Expression Profiling of Cassava Storage Roots Reveals an Active Process of Glycolysis/GluconeogenesisF

Abstract

Mechanisms related to the development of cassava storage roots and starch accumulation remain largely unknown. To evaluate genome‐wide expression patterns during tuberization, a 60 mer oligonucleotide microarray representing 20 840 cassava genes was designed to identify differentially expressed transcripts in fibrous roots, developing storage roots and mature storage roots. Using a random variance model and the traditional twofold change method for statistical analysis, 912 and 3 386 upregulated and downregulated genes related to the three developmental phases were identified. Among 25 significantly changed pathways identified, glycolysis/gluconeogenesis was the most evident one. Rate‐limiting enzymes were identified from each individual pathway, for example, enolase, L‐lactate dehydrogenase and aldehyde dehydrogenase for glycolysis/gluconeogenesis, and ADP‐glucose pyrophosphorylase, starch branching enzyme and glucan phosphorylase for sucrose and starch metabolism. This study revealed that dynamic changes in at least 16% of the total transcripts, including transcription factors, oxidoreductases/transferases/hydrolases, hormone‐related genes, and effectors of homeostasis. The reliability of these differentially expressed genes was verified by quantitative real‐time reverse transcription‐polymerase chain reaction. These studies should facilitate our understanding of the storage root formation and cassava improvement.