Development Of Functional Markers Research Articles

Comparative analysis of sequences of mitochondrial genomes of wild abortive male sterile (WA-CMS) and male fertile lines of rice, development of functional markers for WA-CMS trait and their use in assessment of genetic purity of seeds of WA-CMS lines

WA-CMS system based rice hybrids are widely adopted in many rice growing countries, including India. Even though it is well known that the trait is controlled by mitochondria, the genes underpinning the trait remain enigmatic. In the present study, a complete genome-wide comparative sequence analysis was performed using draft mitochondrial genomes of WA-CMS and male fertile lines in a step-wise manner, progressively covering 5–10 kb every time through BLASTN tool. The sequence polymorphisms identified in different mitochondrial regions were targeted to develop two different sets of dominant PCR-based markers, one consisting of six markers targeting WA-CMS mitochondria, the other set consisting of five markers targeting male fertile mitochondria in addition to development of a set of eight co-dominant PCR-based markers targeting both the genomes. When a set of candidate genes/ORFs reported earlier to be associated with WA-CMS trait in rice were analyzed through RT-PCR of RNA isolated from immature rice florets, it was observed that the chimeric ORF, WA352 is expressed only in WA-CMS line and hybrid (i.e. genotypes containing sterile mitochondria), indicating it’s candidacy for the WA-CMS trait. Targeting the functional nucleotide polymorphism between WA-CMS and maintainer mitochondria with respect to WA352, two dominant markers, one targeting sterile and another targeting fertile mitochondria were developed. In addition, a robust, co-dominant functional marker targeting the candidate gene was also developed and validated for its utility in identification of genetic impurities in seed lots of WA-CMS lines.

Stress-Induced Accumulation of DcAOX1 and DcAOX2a Transcripts Coincides with Critical Time Point for Structural Biomass Prediction in Carrot Primary Cultures (Daucus carota L.).

Stress-adaptive cell plasticity in target tissues and cells for plant biomass growth is important for yield stability. In vitro systems with reproducible cell plasticity can help to identify relevant metabolic and molecular events during early cell reprogramming. In carrot, regulation of the central root meristem is a critical target for yield-determining secondary growth. Calorespirometry, a tool previously identified as promising for predictive growth phenotyping has been applied to measure the respiration rate in carrot meristem. In a carrot primary culture system (PCS), this tool allowed identifying an early peak related with structural biomass formation during lag phase of growth, around the 4th day of culture. In the present study, we report a dynamic and correlated expression of carrot AOX genes (DcAOX1 and DcAOX2a) during PCS lag phase and during exponential growth. Both genes showed an increase in transcript levels until 36 h after explant inoculation, and a subsequent down-regulation, before the initiation of exponential growth. In PCS growing at two different temperatures (21°C and 28°C), DcAOX1 was also found to be more expressed in the highest temperature. DcAOX genes’ were further explored in a plant pot experiment in response to chilling, which confirmed the early AOX transcript increase prior to the induction of a specific anti-freezing gene. Our findings point to DcAOX1 and DcAOX2a as being reasonable candidates for functional marker development related to early cell reprogramming. While the genomic sequence of DcAOX2a was previously described, we characterize here the complete genomic sequence of DcAOX1.

Development of Functional Markers and Identification of Haplotypes for Rice Grain Shape Gene GW8

Development of Functional Markers and Identification of Haplotypes for Rice Grain Shape Gene <i>GW8</i>

Development and validation of functional CAPS markers for the FAE genes in Brassica juncea and their use in marker-assisted selection.

Low erucic acid is a major breeding target to improve the edible oil quality in Brassica juncea. The single nucleotide polymorphism (SNP) in fatty acid elongase 1 (FAE1.1 and FAE1.2) gene was exploited to expedite the breeding program. The paralogs of FAE1 gene were sequenced from low erucic acid genotype Pusa Mustard 30 and SNPs were identified through homologous alignment with sequence downloaded from NCBI GenBank. Two SNPs in FAE1.1 at position 591 and 1265 and one in FAE1.2 at 237 were found polymorphic among low and high erucic acid genotypes. These SNPs either create or change the recognition site of restriction enzymes. Transition of a single nucleotide at position 591 and 1265 in FAE1.1, and at position 237 in FAE1.2, leads to a change in the recognition site of Hpy99I, BglII and MnlI restriction enzymes, respectively. Two CAPS markers for FAE1.1 and one for FAE1.2 were developed to differentiate low and high erucic acid genotypes. The efficiency of these CAPS markers was found 100 per cent when validated in Brassica juncea, and B. nigra genotypes and used in back-cross breeding. These CAPS markers will facilitate in marker-assisted selection for improvement of oil quality in Brassica juncea.

