Low Temperature-Sensitive Genes in Sweet Potatoes (Ipomoea batatas (L.) Lam.) and Their Expression Patterns during Storage

Abstract

　This study shows several genes in sweet potatoes, whose expression level changed during low-temperature storage. In addition, the relationship between their expression and occurrence of chilling injury was investigated. The expression levels of phenylalanine ammonia-lyase A (PALA), ACC oxidase, regulatory protein NPR1, 70 kDa heat shock protein, and α-amylase were increased upon storage at 5-10 ℃; however those of β-amylase (BAM) and starch synthase were decreased. The effects of continuous changes in storage temperatures on the expression of PALA and BAM were investigated. The changes in their expression levels during storage at 5 ℃ within 10 days could be recovered by storage at 20 ℃ for 5 days; however, at 5 ℃ for more than 15 days, the recovery phenomenon was not observed. PALA expression level increased at below 10 ℃, but was absent at over 13 ℃. Heat shock treatment at 40 ℃ for 2 days did not affect the expression levels of these genes. These findings indicate the irreversible physiological changes in sweet potatoes according to by low-temperature storage periods and can be used as expression makers of chilling injury.