Polyploidy has been a common process during the evolution of eukaryotes, especially plants, leading to speciation and the evolution of new gene functions. Gene expression levels and patterns can change, and gene silencing can occur in allopolyploids-phenomena sometimes referred to as "transcriptome shock." Alternative splicing (AS) creates multiple mature mRNAs from a single type of precursor mRNA. Here we examined the evolution of AS patterns after polyploidy, with natural and two resynthesized allotetraploid Brassica napus lines, using RT-PCR and sequencing assays of 82 AS events in duplicated gene pairs (homeologs). Comparing the AS patterns between the two homeologs in natural B. napus revealed that many of the gene pairs show different AS patterns, with a few showing variation that was organ specific or induced by abiotic stress treatments. In the resynthesized allotetraploids, 26-30% of the duplicated genes showed changes in AS compared with the parents, including many cases of AS event loss after polyploidy. Parallel losses of many AS events after allopolyploidy were detected in the two independently resynthesized lines. More changes occurred in parallel between the two lines than changes specific to each line. The PASTICCINO gene showed partitioning of two AS events between the two homeologs in the resynthesized allopolyploids. AS changes after allopolyploidy were much more common than homeolog silencing. Our findings indicate that AS patterns can change rapidly after polyploidy, that many genes are affected, and that AS changes are an important component of the transcriptome shock experienced by new allopolyploids.gene duplication | whole genome duplication | molecular evolution P olyploidy is ubiquitous in plants, with many plants being evolutionarily recent polyploids, and all angiosperms having one or more ancient polyploidy events in their lineage (1-3). Polyploids can display novel phenotypes that may contribute to their evolutionary success (4). Gene expression levels and patterns in natural and synthetic polyploids have been widely studied to investigate the immediate and long-term effects of polyploidy. Some of the phenomena revealed include nonadditive patterns of gene expression in polyploids compared with their progenitors, divergence in expression levels and patterns between the homeologs, and gene silencing, with the effects being variable in different organ types, in different developmental stages, and in response to abiotic stresses (reviewed in refs. 5-8).Alternative splicing (AS) is a posttranscriptional mechanism that can regulate gene expression. AS also allows multiple proteins to be produced from the same gene. In addition, AS can cause transcript degradation by including premature stop codons within the coding region that target the transcripts for nonsensemediated decay, and potentially lower levels of gene expression (9, 10). Premature stop codons introduced by AS can sometimes result in truncated proteins that are functional (11). AS can result in phenotypic changes and impact m...

The INSTI HIV-1/HIV-2 Antibody Test is shown to detect anti-HIV-1 IgM antibodies in early HIV infection which enhances its utility in early HIV diagnosis.

Many tumors contain mutations that confer defects in the DNA-damage response and genome stability. DNA-damaging agents are powerful therapeutic tools that can differentially kill cells with an impaired DNA-damage response. The response to DNA damage is complex and composed of a network of coordinated pathways, often with a degree of redundancy. Tumor-specific somatic mutations in DNA-damage response genes could be exploited by inhibiting the function of a second gene product to increase the sensitivity of tumor cells to a sublethal concentration of a DNA-damaging therapeutic agent, resulting in a class of conditional synthetic lethality we call synthetic cytotoxicity. We used the Saccharomyces cerevisiae nonessential gene-deletion collection to screen for synthetic cytotoxic interactions with camptothecin, a topoisomerase I inhibitor, and a null mutation in TEL1, the S. cerevisiae ortholog of the mammalian tumor-suppressor gene, ATM. We found and validated 14 synthetic cytotoxic interactions that define at least five epistasis groups. One class of synthetic cytotoxic interaction was due to telomere defects. We also found that at least one synthetic cytotoxic interaction was conserved in Caenorhabditis elegans. We have demonstrated that synthetic cytotoxicity could be a useful strategy for expanding the sensitivity of certain tumors to DNA-damaging therapeutics.

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