The cucumber mosaic virus (CMV) 2b viral suppressor of RNA silencing (VSR) is a potent counter-defense and pathogenicity factor that inhibits antiviral silencing by titration of short double-stranded RNAs. It also disrupts microRNA-mediated regulation of host gene expression by binding ARGONAUTE 1 (AGO1). But in Arabidopsis thaliana complete inhibition of AGO1 is counterproductive to CMV since this triggers another layer of antiviral silencing mediated by AGO2, de-represses strong resistance against aphids (the insect vectors of CMV), and exacerbates symptoms. Using confocal laser scanning microscopy, bimolecular fluorescence complementation, and co-immunoprecipitation assays we found that the CMV 1a protein, a component of the viral replicase complex, regulates the 2b-AGO1 interaction. By binding 2b protein molecules and sequestering them in P-bodies, the 1a protein limits the proportion of 2b protein molecules available to bind AGO1, which ameliorates 2b-induced disease symptoms, and moderates induction of resistance to CMV and to its aphid vector. However, the 1a protein-2b protein interaction does not inhibit the ability of the 2b protein to inhibit silencing of reporter gene expression in agroinfiltration assays. The interaction between the CMV 1a and 2b proteins represents a novel regulatory system in which specific functions of a VSR are selectively modulated by another viral protein. The finding also provides a mechanism that explains how CMV, and possibly other viruses, modulates symptom induction and manipulates host-vector interactions.

BackgroundMale sterility is an important mechanism for the production of hybrid seeds in watermelon. Although fruit development has been studied extensively in watermelon, there are no reports on gene expression in floral organs. In this study, RNA-sequencing (RNA-seq) was performed in two near-isogenic watermelon lines (genic male sterile [GMS] line, DAH3615-MS and male fertile line, DAH3615) to identify the differentially expressed genes (DEGs) related to male sterility.ResultsDEG analysis showed that 1259 genes were significantly associated with male sterility at a FDR P-value of < 0.01. Most of these genes were only expressed in the male fertile line. In addition, 11 functional clusters were identified using DAVID functional classification analysis. Of detected genes in RNA-seq analysis, 19 were successfully validated by qRT-PCR.ConclusionsIn this study, we carried out a comprehensive floral transcriptome sequence comparison of a male fertile line and its near-isogenic male sterile line in watermelon. This analysis revealed essential genes responsible for stamen development, including pollen development and pollen tube elongation, and allowed their functional classification. These results provided new information on global mechanisms related to male sterility in watermelon.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2186-9) contains supplementary material, which is available to authorized users.

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Karuppanapandian, T., Rhee, S.-J., Kim, E.-J., Han, B. K., Hoekenga, O. A. and Lee, G. P. 2012. Proteomic analysis of differentially expressed proteins in the roots of Columbia-0 and Landsberg erecta ecotypes of Arabidopsis thaliana in response to aluminum-toxicity. Can. J. Plant Sci. 92: 1267–1282. Aluminum (Al) is phytotoxic when solubilized into Al3+ in acidic soils and represents a major constraint for crop production. The present study describes Al-stress responses in roots of Al-tolerant and Al-sensitive Arabidopsis ecotypes, Columbia-0 (Col-0) and Landsberg erecta (Ler), respectively. Comparative proteomic analysis was applied to plants grown in hydroponic solution culture under acidic pH (4.2) conditions. To investigate time-dependent responses, 6-d-old seedlings were treated with 30 µM AlCl3 for 24, 48, or 72 h; total proteins were prepared from roots and separated by two-dimensional gel electrophoresis (2-DE). From 2-DE analysis, were 600 proteins were inspected, 29 proteins were differentially responsive to Al-treatment. The 2-DE patterns were compared and differentially expressed proteins identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Analysis of protein expression patterns revealed that a set of proteins is functionally associated with tricarboxylic acid (TCA) cycle and glycolysis, reactive oxygen quenching and detoxification mechanism, and signal transduction pathways, etc., could play important roles in mediating plant response to Al in Arabidopsis ecotypes. Comparison of the changes in the protein profiles revealed that Al-stress increased Al-tolerance related proteins in Al-tolerant Col-0, but only generic stress responses occurred in Al-sensitive Ler. Specifically, Al up-regulated proteins such as alcohol dehydrogenase, monodehydroascorbate reductase, GTP-binding nuclear protein Ran-2, and leucine aminopeptidase in Col-0 but not in Ler.