Identification of Genes Responsible for Natural Variation in Volatile Content Using Next-Generation Sequencing Technology.

Identification of the genes controlling the variation of key traits remains a challenge for plant researchers and represents a goal for the development of functional markers and their implementation in marker-assisted crop breeding. As an example we describe the identification of volatile organic compounds (VOCs) that segregate as single locus or mayor quantitative trait loci (QTL) in strawberry F1 segregating populations. Next, we describe a fast and efficient method for RNA extraction in strawberry that yields high-quality RNA for downstream RNA-seq analysis. Finally, two alternative methods for analysis of global transcript expression in contrasting lines will be described in order to identify the candidate gene and genes with differential expression using RNA-seq.

Parallel consideration of SSRs and differentially expressed genes under abiotic stress for targeted development of functional markers in almond and related Prunus species

RNA-Seq approach is widely used to study plant transcriptome responses to different environmental stresses. RNA-Seq datasets have also become valuable resources to develop SSR markers and other types of markers in plant species. However, there are challenges such as the validation of SSR polymorphisms, and translation of these information into a functional approach for plant breeding programs. In our recent work, the first de novo transcriptome assembly of almond have been reported in response to freezing stress, and thousands of differential expression (DE) genes have been identified. Here, for the first time, we have suggested a parallel consideration of genes with DE under frost stress and SSR markers to find functional markers in almond (Prunus dulcis Mill.) and other related Prunus species. The term “RNA-Seq SSR” was used in the current study, replacing the previous term “EST-SSR” (expressed sequence tagged), for the distinction between traditional EST sequencing and the new RNA-Seq methods. Eleven RNA-Seq SSR markers were identified as polymorphic markers. Some of SSR loci were found on genes which are responsive in cold and other abiotic stresses, including calmodulin, trihelix transcription factor GT-1-like and delta-(8)-fatty-acid desaturase. Furthermore, these markers revealed high polymorphism in population of Prunus arabica, Prunus scoparia and Prunus haussknechtii. Our overall results suggest potential application of DE genes carrying SSR sequences as functional markers. The developed workflow and the new findings presented here are likely to open new opportunity for future genetic diversity, association studies and breeding projects of almond and other plants grown under environmental stresses. This workflow can also be applied to targeted validation and development of SNP and/or indel markers.

De novo assembly and characterization of foot transcriptome and microsatellite marker development for Paphia textile

Paphia textile is an important, aquaculture bivalve clam species distributed mainly in China, Philippines, and Malaysia. Recent studies of P. textile have focused mainly on artificial breeding and nutrition analysis, and the transcriptome and genome of P. textile have rarely been reported. In this work, the transcriptome of P. textile foot tissue was sequenced on an Illumina HiSeq™ 2000 platform. A total of 20,219,795 reads were generated, resulting in 4.08Gb of raw data. The raw reads were cleaned and assembled into 54,852 unigenes with an N50 length of 829bp. Of these unigenes, 38.92% were successfully annotated based on their matches to sequences in seven public databases. Among the annotated unigenes, 14,571 were assigned Gene Ontology terms, 5448 were classified to Clusters of Orthologous Groups categories, and 6738 were mapped to 228 pathways in the Kyoto Encyclopedia of Genes and Genomes database. For functional marker development, 5605 candidate simple sequence repeats were identified in the transcriptome and 80 primer pairs were selected randomly and amplified in a wild population of P. textile. A total of 36 loci that exhibited obvious repeat length polymorphisms were detected. The transcriptomic data and microsatellite markers will provide valuable resources for future functional gene analyses, genetic map construction, and quantitative trait loci mapping in P. textile.

