The complete mitochondrial genome of the citrus red mite Panonychus citri (Acari: Tetranychidae): high genome rearrangement and extremely truncated tRNAs

<p>Abstract</p> <p>Background</p> <p>The family Tetranychidae (Chelicerata: Acari) includes ~1200 species, many of which are of agronomic importance. To date, mitochondrial genomes of only two Tetranychidae species have been sequenced, and it has been found that these two mitochondrial genomes are characterized by many unusual features in genome organization and structure such as gene order and nucleotide frequency. The scarcity of available sequence data has greatly impeded evolutionary studies in Acari (mites and ticks). Information on Tetranychidae mitochondrial genomes is quite important for phylogenetic evaluation and population genetics, as well as the molecular evolution of functional genes such as acaricide-resistance genes. In this study, we sequenced the complete mitochondrial genome of <it>Panonychus citri </it>(Family Tetranychidae), a worldwide citrus pest, and provide a comparison to other Acari.</p> <p>Results</p> <p>The mitochondrial genome of <it>P. citri </it>is a typical circular molecule of 13,077 bp, and contains the complete set of 37 genes that are usually found in metazoans. This is the smallest mitochondrial genome within all sequenced Acari and other Chelicerata, primarily due to the significant size reduction of protein coding genes (PCGs), a large rRNA gene, and the A + T-rich region. The mitochondrial gene order for <it>P. citri </it>is the same as those for <it>P. ulmi </it>and <it>Tetranychus urticae</it>, but distinctly different from other Acari by a series of gene translocations and/or inversions. The majority of the <it>P. citri </it>mitochondrial genome has a high A + T content (85.28%), which is also reflected by AT-rich codons being used more frequently, but exhibits a positive GC-skew (0.03). The Acari mitochondrial <it>nad1 </it>exhibits a faster amino acid substitution rate than other genes, and the variation of nucleotide substitution patterns of PCGs is significantly correlated with the G + C content. Most tRNA genes of <it>P. citri </it>are extremely truncated and atypical (44-65, 54.1 ± 4.1 bp), lacking either the T- or D-arm, as found in <it>P. ulmi</it>, <it>T. urticae</it>, and other Acariform mites.</p> <p>Conclusions</p> <p>The <it>P. citri </it>mitochondrial gene order is markedly different from those of other chelicerates, but is conserved within the family Tetranychidae indicating that high rearrangements have occurred after Tetranychidae diverged from other Acari. Comparative analyses suggest that the genome size, gene order, gene content, codon usage, and base composition are strongly variable among Acari mitochondrial genomes. While extremely small and unusual tRNA genes seem to be common for Acariform mites, further experimental evidence is needed.</p

A GDSL-motif esterase/acyltransferase/lipase is responsible for leaf water retention in barley

The hydrophobic cuticle covers the surface of the most aerial organs of land plants. The barley mutant eceriferum‐zv (cer‐zv), which is hypersensitive to drought, is unable to accumulate a sufficient quantity of cutin in its leaf cuticle. The mutated locus has been mapped to a 0.02 cM segment in the pericentromeric region of chromosome 4H. As a map‐based cloning approach to isolate the gene was therefore considered unlikely to be feasible, a comparison was instead made between the transcriptomes of the mutant and the wild type. In conjunction with extant genomic information, on the basis of predicted functionality, only two genes were considered likely to encode a product associated with cutin formation. When eight independent cer‐zv mutant alleles were resequenced with respect to the two candidate genes, it was confirmed that the gene underlying the mutation in each allele encodes a Gly‐Asp‐Ser‐Leu (GDSL)‐motif esterase/acyltransferase/lipase. The gene was transcribed in the epidermis, and its product was exclusively deposited in cell wall at the boundary of the cuticle in the leaf elongation zone, coinciding with the major site of cutin deposition. CER‐ZV is speculated to function in the deposition of cutin polymer. Its homologs were found in green algae, moss, and euphyllophytes, indicating that it is highly conserved in plant kingdom

Aminopolysiloxane as Cu2O Photocathode Overlayer: Photocorrosion Inhibitor and Low Overpotential CO2-to-formate Selectivity Promoter

Cu2O, a photoactive p-type semiconductor based on earth-abundant elements, shows promising features for photoelectrochemical CO2 reduction reaction (PEC CO2RR). However, despite the broad light absorption and appropriate conduction band edge energy, it promptly undergoes photocorrosion in PEC CO2RR conditions. Herein, we evaluate an amine-functionalized polysiloxane (AF−PSi) as both protective layer and PEC CO2RR promoter via amine-CO2 adduct formation. Electrochemistry experiments and X-ray diffraction showed that photostability is significantly enhanced with AF−PSi overlayer. Electrolyses experiments under visible light irradiation indicated selective production of formate with faradaic efficiency of 61 % at low overpotential. Detailed in situ FTIR studies revealed that amine groups bind to CO2 to form carbamate species and that this process is favoured by cathodic polarization, confirming the dual role of AF−PSi layer

Evolution of the grain dispersal system in barley

Published: July 30, 2015About 12,000 years ago in the Near East, humans began the transition from hunter-gathering to agriculture-based societies. Barley was a founder crop in this process, and the most important steps in its domestication were mutations in two adjacent, dominant, and complementary genes, through which grains were retained on the inflorescence at maturity, enabling effective harvesting. Independent recessive mutations in each of these genes caused cell wall thickening in a highly specific grain "disarticulation zone," converting the brittle floral axis (the rachis) of the wild-type into a tough, non-brittle form that promoted grain retention. By tracing the evolutionary history of allelic variation in both genes, we conclude that spatially and temporally independent selections of germplasm with a non-brittle rachis were made during the domestication of barley by farmers in the southern and northern regions of the Levant, actions that made a major contribution to the emergence of early agrarian societies.Mohammad Pourkheirandish, Goetz Hensel, Benjamin Kilian, Natesan Senthil, Guoxiong Chen, Mohammad Sameri, Perumal Azhaguvel, Shun Sakuma, Sidram Dhanagond, Rajiv Sharma, Martin Mascher, Axel Himmelbach, Sven Gottwald, Sudha K. Nair, Akemi Tagiri, Fumiko Yukuhiro, Yoshiaki Nagamura, Hiroyuki Kanamori, Takashi Matsumoto, George Willcox, Christopher P. Middleton, Thomas Wicker, Alexander Walther, Robbie Waugh, Geoffrey B. Fincher, Nils Stein, Jochen Kumlehn, Kazuhiro Sato, and Takao Komatsud