A single degenerated primer significantly improves COX1 barcoding performance in soil nematode community profiling

A new COX1 primer for soil nematode metabarcoding was designed,and this primer outperforms other commonly used COX1 primer pairs in species recovery and quantity of PCR products.•The lack of reference database is the main reason that led to the low species recovery in COX1 metabarcoding.•We expanded current NCBI database by adding 51 newly generated COX1 reference sequences.Microscopic nematodes play important roles in soil ecosystems and often serve as bioindicators of soil health.The identification of soil nematodes is often difficult due to their limited diagnostic characters and high phenotypic plasticity.DNA barcoding and metabarcoding techniques are promising but lack universal primers,especially for mitochondrial COX1 gene.In this study a degenerated COX1 forward primer COIFGED was developed.The primer pair(COIFGED/JB5GED)outperforms other four commonly used COX1 primer pairs in species recovery and quantity of polymerase chain reaction(PCR)products.In metabarcoding analysis,the reads obtained from the new primer pair had the highest sequencing saturation threshold and amplicon sequence variant(ASV)diversity in comparison to other COX1 as well as 18S rRNA primers.The annotation of ASVs suggested the new primer pair initially recovered 9 and 6 out of 25 genera from mock communities,respectively,outperformed other COX1 primers,but underperformed the widely used 18S NF1/18Sr2b primers(16 out of 25 genera).By supplementing the COX1 database with our reference sequences,we recovered an additional 6 mock community species bringing the tally closer to that obtained with 18S primers.In summary,our newly designed COX1 primers significantly improved species recovery and thus can be supplementary or alternative to the conventional 18S metabarcoding.

DNA sequencing by synthesis with degenerate primers

The degenerate primer-based sequencing was developed by a synthesis method （DP-SBS） for high-throughput DNA sequencing, in which a set of degenerate primers are hybridized on the arrayed DNA templates and extended by DNA polymerase on microarrays. In this method, a different set of degenerate primers containing a given number （n） of degenerate nucleotides at the 3＇-ends were annealed to the sequenced templates that were immobilized on the solid surface. The nucleotides （n＋1） on the template sequences were determined by detecting the incorporation of fluorescent labeled nucleotides. The fluorescent labeled nucleotide was incorporated into the primer in a base-specific manner after the enzymatic primer extension reactions and nine-base length were read out accurately. The main advantage of the DP-SBS is that the method only uses very conventional biochemical reagents and avoids the complicated special chemical reagents for removing the labeled nucleotides and reactivating the primer for further extension. From the present study, it is found that the DP-SBS method is reliable, simple, and cost-effective for laboratory-sequencing a large amount of short DNA fragments.

Molecular Characterization of the Duck Enteritis Virus UL4 Gene

Duck enteritis virus(DEV) is a herpesvirus that causes an acute,contagious and fatal disease. In the present article,the DEV UL4 gene was cloned and sequenced from a vaccine virus. A degenerate oligonucleotide primer for the consensus site of herpesvirus UL3 gene and a specific primer located in UL5 were used in the polymerase chain reaction(PCR) to amplify a DNA product 2 086 bp in size. DNA sequence analysis revealed that a 714 bp open reading frame(ORF) of DEV encoding a 237 amino acid polypeptide is homologous to the family of herpesvirus UL4 proteins and therefore has been characterized as a DEV UL4 gene. Alignment of the DEV UL4 protein sequence with those of other alphaherpesviruses showed that 10 amino acid residues are completely conserved. Phylogenetic tree analysis showed that the seventeen alphaherpesviruses viruses analyzed were classified into four large groups,and the duck enteritis virus branched separately,closely related to the Mardiviruses group comprising Gallid herpesvirus 2(GaHV-2) ,Gallid herpesvirus 3(GaHV-3) and Meleagrid herpesvirus 1(MeHV-1) . The present study showed that the evolutionary relationship of the UL4 protein could be used for classification of alphaherpesviruses.

Cloning of Na^+/H^+ antiport gene from Dunaliella salina

1 Introduction Dunaliella Salina,which taxi Dunaliella,Volvocales,Chlorophyceae Chlorophyta,is unicell algae with double flagllum at top,and cup shaped chloroplast without cell wall.Dunaliella Salina is the most salt tolerance eucaryotes.It can grow at the range of salt concentration

Streamlined whole-genome genotyping through NGS-enhanced thermal asymmetric interlaced(TAIL)-PCR

Whole-genome genotyping(WGG)stands as a pivotal element in genomic-assisted plant breeding.Nevertheless,sequencing-based approaches for WGG continue to be costly,primarily owing to the high expenses associated with library preparation and the laborious protocol.During prior development of foreground and background integrated genotyping by sequencing(FBI-seq),we discovered that any sequence-specific primer(SP)inherently possesses the capability to amplify a massive array of stable and reproducible non-specific PCR products across the genome.Here,we further improved FBI-seq by replacing the adapter ligated by Tn5 transposase with an arbitrary degenerate(AD)primer.The protocol for the enhanced FBI-seq unexpectedly mirrors a simplified thermal asymmetric interlaced(TAIL)-PCR,a technique that is widely used for isolation of flanking sequences.However,the improved TAIL-PCR maximizes the primer-template mismatched annealing capabilities of both SP and AD primers.In addition,leveraging of next-generation sequencing enhances the ability of this technique to assay tens of thousands of genome-wide loci for any species.This cost-effective,user-friendly,and powerful WGG tool,which we have named TAIL-PCR by sequencing(TAIL-peq),holds great potential for widespread application in breeding programs,thereby facilitating genome-assisted crop improvement.

Identification and initial characterization of the 3＇ end of gene transcripts encoding putative members of the pheromone receptor subfamily in Lepidoptera

Semiochemicals, including pheromones and kairomones, used in pest man- agement programs reduce the need for chemical insecticides, and understanding their interactions with their membrane receptors may help make them more effective in the field. Identification of odorant receptors in the Lepidoptera has mainly been achieved us- ing bioinformatics to search DNA sequences generated by genome or expressed sequence tag （EST） sequencing projects. This study reports a rapid method to identify members of the pheromone receptor subfamily in Lepidoptera. Degenerate oligonucleotide primers were designed against a conserved amino acid sequence in the carboxyl terminus of known lepidopteran pheromone receptors, and the primers were used in a 3＇ rapid amplifica- tion of complementary DNA （cDNA） ends procedure. Polymerase chain reaction products generated from seven different lepidopteran species were TA cloned and sequenced. The cDNA sequences of 25 transcripts were determined to encode potential members of the pheromone receptor subfamily. These cDNAs ranged from 238 to 642 bp and encoded 49-54 amino acids of the carboxyl terminus. Analysis of the 3＇ untranslated region reveals that most of the transcripts contain multiple polyadenylation signal sequences, and in the case ofManduca sexta, an alternate polyadenylation signal appears to be used in transcript processing. The 3＇ untranslated region was also useful in determining unique receptors en- coded by transcripts having highly similar nucleotide and amino acid sequences. Overall, this technique provides a complementary method of pheromone receptor identification in EST sequencing projects, or can be used as a stand-alone method in conjunction with 5＇ rapid amplification of cDNA ends procedures.