Expression Profiles of Genes Involved in the Carotenoid Biosynthetic Pathway in Yellow-Fleshed Potato Cultivars (Solanum tuberosum L.) from South Korea

Abstract

Efforts are being made to identify a parental cultivar suitable for metabolic engineering of potato (Solanum tuberosum L.) that will elevate total carotenoid content or produce a specific type of carotenoid. As an initial step in this search, we performed high performance liquid chromatography analyses and comparisons among gene expression profiles for several cultivars domesticated or bred in South Korea. Here, the dark yellow-fleshed "Golden Valley" contained the highest level of total carotenoids (23.8 μg g −1 dry weight (DW)), which was 1.7-to 3.7-fold higher than those measured in other cultivars. The predominant carotenoids in "Golden Valley" were lutein (40.3% of the total), violaxanthin (29.8%), and β-carotene (8.8%), with only a trace amount of zeaxanthin (0.02%) being detected. Levels of lutein and β-carotene in that cultivar were significantly higher than in the others. Interestingly, relatively high amounts of violaxanthin were accumulated in all cultivars, ranging from 15.9% (1.0 μg g −1 DW in "Jowon") to 61.7% (8.2 μg g −1 DW in "Dejima"). In accordance with the relatively high content of total carotenoids in "Golden Valley", remarkably elevated transcripts were also accumulated for most of the genes involved in the carotenoid biosynthetic pathway. In particular, genes encoding enzymes for the first three steps of carotenogenesis-phytoene synthase, phytoene desaturase, and ζ-carotene desaturase-were most actively expressed. A relatively high level of transcript for the carotene hydroxylase (Chy2) gene was detected in all cultivars, including "Jowon", which had accumulated the lowest amount of total carotenoids. In contrast, almost no transcripts were detected for carotene isomerase (CrtIso) and Chy1 in any of these cultivars. Our preliminary results suggest that "Golden Valley" is an excellent candidate for metabolic engineering that further increases its content of specific carotenoids, e.g., β-carotene and astaxanthin.

Levels of potential bioactive compounds including carotenoids, vitamin C and phenolic compounds, and expression of their cognate biosynthetic genes vary significantly in different varieties of potato (Solanum tuberosum L.) grown under uniform cultural conditions

“…A similar correlation in early developing tubers was found by Payyavula et al , but only for PSY2 gene expression, with PSY1 showing no specific trend . Partially contradicting these reports, another study with mature tubers found that PSY1 and PSY2 gene expression was highest in the potato variety accumulating more carotenoids, finding also a correlation between transcript levels and carotenoid content …”

“…32 Partially contradicting these reports, another study with mature tubers found that PSY1 and PSY2 gene expression was highest in the potato variety accumulating more carotenoids, finding also a correlation between transcript levels and carotenoid content. 52 Phytoene synthase is generally considered the most important regulatory enzyme in the pathway, and transgenic potato plants expressing a bacterial gene encoding phytoene synthase have produced increases in total carotenoid content in tubers and changes in the carotenoid profile, which indicate that phytoene synthase is a rate-limiting step in carotenoid production in tubers. No concomitant increase in the expression of the major carotenoid biosynthetic genes was detected, 53 underlining the complexity of the regulation of carotenoid synthesis and accumulation.…”

Identification of alleles of carotenoid pathway genes important for zeaxanthin accumulation in potato tubers

“…This allele shows higher expression than the other two alleles segregating in the C×E population (Kloosterman et al 2010 ). Goo et al ( 2009 ) also observed a higher expression level of Chy2 associated with yellow flesh colour in a small number of potato cultivars.…”

Overexpression of the sweet potato IbOr gene results in the increased accumulation of carotenoid and confers tolerance to environmental stresses in transgenic potato

“…To analyze the composition of carotenoids, HPLC analyses were carried out as previously described [31][32][33]. Briefly, 250 mg of the lyophilized samples were homogenized in a pre-chilled mortar and a pestle with 15 mL of acetone (0.01% butylated hydroxytoluene, BHT), sea sand, Na 2 SO 4 , and NaHCO 3 .…”