Characterization of Transcriptional Complexity during Berry Development in <i>Vitis vinifera</i> Using RNA-Seq

The development of massively parallel sequencing technologies enables the sequencing of total cDNA (RNA-Seq) to derive accurate measure of individual gene expression, differential splicing activity, and to discover novel regions of transcription, dramatically changing the way that the functional complexity of transcriptomes can be studied. Here we report on the first use of RNA-Seq to gain insight into the wide range of transcriptional responses that are associated with berry development in Vitis vinifera 'Corvina'. More than 59 million sequence reads, 36 to 44 bp in length, were generated from three developmental stages: post setting, véraison, and ripening. The sequence reads were aligned onto the 8.4-fold draft sequence of the Pinot Noir 40024 genome and then analyzed to measure gene expression levels, to detect alternative splicing events, and expressed single nucleotide polymorphisms. We detected 17,324 genes expressed during berry development, 6,695 of which were expressed in a stage-specific manner, suggesting differences in expression for genes in numerous functional categories and a significant transcriptional complexity. This exhaustive overview of gene expression dynamics demonstrates the utility of RNA-Seq for identifying single nucleotide polymorphisms and splice variants and for describing how plant transcriptomes change during development.