Annotation and validation of genes involved in photosynthesis and starch synthesis from a Manihot full-length cDNA library

Abstract

A full-length cDNA library from leaf and root tissues of cassava (Manihot esculenta) Arg7 and one accession of its wild ancestor W14 (M. esculenta ssp. flabellifolia) has been constructed. The library is comprised of four sub-libraries, containing 32640 recombinant clones, 6028 cDNA clones from their 5′ ends, and 128 clones from the 3′ ends were sequenced. In total, 5013 high-quality expressed sequence tags (ESTs) and 1259 unigenes were obtained. Of these, 746 unigenes were identified by their sequence homologies to ESTs from model plants, and 323 unigenes were mapped onto 114 different KEGG pathways. From these, 24 differentially expressed genes involved in starch metabolism and photosynthesis were identified and five of them were selected to compare their expression level between Arg7 and W14. Notably, Arg7 has a higher net photosynthesis rate in leaves, higher ribulose-1,5-bisphosphate carboxy-lase oxygenase activities in leaves, and higher AGPase activity in roots. This resource is the first EST collection from wild cassava and should be of value for gene discovery, genome annotation and studies of Manihot evolution