Topically delivered 22 nt siRNAs enhance RNAi silencing of endogenous genes in two species.

22 nt siRNAs applied to leaves induce production of transitive sRNAs for targeted genes and can enhance local silencing. Systemic silencing was only observed for a GFP transgene. RNA interference (RNAi) is a gene silencing mechanism important in regulating gene expression during plant development, response to the environment and defense.

Exogenous RNA as a Regulatory Signal during a Plant's Interaction with the Biotic Environment: An Evolutionary Perspective and Future Applications in Agriculture.

Environmental RNAi (eRNAi) is a sequence-specific regulation of endogenous gene expression in a responsive organism by exogenous RNA. While exogenous RNA transfer between organisms of different kingdoms of life have been unambiguously identified in nature, our understanding of the biological significance of this phenomenon remains obscure, particularly within an evolutionary context. During the last decade multiple reports utilizing various mechanisms of natural eRNAi phenomena have been attempted to develop new agricultural traits and products including weed, disease and insect control.

Barriers to Efficient Foliar Uptake of dsRNA and Molecular Barriers to dsRNA Activity in Plant Cells.

Foliar application of dsRNA to elicit an RNA interference (RNAi) response is currently under consideration as a crop protection strategy. To access the RNAi machinery of a plant, foliarly applied dsRNAs must traverse the plant cuticle, avoid nuclease degradation, and penetrate the cell wall and plasma membrane. Application methods and co-formulants have been identified by Bayer Crop Science researchers and others that can help bypass barriers to dsRNA uptake in plants leading to an RNAi response in greenhouse grown, young plants and cell cultures.

Water deficit modulates the response of Vitis vinifera to the Pierce's disease pathogen Xylella fastidiosa.

Pierce's disease, caused by the bacterium Xylella fastidiosa, is one of the most devastating diseases of cultivated grape, currently restricted to the Americas. To test the long-standing hypothesis that Pierce's disease results from pathogen-induced drought stress, we used the Affymetrix Vitis GeneChip to compare the transcriptional response of Vitis vinifera to Xylella infection, water deficit, or a combination of the two stresses. The results reveal a redirection of gene transcription involving 822 genes with a minimum twofold change (P < 0.

Diagnosis of Pierce's disease using biomarkers specific to Xylella fastidiosa rRNA and Vitis vinifera gene expression.

Pierce's disease (PD), caused by Xylella fastidiosa, represents one of the most damaging diseases of cultivated grape. Management of PD in the vineyard often relies on the removal of infected individuals, which otherwise serve as a source of inoculum for nearby healthy vines. Effective implementation of such control measures requires early diagnosis, which is complicated by the fact that infected vines often harbor high titers of the pathogen in advance of visual symptom development.

Impact of genetics and environment on the metabolite composition of maize grain.

This study sought to assess genetic and environmental impacts on the metabolite composition of maize grain. Gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) measured 119 identified metabolites including free amino acids, free fatty acids, sugars, organic acids, and other small molecules in a range of hybrids derived from 48 inbred lines crossed against two different tester lines (from the C103 and Iodent heterotic groups) and grown at three locations in Iowa. It was reasoned that expanded metabolite coverage would contribute to a comprehensive evaluation of the grain metabolome, its degree of variability, and, in principle, its relationship to other compositional and agronomic features.

Comparative expression profiling in grape (Vitis vinifera) berries derived from frequency analysis of ESTs and MPSS signatures.

Background: Vitis vinifera (V. vinifera) is the primary grape species cultivated for wine production, with an industry valued annually in the billions of dollars worldwide. In order to sustain and increase grape production, it is necessary to understand the genetic makeup of grape species.

Characterization and comparison of intron structure and alternative splicing between Medicago truncatula, Populus trichocarpa, Arabidopsis and rice.

Alignment of transcripts and genome sequences yielded a set of alternatively spliced transcripts in four angiosperm genomes: three dicotyledon species Medicago truncatula (Medicago), Populus trichocarpa (poplar) and Arabidopsis thaliana (Arabidopsis), and the monocotyledon Oryzae sativa (rice). Intron retention was the predominant mode of alternative splicing (AS) in each species, consistent with previous reports for Arabidopsis and rice. We analyzed the structure of 5'-splice junctions and observed commonalities between species.

Characterizing the grape transcriptome. Analysis of expressed sequence tags from multiple Vitis species and development of a compendium of gene expression during berry development.

We report the analysis and annotation of 146,075 expressed sequence tags from Vitis species. The majority of these sequences were derived from different cultivars of Vitis vinifera, comprising an estimated 25,746 unique contig and singleton sequences that survey transcription in various tissues and developmental stages and during biotic and abiotic stress. Putatively homologous proteins were identified for over 17,752 of the transcripts, with 1,962 transcripts further subdivided into one or more Gene Ontology categories.