Molecular analysis of differentially expressed genes during postharvest deterioration in cassava (Manihot esculenta Crantz) tuberous roots

One of the major problems for cassava is the rapid deterioration after harv esting cassava tuberous roots, which limits the possibilities for productio n and distribution of cassava in the world. Postharvest deterioration is an inherent problem for cassava since wounding and mechanical damage of the t uberous roots cannot be prevented during harvesting, which includes posthar vest physiological deterioration (PPD) and secondary deterioration. To date , the molecular mechanism and biochemical pathways of PPD are poorly unders tood. The aim of this project, which is focusing on the early stages (first 72 hrs), is to gain molecular insight and identify important metabolic pat hways during the process of PPD in cassava tuberous roots. Finally by rever se genetic approaches to delay or even prevent the process of PPD in cassav a tuberous roots. By using a new RNA fingerprinting method, called cDNA-AFL P, we have screened more than 6,000 TDFs (Transcript Derived Fragments) via up to 100 primer combinations during the early process of PPD in cassava. Only 10% of the TDFs are developmentally regulated, while the other 90% are expressed throughout the process of PPD in cassava tuberous roots. Further more, in order to set up a functional catalogue of differentially expressed genes during PPD, 70 TDFs were selected and isolated based on their expres sion patterns, which were either up-regulated, down-regulated or transientl y induced. Around 40 of these TDFs were found to be similar with known gene s in databases. The other 30 TDFs were present mostly genes without known f unction. Through data analysis, it is shown that important biochemical and physiological processes, such as notably oxygen stress, carbohydrate metabo lism, protein metabolism and phenolic compounds synthesis, are involved in PPD in cassava tuberous roots.