Degenerate Oligonucleotide Primed–Polymerase Chain Reaction‐Based Chromosome Painting of P Genome Chromosomes in Agropyron cristatum and Wheat–A. cristatum Addition Lines

ABSTRACTAgropyron cristatum (L.) Gaertn. (2n = 4x = 28, PPPP), a wild relative of wheat, could provide many desirable genes for wheat improvement. Microdissection and degenerate oligonucleotide primed –polymerase chain reaction (DOP–PCR) is an effective way to isolate specific sequences. The development of specific sequences and functional markers of P genome could lay the foundation for gene mapping and cloning. In this study, chromosomes 6PS and 6PL were microdissected from wheat–A. cristatum 6PS and 6PL addition lines, and DOP–PCR products from both microdissected chromosomes were used as probes to hybridize with mitotic metaphase chromosomes of diploid A. cristatum, wheat–A. cristatum addition lines 6PS, 6PL, and 6P. The results showed that the distribution patterns on A. cristatum chromosomes using DOP–PCR products of microdissected 6PS as the probe were similar to those using DOP–PCR products of microdissected 6PL as the probe. They both distributed along all chromosomes, and chromosome 6P and other chromosomes were similar according to the hybridization pattern. There were no signals on wheat chromosomes indicating that DOP–PCR products contain P‐genome specific sequences. Actually, we obtained a P‐genome specific sequence from the DOP–PCR products of 6PS, which could be used as a fluoresence in situ hybridization (FISH) probe to identify P genome chromatin in wheat–A. cristatum introgression lines. These results could provide a basis for the study of structure and evolution of P genome chromosomes. Furthermore, this study may lead to mapping and cloning of the desirable genes on 6P chromosome.

Discovery of a novel fragrant allele and development of functional markers for fragrance in rice

Fragrance in rice (Oryza sativa L.) results from the loss of function of the betaine aldehyde dehydrogenase (Badh2) gene on chromosome 8. An 8-bp deletion in exon 7 of Badh2 was reported to be the main allele functionally associated with fragrance. The discovery of new functional alleles will provide additional genetic resources to improve fragrant rice. In this study, we sequenced the Badh2 gene in 30 rice accessions and filtered the Badh2 polymorphisms from whole-genome re-sequence data of 295 rice accessions. Seven alleles were detected from the sequence data. Six of the seven were known alleles and one was a novel allele (badh2-E12). The novel allele was a 3-bp deletion in exon 12. Five functional markers, targeting six of the seven alleles, were identified. Fourteen accessions were selected to test the utility of these markers. The five molecular markers reliably distinguish this fragrant rice from other fragrant or non-fragrant rice accessions. Analysis of two F2 rice population validated the genetic markers FME12-3 and FME14I as functional markers. These two markers co-segregated with the fragrance phenotype. These markers will be used in a Badh2 diversity study and to breed improved fragrant rice accessions via marker-assisted selection.

A comprehensive meta-analysis of plant morphology, yield, stay-green, and virus disease resistance QTL in maize (Zea mays L.).

The meta-QTL and candidate genes will facilitate the elucidation of molecular bases underlying agriculturally important traits and open new avenues for functional markers development and elite alleles introgression in maize breeding program. A large number of QTLs attributed to grain productivity and other agriculturally important traits have been identified and deposited in public repositories. The integration of fruitful QTL becomes a major issue in current plant genomics. To this end, we first collected QTL for six agriculturally important traits in maize, including yield, plant height, ear height, leaf angle, stay-green, and maize rough dwarf disease resistance. The meta-analysis method was then employed to retrieve 113 meta-QTL. Additionally, we also isolated candidate genes for target traits by the bioinformatic technique. Several candidates, including some well-characterized genes, GA3ox2 for plant height, lg1 and lg4 for leaf angle, zfl1 and zfl2 for flowering time, were co-localized with established meta-QTL intervals. Intriguingly, in a relatively narrow meta-QTL region, the maize ortholog of rice yield-related gene GW8/OsSPL16 was believed to be a candidate for yield. Leveraging results presented in this study will provide further insights into the genetic architecture of maize agronomic traits. Moreover, the meta-QTL and candidate genes reported here could be harnessed for the enhancement of stress tolerance and yield performance in maize and translation to other crops.

