Transcriptome profiling of Chironomus kiinensis under phenol stress using Solexa sequencing technology.

Phenol is a major pollutant in aquatic ecosystems due to its chemical stability, water solubility and environmental mobility. To date, little is known about the molecular modifications of invertebrates under phenol stress. In the present study, we used Solexa sequencing technology to investigate the transcriptome and differentially expressed genes (DEGs) of midges (Chironomus kiinensis) in response to phenol stress. A total of 51,518,972 and 51,150,832 clean reads in the phenol-treated and control libraries, respectively, were obtained and assembled into 51,014 non-redundant (Nr) consensus sequences. A total of 6,032 unigenes were classified by Gene Ontology (GO), and 18,366 unigenes were categorized into 238 Kyoto Encyclopedia of Genes and Genomes (KEGG) categories. These genes included representatives from almost all functional categories. A total of 10,724 differentially expressed genes (P value <0.05) were detected in a comparative analysis of the expression profiles between phenol-treated and control C. kiinensis including 8,390 upregulated and 2,334 downregulated genes. The expression levels of 20 differentially expressed genes were confirmed by real-time RT-PCR, and the trends in gene expression that were observed matched the Solexa expression profiles, although the magnitude of the variations was different. Through pathway enrichment analysis, significantly enriched pathways were identified for the DEGs, including metabolic pathways, aryl hydrocarbon receptor (AhR), pancreatic secretion and neuroactive ligand-receptor interaction pathways, which may be associated with the phenol responses of C. kiinensis. Using Solexa sequencing technology, we identified several groups of key candidate genes as well as important biological pathways involved in the molecular modifications of chironomids under phenol stress

ECHIDNA protein impacts on male fertility in Arabidopsis by mediating trans-Golgi network secretory trafficking during anther and pollen development

The trans-Golgi network (TGN) plays a central role in cellular secretion and has been implicated in sorting cargo destined for the plasma membrane. Previously, the Arabidopsis (Arabidopsis thaliana) echidna (ech) mutant was shown to exhibit a dwarf phenotype due to impaired cell expansion. However, ech also has a previously uncharacterized phenotype of reduced male fertility. This semisterility is due to decreased anther size and reduced amounts of pollen but also to decreased pollen viability, impaired anther opening, and pollen tube growth. An ECH translational fusion (ECHPro:ECH-YELLOW FLUORESCENT PROTEIN) revealed developmentally regulated tissue-specific expression, with expression in the tapetum during early anther development and microspore release and subsequent expression in the pollen, pollen tube, and stylar tissues. Pollen viability and production, along with germination and pollen tube growth, were all impaired. The ech anther endothecium secondary wall thickening also appeared reduced and disorganized, resulting in incomplete anther opening. This did not appear to be due to anther secondary thickening regulatory genes but perhaps to altered secretion of wall materials through the TGN as a consequence of the absence of the ECH protein. ECH expression is critical for a variety of aspects of male reproduction, including the production of functional pollen grains, their effective release, germination, and tube formation. These stages of pollen development are fundamentally influenced by TGN trafficking of hormones and wall components. Overall, this suggests that the fertility defect is multifaceted, with the TGN trafficking playing a significant role in the process of both pollen formation and subsequent fertilization

Comparison of gene expression level between the two libraries.

<p>For comparing gene expression level between the two libraries, each library was normalized to 1 million tags. Red dots represent transcripts more prevalent in the phenol treatment library, green dots show those present at a lower frequency in the infected tissue and blue dots indicate transcripts that did not change significantly. The parameters “FDR<0.001” and “log2 Ratio≥1” were used as the threshold to judge the significance of gene expression difference.</p

Length distribution of non-redundant consensus sequences.

*<p>N50 = median length of all unigenes; **Mean size = average length of all unigenesGO and COG classification</p

Summary for the <i>Chironomus kiiensis</i> transcriptome in phenol treated (PT) and control (CK) libraries.

<p>Summary for the <i>Chironomus kiiensis</i> transcriptome in phenol treated (PT) and control (CK) libraries.</p

Primers used in Real-time RT-PCR.

<p>Primers used in Real-time RT-PCR.</p

Differentially expressed genes in phenol tissue library.

<p>The “X” axis represents fold-change of DEGs in the PT library. The “y” axis represents the number of unique tags (log 10).</p

GO annotations of non-redundant consensus sequences.

<p>Best hits were aligned to the GO database, and 6032 transcripts were assigned to at least one GO term. Most consensus sequences were grouped into three major functional categories, namely biological process, cellular component, and molecular function.</p