Comparative transcriptome profiling of sweetpotato storage roots during curing-mediated wound healing

Abstract

Sweetpotato (Ipomoea batatas L. Lam) is an economically important crop that is cultivated for its storage roots. Storage roots provide a source of valuable nutrients, processed foods, animal feeds, and pigments. Sweetpotato storage roots spoil during post-harvest handling because of wounding, which makes them more susceptible to disease-causing microorganisms. Curing to promote wound healing is a common method to control microbial spoilage during post-harvest storage. However, molecular mechanisms underlying the process of curing in sweetpotato storage roots are unknown. To better understand the biology behind curing, the transcriptome of the sweetpotato cultivar, Pungwonmi, was studied using RNA-seq. Storage roots of sweetpotato were treated at 33 degrees C (Curing) and 13 degrees C (Control) for 3 days. RNA-seq data identified 78,781 unigenes and 3,366 differentially expressed genes by over log2 fold change (FC) > 2 and <-2. During curing, DEGs encoded genes related to drought/salt stress responses, phyto-hormones (e.g., auxin, ethylene and jasmonic acid), and proteolysis, were up-regulated, whereas those related to redox state, phyto-hormones (e.g., salicylic acid and brassinosteroids), and lignin and flavonoid biosynthesis were down-regulated. Additionally, among the candidate genes, DEGs encoded genes related to proteolysis and pathogen defense, such as protease inhibitors and lipid transfer proteins, were highly up-regulated during curing and storage. This study provides a valuable resource to further understand the molecular basis of curing-mediated wound healing in sweetpotato storage roots. Moreover, genes revealed in this work could present targets for the development of sweetpotato varieties with improved postharvest storage characteristics.