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Novel candidate genes AuxRP and Hsp90 influence the chip color of potato tubers.

ABSTRACT: Potato (Solanum tuberosum L.) tubers exhibit significant variation in reducing sugar content directly after harvest, cold storage and reconditioning. Here, we performed QTL analysis for chip color, which is strongly influenced by reducing sugar content, in a diploid potato mapping population. Two QTL on chromosomes I and VI were detected for chip color after harvest and reconditioning. Only one region on chromosome VI was linked with cold-induced sweetening. Using the RT-PCR technique, we showed differential expression of the auxin-regulated protein (AuxRP) gene. The AuxRP transcript was presented in light chip color parental clone DG 97-952 and the RNA progeny of the bulk sample consisting of light chip color phenotypes after cold storage. This amplicon was absent in dark chip parental clone DG 08-26/39 and the RNA bulk sample of dark chip progeny. Genetic variation of AuxRP explained up to 16.6 and 15.2 % of the phenotypic variance after harvest and 3 months of storage at 4 °C, respectively. Using an alternative approach, the RDA-cDNA method was used to recognize 25 gene sequences, of which 11 could be assigned to potato chromosome VI. One of these genes, Heat-shock protein 90 (Hsp90), demonstrated higher mRNA and protein expression in RT-qPCR and western blotting assays in the dark chip color progeny bulk sample compared with the light chip color progeny bulk sample. Our study, for the first time, suggests that the AuxRP and Hsp90 genes are novel candidate genes capable of influencing the chip color of potato tubers.

SUBMITTER: Soltys-Kalina D

PROVIDER: S-EPMC4648990 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundStoring potato tubers at low temperatures minimizes sprouting and disease but can cause an accumulation of reducing sugars in a process called cold-induced sweetening. Tubers with increased amounts of reducing sugars produce dark-colored, bitter-tasting fried products with elevated amounts of acrylamide, a possible carcinogen. Vacuolar invertase (VInv), which converts sucrose produced by starch breakdown to glucose and fructose, is the key determinant of reducing sugar accumulation during cold-induced sweetening. In this study, wild-type tubers and tubers in which VInv expression was reduced by RNA interference were used to investigate time- and temperature-dependent changes in sugar contents, chip color, and expression of VInv and other genes involved in starch metabolism in tubers during long-term cold storage.ResultsVInv activities and tuber reducing sugar contents were much lower, and tuber sucrose contents were much higher, in transgenic than in wild-type tubers stored at 3-9°C for up to eight months. Large differences in VInv mRNA accumulation were not observed at later times in storage, especially at temperatures below 9°C, so differences in invertase activity were likely established early in the storage period and maintained by stability of the invertase protein. Sugar contents, chip color, and expression of several of the studied genes, including AGPase and GBSS, were affected by storage temperature in both wild-type and transgenic tubers. Though transcript accumulation for other sugar-metabolism genes was affected by storage temperature and duration, it was essentially unaffected by invertase silencing and altered sugar contents. Differences in stem- and bud-end sugar contents in wild-type and transgenic tubers suggested different compartmentalization of sucrose at the two ends of stored tubers.ConclusionsVInv silencing significantly reduced cold-induced sweetening in stored potato tubers, likely by means of differential VInv expression early in storage. Transgenic tubers retained sensitivity to storage temperature, and accumulated greater amounts of sucrose, glucose and fructose at 3°C than at 7-9°C. At each storage temperature, suppression of VInv expression and large differences in tuber sugar contents had no effect on expression of AGPase and GBSS, genes involved in starch metabolism, suggesting that transcription of these genes is not regulated by tuber sugar content.

Project description:This is a study to characterize gene expression profiles in stored Russet Burbank potato tubers. Tubers were harvested from commercial fields in the central sands region of Wisconsin in the fall of 2006. The tubers were put into storage at 55 degrees F for preconditioning and wound healing. Shortly after the temperature of the storage bin began to decrease, uniform, healthy tubers were selected for use in this microarray analysis. Tubers were at 53.6 degrees F at this time, and pieces of starch-storing tissue were collected for use as the reference sample. Other tubers were moved to temperature-controlled lockers and these were cooled gradually to either 48 or 40 degrees F following industry standard procedures. The expectation was that tubers held at 48 degrees would not have a significant accumulation of glucose and fructose, but that tubers cooled to 40 degrees would undergo low temperature sweetening and accumulate glucose and fructose to a degree that is unsuitable for processing. Three weeks later, when the locker temperatures were 48 degrees F and 41.5 degrees F, tissue samples were collected for RNA analysis. After another three weeks, samples were collected from tubers at 48 degrees F and 40 degrees F. At that time some tubers were moved from the 48 degree locker to the 40 degree locker in order to see if gene expression changes observed as a result of gradual cooling are similar to those that occur following a sudden decrease in temperature. Three weeks later, samples were collected from tubers held at 48 degrees F, tubers held at 40 degrees F, and from the tubers that were moved from 48 to 40 degrees F. At this time another set of tubers was transferred from 48 degrees to 40 degrees. Three weeks later the last samples were harvested from tubers held at 48 degrees F, from tubers held at 48 degrees F and from tubers that were transferred three weeks prior from 48 to 40 degrees. RNA was isolated from tissue extracted from three tubers. Keywords: Reference design

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Novel candidate genes AuxRP and Hsp90 influence the chip color of potato tubers.

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