Identification of putative stage-specific grapevine berry biomarkers and omics data integration into networks.

The analysis of grapevine (Vitis vinifera) berries at the transcriptomic, proteomic, and metabolomic levels can provide great insight into the molecular events underlying berry development and postharvest drying (withering). However, the large and very different data sets produced by such investigations are difficult to integrate. Here, we report the identification of putative stage-specific biomarkers for berry development and withering and, to our knowledge, the first integrated systems-level study of these processes. Transcriptomic, proteomic, and metabolomic data were integrated using two different strategies, one hypothesis free and the other hypothesis driven. A multistep hypothesis-free approach was applied to data from four developmental stages and three withering intervals, with integration achieved using a hierarchical clustering strategy based on the multivariate bidirectional orthogonal projections to latent structures technique. This identified stage-specific functional networks of linked transcripts, proteins, and metabolites, providing important insights into the key molecular processes that determine the quality characteristics of wine. The hypothesis-driven approach was used to integrate data from three withering intervals, starting with subdata sets of transcripts, proteins, and metabolites. We identified transcripts and proteins that were modulated during withering as well as specific classes of metabolites that accumulated at the same time and used these to select subdata sets of variables. The multivariate bidirectional orthogonal projections to latent structures technique was then used to integrate the subdata sets, identifying variables representing selected molecular processes that take place specifically during berry withering. The impact of this holistic approach on our knowledge of grapevine berry development and withering is discussed.

Correction: High throughput approaches reveal splicing of primary microRNA transcripts and tissue specific expression of mature microRNAs in Vitis vinifera.

UNLABELLED: The version of this article published in BMC Genomics 2009, 10:558, contains data in Table 1 which are now known to be unreliable, and an illustration, in Figure 1, of unusual miRNA processing events predicted by these unreliable data. In this full-length correction, new data replace those found to be unreliable, leading to a more straightforward interpretation without altering the principle conclusions of the study. Table 1 and associated methods have been corrected, Figure 1 deleted, supplementary file 1 added, and modifications made to the sections "Deep sequencing of small RNAs from grapevine leaf tissue" and "Microarray analysis of miRNA expression". The editors and authors regret the inconvenience caused to readers by premature publication of the original paper. BACKGROUND: MicroRNAs are short (~21 base) single stranded RNAs that, in plants, are generally coded by specific genes and cleaved specifically from hairpin precursors. MicroRNAs are critical for the regulation of multiple developmental, stress related and other physiological processes in plants. The recent annotation of the genome of the grapevine (Vitis vinifera L.) allowed the identification of many putative conserved microRNA precursors, grouped into multiple gene families. RESULTS: Here we use oligonucleotide arrays to provide the first indication that many of these microRNAs show differential expression patterns between tissues and during the maturation of fruit in the grapevine. Furthermore we demonstrate that whole transcriptome sequencing and deep-sequencing of small RNA fractions can be used both to identify which microRNA precursors are expressed in different tissues and to estimate genomic coordinates and patterns of splicing and alternative splicing for many primary miRNA transcripts. CONCLUSIONS: Our results show that many microRNAs are differentially expressed in different tissues and during fruit maturation in the grapevine. Furthermore, the demonstration that whole transcriptome sequencing can be used to identify candidate splicing events and approximate primary microRNA transcript coordinates represents a significant step towards the large-scale elucidation of mechanisms regulating the expression of microRNAs at the transcriptional and post-transcriptional levels.

High throughput approaches reveal splicing of primary microRNA transcripts and tissue specific expression of mature microRNAs in Vitis vinifera.

BACKGROUND: MicroRNAs are short (approximately 21 base) single stranded RNAs that, in plants, are generally coded by specific genes and cleaved specifically from hairpin precursors. MicroRNAs are critical for the regulation of multiple developmental, stress related and other physiological processes in plants. The recent annotation of the genome of the grapevine (Vitis vinifera L.) allowed the identification of many putative conserved microRNA precursors, grouped into multiple gene families. RESULTS: Here we use oligonucleotide arrays to provide the first indication that many of these microRNAs show differential expression patterns between tissues and during the maturation of fruit in the grapevine. Furthermore we demonstrate that whole transcriptome sequencing and deep-sequencing of small RNA fractions can be used both to identify which microRNA precursors are expressed in different tissues and to estimate genomic coordinates and patterns of splicing and alternative splicing for many primary miRNA transcripts. CONCLUSION: Our results show that many microRNAs are differentially expressed in different tissues and during fruit maturation in the grapevine. Furthermore, the demonstration that whole transcriptome sequencing can be used to identify candidate splicing events and approximate primary microRNA transcript coordinates represents a significant step towards the large-scale elucidation of mechanisms regulating the expression of microRNAs at the transcriptional and post-transcriptional levels.

