TRANSCRIPTOME STUDY INFERRING DIFFERENT METABOLISMS IN DEVELOPING STORAGE ROOTS OF LOW- AND HIGH-CYANIDE CONTAINING CASSAVA VARIETIES

Low-cyanide containing (sweet) cassava varieties have a growing demand in food industries, especially for functional food market such as gluten-free flour.  In contrast to the demand, cassava root production of the sweet cassava varieties is always low, not only from their growth characteristics but also being susceptible to the prevailing stresses.  Here, transcriptome analysis was conducted to decipher the biological molecular mechanism involving in storage root (SR) initiation of sweet cassava cultivars. The early developing SR (~ 40 days after planting (DAP)) of Hanatee (HN), a low-cyanide variety was examined with respect to Kasetsart 50 (KU50), a high-cyanide variety.  The results of RNA-seq data analysis were 48 differentially expressed genes (DEGs) with up-regulated in KU50 and 97 DEGs with up-regulated in HN.  Based on pathway enrichment analysis of DEGs, MAPK signaling pathway, nitrogen metabolism, plant hormone signal transduction and plant-pathogen interaction were dominant in HN, while metabolic functions of KU50 related to 2-oxocarboxylic acid metabolism, alpha-linolenic acid metabolism, ascorbate and aldarate metabolism, cyanoamino acid metabolism, diterpenoid biosynthesis, fructose and mannose metabolism, glucosinolate biosynthesis, linoleic acid metabolism. These suggested the prominent of secondary metabolite metabolisms in KU50 at SR initiation which supported SR formation.  The proposed metabolic processes and related genes may be useful for further investigation in their transcriptional regulation leading to yield improvement of sweet cassava varieties.