S. V. Kumar

Complete chloroplast genome sequence of MD-2 pineapple and its comparative analysis among nine other plants from the subclass Commelinidae

BackgroundPineapple (Ananas comosus var. comosus) is known as the king of fruits for its crown and is the third most important tropical fruit after banana and citrus. The plant, which is indigenous to South America, is the most important species in the Bromeliaceae family and is largely traded for fresh fruit consumption. Here, we report the complete chloroplast sequence of the MD-2 pineapple that was sequenced using the PacBio sequencing technology.ResultsIn this study, the high error rate of PacBio long sequence reads of A. comosus’s total genomic DNA were improved by leveraging on the high accuracy but short Illumina reads for error-correction via the latest error correction module from Novocraft. Error corrected long PacBio reads were assembled by using a single tool to produce a contig representing the pineapple chloroplast genome. The genome of 159,636xa0bp in length is featured with the conserved quadripartite structure of chloroplast containing a large single copy region (LSC) with a size of 87,482xa0bp, a small single copy region (SSC) with a size of 18,622xa0bp and two inverted repeat regions (IRA and IRB) each with the size of 26,766xa0bp. Overall, the genome contained 117 unique coding regions and 30 were repeated in the IR region with its genes contents, structure and arrangement similar to its sister taxon, Typha latifolia. A total of 35 repeats structure were detected in both the coding and non-coding regions with a majority being tandem repeats. In addition, 205 SSRs were detected in the genome with six protein-coding genes contained more than two SSRs. Comparative chloroplast genomes from the subclassxa0Commelinidae revealed a conservative protein coding gene albeit located in a highly divergence region. Analysis of selection pressure on protein-coding genes using Ka/Ks ratio showed significant positive selection exerted on the rps7 gene of the pineapple chloroplast with P less than 0.05. Phylogenetic analysis confirmed the recent taxonomical relation among the member of commelinids which support the monophyly relationship between Arecales and Dasypogonaceae and between Zingiberales to the Poales, which includes the A. comosus.ConclusionsThe complete sequence of the chloroplast of pineapple provides insights to the divergence of genic chloroplast sequences from the members of the subclass Commelinidae. The complete pineapple chloroplast will serve as a reference for in-depth taxonomical studies in the Bromeliaceae family when more species under the family are sequenced in the future. The genetic sequence information will also make feasible other molecular applications of the pineapple chloroplast for plant genetic improvement.

Development of ESTs and data mining of pineapple EST-SSRs.

Abstract:Improving the quality of the non-climacteric fruit, pineapple, is possible with information on the expression of genes that occur during the process of fruit ripening. This can be made known though the generation of partial mRNA transcript sequences known as expressed sequence tags (ESTs). ESTs are useful not only for gene discovery but also function as a resource for the identification of molecular markers, such as simple sequence repeats (SSRs). This paper reports on firstly, the construction of a normalized library of the mature green pineapple fruit and secondly, the mining of EST-SSRs markers using the newly obtained pineapple ESTs as well as publically available pineapple ESTs deposited in GenBank. Sequencing of the clones from the EST library resulted in 282 good sequences. Assembly of sequences generated 168 unique transcripts (UTs) consisting of 34 contigs and 134 singletons with an average length of ≈500xa0bp. Annotation of the UTs categorized the known proteins transcripts into the three ontologies as: molecular function (34.88%), biological process (38.43%), and cellular component (26.69%). Approximately 7% (416) of the pineapple ESTs contained SSRs with an abundance of trinucleotide SSRs (48.3%) being identified. This was followed by dinucleotide and tetranucleotide SSRs with frequency of 46 and 57%, respectively. From these EST-containing SSRs, 355 (85.3%) matched to known proteins while 133 contained flanking regions for primer design. Both the ESTs were sequenced and the mined EST-SSRs will be useful in the understanding of non-climacteric ripening and the screening of biomarkers linked to fruit quality traits.

Isolation and characterization of microsatellite loci in Phalaenopsis gigantea.

This paper describes the characterization of the population structure of an exxa0situ population of Phalaenopsis gigantea, an endangered epiphytic orchid endemic to Sabah, Malaysia, using 30 polymorphic microsatellite loci. The objective of this investigation was the estimation of the genetic distance between accessions within an exxa0situ population on the basis of which a conservation strategy aimed at selective breeding and restoration was developed.

Characterization of 10 novel microsatellite loci for the brown marbled grouper, Epinephelus fuscoguttatus (Serranidae).