Review of functional markers for improving cooking, eating, and the nutritional qualities of rice.

After yield, quality is one of the most important aspects of rice breeding. Preference for rice quality varies among cultures and regions; therefore, rice breeders have to tailor the quality according to the preferences of local consumers. Rice quality assessment requires routine chemical analysis procedures. The advancement of molecular marker technology has revolutionized the strategy in breeding programs. The availability of rice genome sequences and the use of forward and reverse genetics approaches facilitate gene discovery and the deciphering of gene functions. A well-characterized gene is the basis for the development of functional markers, which play an important role in plant genotyping and, in particular, marker-assisted breeding. In addition, functional markers offer advantages that counteract the limitations of random DNA markers. Some functional markers have been applied in marker-assisted breeding programs and have successfully improved rice quality to meet local consumers’ preferences. Although functional markers offer a plethora of advantages over random genetic markers, the development and application of functional markers should be conducted with care. The decreasing cost of sequencing will enable more functional markers for rice quality improvement to be developed, and application of these markers in rice quality breeding programs is highly anticipated.

Genome-wide association for grain yield under rainfed conditions in historical wheat cultivars from Pakistan.

Genome-wide association studies (GWAS) were undertaken to identify SNP markers associated with yield and yield-related traits in 123 Pakistani historical wheat cultivars evaluated during 2011–2014 seasons under rainfed field conditions. The population was genotyped by using high-density Illumina iSelect 90K single nucleotide polymorphism (SNP) assay, and finally 14,960 high quality SNPs were used in GWAS. Population structure examined using 1000 unlinked markers identified seven subpopulations (K = 7) that were representative of different breeding programs in Pakistan, in addition to local landraces. Forty four stable marker-trait associations (MTAs) with -log p > 4 were identified for nine yield-related traits. Nine multi-trait MTAs were found on chromosomes 1AL, 1BS, 2AL, 2BS, 2BL, 4BL, 5BL, 6AL, and 6BL, and those on 5BL and 6AL were stable across two seasons. Gene annotation and syntey identified that 14 trait-associated SNPs were linked to genes having significant importance in plant development. Favorable alleles for days to heading (DH), plant height (PH), thousand grain weight (TGW), and grain yield (GY) showed minor additive effects and their frequencies were slightly higher in cultivars released after 2000. However, no selection pressure on any favorable allele was identified. These genomic regions identified have historically contributed to achieve yield gains from 2.63 million tons in 1947 to 25.7 million tons in 2015. Future breeding strategies can be devised to initiate marker assisted breeding to accumulate these favorable alleles of SNPs associated with yield-related traits to increase grain yield. Additionally, in silico identification of 454-contigs corresponding to MTAs will facilitate fine mapping and subsequent cloning of candidate genes and functional marker development.

De novo transcriptome assembly and analysis of Sf21 cells using illumina paired end sequencing.

Spodoptera is an important polyphagous agricultural insect pest in the tropical world. The genomic details are limited to understand the pest biology at molecular level. In the present study, we sequenced and assembled the transcriptome from Sf21 cells into a non redundant set of 24,038 contigs of ~ 47.38 Mb in size. A total of 26,390 unigenes were identified from the assembled transcripts and their annotation revealed the prevalent protein domains in Sf21 cells. The present study would provide a resource for gene discovery and development of functional molecular markers to understand the biology of S. frugiperda.ReviewersThis article was reviewed by Dr. Thiago Motta Venancio and Prof. Michael Gray.Electronic supplementary materialThe online version of this article (doi:10.1186/s13062-015-0072-7) contains supplementary material, which is available to authorized users.

Functional marker development of miR1511-InDel and allelic diversity within the genus Glycine.

