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.
