Gene expression profiles predictive of cold-induced sweetening in potato.

Cold storage (2-4 °C) used in potato production to suppress diseases and sprouting during storage can result in cold-induced sweetening (CIS), where reducing sugars accumulate in tuber tissue leading to undesirable browning, production of bitter flavors, and increased levels of acrylamide with frying. Potato exhibits genetic and environmental variation in resistance to CIS. The current study profiles gene expression in post-harvest tubers before cold storage using transcriptome sequencing and identifies genes whose expression is predictive for CIS. A distance matrix for potato clones based on glucose levels after cold storage was constructed and compared to distance matrices constructed using RNA-seq gene expression data. Congruence between glucose and gene expression distance matrices was tested for each gene. Correlation between glucose and gene expression was also tested. Seventy-three genes were found that had significant p values in the congruence and correlation tests. Twelve genes from the list of 73 genes also had a high correlation between glucose and gene expression as measured by Nanostring nCounter. The gene annotations indicated functions in protein degradation, nematode resistance, auxin transport, and gibberellin response. These 12 genes were used to build models for prediction of CIS using multiple linear regression. Nine linear models were constructed that used different combinations of the 12 genes. An F-box protein, cellulose synthase, and a putative Lax auxin transporter gene were most frequently used. The findings of this study demonstrate the utility of gene expression profiles in predictive diagnostics for severity of CIS.

Responses of dietary ileal amino acid digestibility to consumption of different cultivars of potatoes and conventional fibers in grower pigs fed a high-fat basal diet.

Whereas dietary fibers are well recognized for nutritional management of human health issues, fiber is also known to be one of the dietary factors potentially affecting digestive use of dietary proteins. As a staple food, potato (Solanum tuberosum) may be a significant dietary fiber source. The objective of this study was to examine effects of dietary supplementation of six potato cultivar-genotype samples that differ in soluble fiber content and two conventional fiber components (i.e., cellulose and guar gum) on the apparent ileal AA digestibility in pigs fed a high-fat basal diet. The basal diet was formulated as a zero-fiber negative control (NC) to contain 41.5% poultry meal, 4% casein, 15% animal fat-oil blend, 2.8% sucrose, 31% corn (Zea mays) starch, 0.50% salt, and 0.40% trace mineral-vitamin supplement with fat contributing to 47% of the dietary GE. The two fiber diets were formulated by respectively diluting the basal diet with 10% guar gum and 10% cellulose at the expense of corn starch. Six other test diets were formulated by including 8.5% guar gum and further diluting the basal diet with 25.1% one of the six cultivar-genotype samples of dehydrated potato tuber powder to contain about 10% total dietary fiber at the expense of corn starch. Eighty-one 25-kg barrows were fitted with a simple T-cannula at the distal ileum and fed the diets according to a completely randomized block design with each block lasting 28 d. Compared with the NC, the ileal digestibility of Ala, Gly, and Pro were decreased (P < 0.05) by 10% guar gum whereas the digestibility of Gly was reduced (P < 0.05) by 10% cellulose. The ileal digestibility of several AA was decreased (P < 0.05) by the test potatoes plus 8.5% guar gum compared with the NC. Our results suggest that dietary inclusion of fiber at 10% from guar gum and cellulose and contributed by potatoes may adversely affect digestive use of dietary protein.