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The increasing amount of available expressed gene sequence data makes whole-transcriptome analysis of certain crop species possible. Potato currently has the second largest number of publicly available expressed sequence tag (EST) sequences among the Solanaceae. Most of these ESTs, plus other proprietary sequences, were combined and used to generate a unigene assembly. The set of 246,182 sequences produced 46,345 unigenes, which were used to design a 44K 60-mer oligo array (Potato Oligo Chip Initiative: POCI). In this study, we attempt to identify genes controlling and driving the process of tuber initiation and growth by implementing large-scale transcriptional changes using the newly developed POCI array. Major gene expression profiles could be identified exhibiting differential expression at key developmental stages. These profiles were associated with functional roles in cell division and growth. A subset of genes involved in the regulation of the cell cycle, based on their Gene Ontology classification, exhibit a clear transient upregulation at tuber onset indicating increased cell division during these stages. The POCI array allows the study of potato gene expression on a much broader level than previously possible and will greatly enhance analysis of transcriptional control mechanisms in a wide range of potato research areas. POCI sequence and annotation data are publicly available through the POCI database ( http://pgrc.ipk-gatersleben.de/poci ).

In alfalfa nodules induced by Rhizobium meliloti strain L5-30 the compound L-3- O -methyl- scyllo -inosamine (3- O -M S I) is synthesized. This compound is also catabolized specifically by this strain. Its biological properties are therefore similar to the Agrobacterium opines. To answer the question whether opine-like compounds (“Rhizopines”) play a role in a plant symbiotic interaction, we isolated the genes for the catabolism of 3- O -M S I ( moc genes) and for the induction of its synthesis in the nodule [ mos gene(s)]. moc and mos genes were shown to be closely linked and located on the Sym plasmid of L5-30, suggesting that they have co-evolved and may be important in symbiosis. These genes have been cloned into a broad host-range vector that can be mobilized into other R. meliloti strains where they are expressed. The location of the mos genes in the bacteria extends the opine concept, initially developed for a plant pathological interaction, to a symbiotic one.