A Precise Stabilization Method for Linear Stochastic Time-Delay Systems

Based on ensuring the steady-state performance of the system, some dynamic performance indicators that have not yet been realized in linear stochastic systems with time-delay are discussed in this paper. First, in view of the relationship between system eigenvalues and system performances, the region stability is provided, which can reflect the dynamic performance of the systems. Second, the design scheme of the region stabilization controller is given based on the region stability, so that the closed-loop system has the corresponding dynamic performance. Third, this paper also designs an algorithm to deal with the situation in which the eigenvalues are located in the non-connected region in order to obtain more accurate control system dynamic performance. Finally, an example shows how the precise control method dominates the dynamic performance of the system

Identification of a putative polyketide synthase gene involved in usnic acid biosynthesis in the lichen Nephromopsis pallescens.

Usnic acid is a unique polyketide produced by lichens. To characterize usnic acid biosynthesis, the transcriptome of the usnic-acid-producing lichen-forming fungus Nephromopsis pallescens was sequenced using Illumina NextSeq technology. Seven complete non-reducing polyketide synthase genes and nine highly-reducing polyketide synthase genes were obtained through transcriptome analysis. Gene expression results obtained by qPCR and usnic acid detection with LCMS-IT-TOF showed that Nppks7 is probably involved in usnic acid biosynthesis in N. pallescens. Nppks7 is a non-reducing polyketide synthase with a MeT domain that also possesses beta-ketoacyl-ACP synthase, acyl transferase, product template, acyl carrier protein, C-methyltransferase, and Claisen cyclase domains. Phylogenetic analysis shows that Nppks7and other polyketide synthases from lichens form a unique monophyletic clade. Taken together, our data indicate that Nppks7 is a novel PKS in N. pallescens that is likely involved in usnic acid biosynthesis

Histogram presentation of eggNOG classification of the assembled unigenes.

<p>Histogram presentation of eggNOG classification of the assembled unigenes.</p

Known non-reducing PKSs with MeT domains and their products.

<p>The genes <i>ATEG-10080</i>, <i>ATEG-03629</i>, <i>ATEG-03432</i> and <i>ATEG-0776</i> are from <i>Aspergillus terreus</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199110#pone.0199110.ref029" target="_blank">29</a>]. Both <i>Tspks2</i> and <i>Tspks3</i> are from <i>Talaromyces stipitatus</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199110#pone.0199110.ref043" target="_blank">43</a>]. <i>PksCT</i> is from <i>Monascus purpureus</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199110#pone.0199110.ref042" target="_blank">42</a>]. <i>Cupks1</i> is from <i>Cladonia uncialis</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199110#pone.0199110.ref010" target="_blank">10</a>]. <i>Nppks6</i> and <i>Nppks7</i> are from <i>Nephromopsis pallescens</i>. 1: 3,5-dimethylorsellinic acid; 2: 5-methylorsellinic acid; 3: 6-acetyl-2,7-dihydroxy-3-methylnaphthalene-1,4-dione; 4: 2,4-dihydroxy-3-methyl-6-(2-oxopropyl)benzaldehyde; 5: 2,4-dihydroxy-6-(5,7-dimethyl-2-oxo-trans-3-trans-5-nonadienyl)-3-methylbenzaldehyde; 6: beta-orsellinic acid; 7: methylphloracetophenone. KS, beta-ketoacyl-ACP synthase; AT, acyl transferase; PT, product template domain; ACP, acyl carrier protein; MeT, C-methyltransferase; R, reductive releasing domain; TE, thioesterase domain; CLC, Claisen cyclase domain.</p

The length distribution of unigenes, the horizontal coordinates are unigene lengths and the vertical coordinates are numbers of unigenes.

<p>The length distribution of unigenes, the horizontal coordinates are unigene lengths and the vertical coordinates are numbers of unigenes.</p

Phylogenetic relationships between <i>Nephromopsis pallescens</i> polyketide synthase (PKS) genes and other fungal PKSs.

<p>The KS domain of deduced PKS proteins were aligned with fungal PKS sequences retrieved from GenBank. Sequences were aligned using Clustal W and analyzed according to the minimum evolution method. A phylogenetic tree with 1000 bootstrap replicates was generated, with a branch support threshold of 70%. PKSs from the <i>N</i>. <i>pallescens</i> clade are marked in bold.</p

Detection of usnic acid in extracts of different <i>N</i>. <i>pallescens</i> cultures.

<p>Cultures maintained on each of the following media each resulted in different extracts, respectively: MY (1.5% malt-yeast, Difco, Lawrence, USA); MYM (MY+2% mannitol); PDB (2.5% potato dextrose broth, Difco, Lawrence, USA); MS (0.5% Murashige and Skoog medium (Chembase, Shanghai, China); 5 g/L glucose); CMG (10g/L casein peptone; 5g/L maltose, 10g/L glucose); SMG (10g/L soya peptone, 5g/L maltose, 10g/L glucose); and TMG (10g/L tomato extract, 5g/L maltose, 10g/L glucose). The culture media were collected by filtration and extracted with 100 mL ethyl acetate. The crude extracts were redissolved in 2 mL of methanol. The SIM (single ion monitoring) mode of three ions, 345.0932 ([M+H]+), 709.1534 ([2M-H]-), and 343.0827 ([M-H]-) are presented as the main ions in the mass spectra for usnic acid. These three ions were used as monitoring ions in the LCMS analyses.</p