BackgroundSingle-stranded non-protein coding small RNAs, 18–25 nucleotides in length, are ubiquitous throughout plants genomes and are involved in post-transcriptional gene regulation. Several types of DNA markers have been reported for the detection of genetic diversity or sequence variation in soybean, one of the most important legume crops in worldwide for seed protein and oil content. Recently, with the available of public genomic databases, there has been a shift from the labor-intensive development of PCR-based markers to sequence-based genotyping and the development of functional markers within genes, often coupled with the use of RNA information. But thus far miRNA-based markers have been only developed in rice and tobacco. Here we report the first functional molecular miRNA marker, miR1511-InDel, in soybean for a specific single copy locus used to assess genetic variation in domesticated soybean (Glycine max [L.] Merr) and its wild progenitor (Glycine soja Sieb. & Zucc.).ResultsWe genotyped a total of 1,669 accessions of domesticated soybean (G. max) and its wild progenitor G. soja which are native throughout the China and parts of Korea, Japan and Russia. The results indicate that the miR1511 locus is distributed in cultivated soybean and has three alleles in annual wild soybean. Based on this result, we proposed that miR-InDel marker technology can be used to assess genetic variation. The inclusion of geo-reference data with miR1511-InDel marker data corroborated that accessions from the Yellow River basin (Huanghuai) exhibited high genetic diversity which provides more molecular evidence for gene diversity in annual wild soybean and domestication of soybean.ConclusionsThese results provide evidence for the use of RNA marker, miRNA1511-InDel, as a soybean-specific functional maker for the study of genetic diversity, genotyping of germplasm and evolution studies. This is also the first report of functional marker developed from soybean miRNA located within the functional region of pre-miRNA1511.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1665-3) contains supplementary material, which is available to authorized users.

Development and validation of SNP-based functional codominant markers for two major disease resistance genes in rice (O. sativa L.)

Blast and bacterial leaf blight are major diseases of rice that limit grain yield significantly. These two devastating biotic stresses have to be controlled to meet the demand for 23 % more rice production by 2035 to feed the increasing number of rice consumers. Incorporating appropriate disease resistance genes into elite varieties is considered as the best method to enhance crop resistance. Molecular markers play an important role in multiple gene pyramiding programs to select desirable genotypes with targeted genes. Two major resistance genes, Pita and xa5, for blast and bacterial leaf blight races, respectively, have been used in many gene pyramiding programs. However, simple PCR-based functional codominant markers have not been reported for these genes. Hence, in the present study, time- and cost-effective codominant markers for Pita and xa5 have been developed and validated in segregating populations. High-throughput screening has been demonstrated using parallel capillary electrophoresis to replace laborious gel-based electrophoresis. Additionally, the presence of Pita and xa5 alleles was evaluated with 260 diverse rice varieties that were collected from different parts of the world. Of the 260 cultivars tested, 55 were identified with the Pita resistance allele while all the tested cultivars had the susceptible Xa5 allele. The identified Pita allele-derived cultivars can be used as an alternative resistance source for blast disease. The newly developed Pita and xa5 functional markers will help toward tracking the two target genes for blast and bacterial leaf blight resistance in breeding programs.

Development and Characterization of Transcription Factor Gene-Derived Microsatellite (TFGM) Markers in Medicago truncatula and Their Transferability in Leguminous and Non-Leguminous Species.

Transcription factors (TFs) are critical adaptor molecules that regulate many plant processes by controlling gene expression. The recent increase in the availability of TF data has made TFs a valuable resource for genic functional microsatellite marker development. In the present study, we developed TF gene-derived microsatellite (TFGM) markers for Medicago truncatula and assessed their cross-species transferability. A total of 203 SSRs were identified from 1467 M. truncatula TF coding sequences, 87.68% of which were trinucleotide repeats, followed by mono- (4.93%) and hexanucleotide repeats (1.48%). Further, 142 TFGM markers showed a high level of transferability to the leguminous (55.63%–85.21%) and non-leguminous (28.17%–50.00%) species. Polymorphisms of 27 TFGM markers were evaluated in 44 alfalfa accessions. The allele number per marker ranged from two to eight with an average of 4.41, and the PIC values ranged from 0.08 to 0.84 with an average of 0.60. Considering the high polymorphism, these TFGM markers developed in our study will be valuable for genetic relationship assessments, marker-assisted selection and comparative genomic studies in leguminous and non-leguminous species.