Addressing drought tolerance in maize by transcriptional profiling and mapping.

In order to unravel the genetic architecture underlying plant response to drought, we adopted an integrated approach, combining transcript profiling and quantitative trait loci (QTL) mapping. In fact, improving plant tolerance to water stress is an important, but, at the same time, a difficult task, since plant tolerance is the result of many complex mechanisms acting at different levels of plant organization, and its genetic basis is largely unknown. The phenotypic data, concerning yield components and flowering time, of a population of 142 maize Recombinant Inbred Lines (RILs), grown under well watered conditions or under water stress, were submitted to linkage analysis to detect drought-tolerance QTLs. Thirty genomic regions containing 50 significant QTLs distributed on nine chromosomes were identified. At the same time, a customized targeted oligoarray was used to monitor the expression levels of 1,000 genes, representative of the immature maize kernel transcriptome. Using this DNA array we compared transcripts from 10 days after pollination kernels of two susceptible and two drought tolerant genotypes (extracted from our RILs) grown under control and water stress field conditions. Two hundred and fifty-two genes were significantly affected by stress in at least one genotype. From a set of these, 49 new molecular markers were developed. By mapping most of them and by in silico mapping other regulated sequences, 88 differentially expressed genes were localized onto our linkage map, which, added to the existing 186 markers, brought their total number on the map to 274. Twenty-two of the 88 differentially expressed genes mapped in the same chromosomal segments harbouring QTLs for tolerance, thus representing candidate genes for further functional studies.

The grapevine genome sequence suggests ancestral hexaploidization in major angiosperm phyla.

The analysis of the first plant genomes provided unexpected evidence for genome duplication events in species that had previously been considered as true diploids on the basis of their genetics. These polyploidization events may have had important consequences in plant evolution, in particular for species radiation and adaptation and for the modulation of functional capacities. Here we report a high-quality draft of the genome sequence of grapevine (Vitis vinifera) obtained from a highly homozygous genotype. The draft sequence of the grapevine genome is the fourth one produced so far for flowering plants, the second for a woody species and the first for a fruit crop (cultivated for both fruit and beverage). Grapevine was selected because of its important place in the cultural heritage of humanity beginning during the Neolithic period. Several large expansions of gene families with roles in aromatic features are observed. The grapevine genome has not undergone recent genome duplication, thus enabling the discovery of ancestral traits and features of the genetic organization of flowering plants. This analysis reveals the contribution of three ancestral genomes to the grapevine haploid content. This ancestral arrangement is common to many dicotyledonous plants but is absent from the genome of rice, which is a monocotyledon. Furthermore, we explain the chronology of previously described whole-genome duplication events in the evolution of flowering plants.

The role of barren stalk1 in the architecture of maize.

The architecture of higher plants is established through the activity of lateral meristems--small groups of stem cells formed during vegetative and reproductive development. Lateral meristems generate branches and inflorescence structures, which define the overall form of a plant, and are largely responsible for the evolution of different plant architectures. Here, we report the isolation of the barren stalk1 gene, which encodes a non-canonical basic helix-loop-helix protein required for the initiation of all aerial lateral meristems in maize. barren stalk1 represents one of the earliest genes involved in the patterning of maize inflorescences, and, together with the teosinte branched1 gene, it regulates vegetative lateral meristem development. The architecture of maize has been a major target of selection for early agriculturalists and modern farmers, because it influences harvesting, breeding strategies and mechanization. By sampling nucleotide diversity in the barren stalk1 region, we show that two haplotypes entered the maize gene pool from its wild progenitor, teosinte, and that only one was incorporated throughout modern inbreds, suggesting that barren stalk1 was selected for agronomic purposes.