Generation of ESTs from grape berry at various developmental stages

Expressed sequence tags (ESTs) are a main tool in functional genomics. In this paper, we report the construction of 3 unidirectional cDNA libraries from green, softening, and ripening grape berries. For each library, a set of 100 randomly selected clones were sequenced at their 3′ end. Two hundred seventy-five expressed sequence tags (ESTs) were thus generated, representing around 187,000 bp of independent cDNA. 78 % of clones demonstrated significant homology to previously deposited nucleotide and/or polypeptide sequences. Transcripts homologous to proteins with known or putative functions were classified into functional categories. Highly represented protein classes were cell wall proteins, ribosomal proteins, proteins involved in signal transduction, and ripening-related proteins. A significant proportion of the ESTs (12 %) demonstrated no significant homology to any deposited sequence. This proportion of novel plant genes was highest (19 %) at véraison, the transient period when the berry softens and irreversibly switches from an organic acid to a sugar-accumulating organ. Expression analysis of these ESTs will define the range of genes involved in the development of grape berry as a model of fleshy, acidic, phenols-rich, and non-climacteric fruit.