reducing sugars glucose and fructose in mature potato tubers during exposure to cold temperatures is referred to as cold induced sweetening (CIS). The molecular basis of CIS in potato tubers is of interest not only in basic research on plant adaptation to environmental stress but also in applied research, since high amounts of reducing sugars affect negatively the quality of processed food products such as potato chips. CIS-tolerance varies considerably among potato cultivars. Our objective was to identify by an unbiased approach genes and cellular processes influencing natural variation of tuber sugar content before and during cold storage in potato cultivars used in breeding programs. We compared by two-dimensional polyacrylamide gel electrophoresis the tuber proteomes of cultivars highly diverse for CIS. DNA polymorphisms in genomic sequences encoding differentially expressed proteins were tested for association with tuber starch content, starch yield and processing quality.

Results: Pronounced natural variation of CIS was detected in tubers of a population of 40 tetraploid potato cultivars. Significant differences in protein expression were detected between CIS-tolerant and CIS-sensitive cultivars before the onset as well as during cold storage. Identifiable differential proteins corresponded to protease inhibitors, patatins, heat shock proteins, lipoxygenase, phospholipase A1 and leucine aminopeptidase (Lap). Association mapping based on single nucleotide polymorphisms supported a role of Lap in the natural variation of the quantitative traits tuber starch and sugar content.

Conclusions: The combination of comparative proteomics and association genetics led to the discovery of novel candidate genes for influencing the natural variation of quantitative traits in potato tubers. One such gene was a leucine aminopeptidase not considered so far to play a role in starch sugar interconversion. Novel SNP's diagnostic for increased tuber starch content, starch yield and chip quality were identified, which are useful for selecting improved potato processing cultivars.

Show MeSH
Related in: MedlinePlus