Molecular characterization of Fom-1 gene and development of functional markers for molecular breeding of resistance to Fusarium race 2 in melon

Melon Fusarium wilt disease caused by the soil-borne pathogen Fusarium oxysporum f. sp. melonis (Fom) is one of the most devastating melon diseases worldwide. Recently, the Fom-1 gene responsible for resistance against Fom races 0 and 2 was cloned. In this study we amplified, cloned and sequenced full genomic DNA and cDNA of Fom-1 from several melon resistant and susceptible accessions using three pairs of primers designed within this gene. Sequence analyses showed that this gene contains four exons interrupted by three introns. The comparative sequence analysis of the cloned cDNA amplicons from resistant and susceptible genotypes revealed eight nucleotide substitutions, within Fom-1 coding regions, among which four were non-synonymous. RT-PCR revealed that the Fom-1 expression is induced by Fom race 2 inoculation. The Fom-1 predicted protein (FOM-1) exhibits a tripartite modular structure composed of an N-terminal TIR domain, a central NB–ARC domain and a C-terminal LRR domain. FOM-1 from resistant melon accessions share four amino acid differences relative to the FOM-1 protein in susceptible ones. Two amino acid substitutions N56K and R103H were located at the FOM-1 TIR domain and the substitution E385K in the NB–ARC domain. Based on single nucleotide polymorphisms within the coding region of the Fom-1 locus, we have generated two CAPS markers, Fom-1R and Fom-1S. Results from screening various melon accessions clearly demonstrated the usefulness of both functional CAPS markers in the marker-assisted selection for melon breeding programs.

USE OF DIGITAL GENE EXPRESSION TO DISCRIMINATE GENE EXPRESSION IN DIFFERENT DEVELOPMENTAL STAGES OF ROSA CHINENSIS 'PALLIDA'

Rosa chinensis ‘Pallida’ (Rosa L.) is one of the most important ancient rose cultivars originating in China. It contributed the ‘tea scent’ trait to modern roses. However, very little information available on the gene regulatory networks was involved in scent biosynthesis and metabolism in Rosa. In this study, digital gene expression (DGE) profiling was used to measure the gene expression in flower bud, bloom and senescent development stages. A total of 16,223 transcripts exhibited significant expression change among the three libraries. KEGG pathways analysis showed that specific enrichment of genes was observed for pathways involved in phenylpropanoid and terpenoid backbone biosynthesis in the three developmental stages. Five transcripts encoding putative proteins related to scent synthesis were identified and their expressions were validated using qRT-PCR. The study provides the foundation for scent-related gene discovery and development of functional molecular markers in roses.

Functional marker development is challenged by the ubiquity of endophytes-a practical perspective.

Functional markers (FMs) are supposed to assist in diagnosis, disease treatment and turning plant and animal breeding more efficient. However, efficient FM application is challenged through current insights in the multi-organism nature of life. This letter aims to raise awareness for re-thinking concepts for FM development in plant breeding and proposes a novel perspective.

De novo assembly of the common bean transcriptome using short reads for the discovery of drought-responsive genes.

The common bean (Phaseolus vulgaris L.) is one of the most important food legumes, far ahead of other legumes. The average grain yield of the common bean worldwide is much lower than its potential yields, primarily due to drought in the field. However, the gene network that mediates plant responses to drought stress remains largely unknown in this species. The major goals of our study are to identify a large scale of genes involved in drought stress using RNA-seq. First, we assembled 270 million high-quality trimmed reads into a non-redundant set of 62,828 unigenes, representing approximately 49 Mb of unique transcriptome sequences. Of these unigenes, 26,501 (42.2%) common bean unigenes had significant similarity with unigenes/predicted proteins from other legumes or sequenced plants. All unigenes were functionally annotated within the GO, COG and KEGG pathways. The strategy for de novo assembly of transcriptome data generated here will be useful in other legume plant transcriptome studies. Second, we identified 10,482 SSRs and 4,099 SNPs in transcripts. The large number of genetic markers provides a resource for gene discovery and development of functional molecular markers. Finally, we found differential expression genes (DEGs) between terminal drought and optimal irrigation treatments and between the two different genotypes Long 22-0579 (drought tolerant) and Naihua (drought sensitive). DEGs were confirmed by quantitative real-time PCR assays, which indicated that these genes are functionally associated with the drought-stress response. These resources will be helpful for basic and applied research for genome analysis and crop drought resistance improvement in the common bean.