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.

Keywords: Auxin-regulated protein (AuxRP) gene; DArT markers; Heat-shock protein 90 (Hsp90) gene; Quantitative trait loci; Reducing sugar content; Solanum tuberosum.

Fig. 1

Expression profiling of AuxRP in parental clones P1 (DG 97-952, chip color 7) and P2 (DG 08-26/39, chip color 4), and bulk samples L^I (chip color 8–9) and D^I (chip color 1–3) after cold storage (CS). M—molecular weight marker (100-bp DNA ladder)

Fig. 2

RDA-cDNA amplicons in 1.5 % agarose gels after the first (SH^I), second (SH^II), third (SH^III) and fourth (SH^IV) rounds of subtractive hybridization. The 250- and 300-bp fragments selected in the SH^IV round are marked by arrows. M1—1-kb DNA ladder, M2—100-bp DNA ladder, L^II—genotypes with light chip color as a TESTER, D^II—genotypes with light chip color as a DRIVER

Fig. 3

a Expression level of the Hsp90 gene in tubers after cold storage (CS); ns non-significant differences between parental clones (Student’s t test); a and b homogenous groups between bulk samples L^II and D^II (Tukey’s test). b Amounts of Hsp90-1 and Hsp90-2 protein isoforms in tubers after cold storage (CS); Marker—Prosieve^® QuadColor™ Protein Marker. Parental clones: DG 97-952 (chip color 7) and DG 08-26/39 (chip color 4); bulk samples: L^II (chip color 8–9) and D^II (chip color 1–3)