Epinephelus fuscoguttatus is a commercially important marine fish species in southeast Asia. Due to overfishing and water pollution, this species has been declared as near-threatened. Thus, to provide information to help maintain and preserve the species, microsatellites were developed, using an enriched genomic library method. Thirty individuals were collected from the hatchery of the Fishery Research Institute, Terengganu, Malaysia. These individuals, from four to six years old, originated from Sabah and are maintained in captive culture as broodstock. Genomic DNA was extracted from the fins of selected individuals that weighed 3-8 kg. Ten microsatellite loci were found to be polymorphic in this population, with 5 to 21 alleles per locus. Observed and expected heterozygosities ranged from 0.53 to 0.97 and 0.59 to 0.95, respectively. Only one locus deviated significantly from Hardy-Weinberg equilibrium and no significant linkage disequilibrium was found among the pairs of loci. These polymorphic microsatellite loci will be used by the Malaysian Fishery Research Institute for investigating genetic diversity and for developing breeding strategies.

Isolation and characterization of 24 microsatellite loci in Paphiopedilum rothschildianum, an endangered slipper orchid

This paper describes the characterization of 24 polymorphic microsatellite loci in Paphiopedilum rothschildianum, an endangered slipper orchid endemic to Sabah, Malaysia. A total of 36 clones containing microsatellite repeat motifs yielded 41 dinucleotide, 20 tetranucleotide and 30 cryptic simple repeat sequences. Thirty microsatellite loci were randomly selected to characterize the population, of which 24 were found to be polymorphic. The expected heterozygosity ranged from 0.0813 to 0.7279 (mean 0.4533) and the observed heterozygosity ranged from 0 to 1 (mean 0.3800). The results indicated that there was limited migration between the three subpopulations and a significant degree of genetic differentiation (FSTxa0=xa00.5098) between populations implying that gene flow has been disrupted as a result of habitat fragmentation. The molecular markers have a potential application in population management, CITES enforcement and the forensic detection of specimens in international trade.

Lignocellulolytic Activities among Trichoderma Isolates from Lahad Datu,Sabah and Deception Island, Antarctic

Trichoderma species have the potential for application in composting as biological control agents in controlling disease and increasing yield of production in the agricultural industry. The prevalent soil fungus of Trichoderma produces lignocellulolytic enzymes that assist the degradation of woody lignocellulose materials. The aim of the experimental work was to check the potential of lignocellulolytic Trichoderma fungi for the use of rapid composting of oil palm empty fruit bunches fibers. Fifty-two of Trichoderma isolates from Sabah and seven isolates from Antarctic were examined for in-vitro lignocellulolytic activity by assaying their ability to develop dark brown pigments, yellow halo zone, and clear white zone on tannic acid media (TAM) for lignin; Jensen Media (JM) for cellulose; and modified Melin–Nokrans media (MMNM) for starch. The best six Sabah Trichoderma isolates (5D, 10L2, 10P, 5E, 10X, and 10E2) were found to be potential lignocellulolytic agents based on their diameter of halo zone formed on amended media for further testing of in vitro bioconversion of oil palm empty fruit bunches. The diameters of halo zones were measured for the analysis of their ability in degrading lignin, cellulose, and starch. In contrast, Antarctic Trichoderma isolates consistently exhibited lower lignocellulolytic activities based on their smaller diameter of halo zone formed on TAM, JM, and MMNM. Most of the Trichoderma isolates are found to synthesize polyphenol oxidase, endoglucanases, and are able to hydrolyze starch to glucose in the three different media. Thus, the finding shows the potential of these isolates for use in large-scale composting of oil palm empty fruit bunches.

Homogeneous nature of Malaysian Marine fish Epinephelus fuscoguttatus (Perciformes; Serranidae): Evidence based on molecular markers, morphology and fourier transform infrared analysis

Taxonomic confusion exists within the genus Epinephelus due to the lack of morphological specializations and the overwhelming number of species reported in several studies. The homogenous nature of the morphology has created confusion in the Malaysian Marine fish species Epinephelus fuscoguttatus and Epinephelus hexagonatus. In this study, the partial DNA sequence of the 16S gene and mitochondrial nucleotide sequences of two gene regions, Cytochrome Oxidase Subunit I and III were used to investigate the phylogenetic relationship between them. In the phylogenetic trees, E. fuscoguttatus was monophyletic with E. hexagonatus species and morphology examination shows that no significant differences were found in the morphometric features between these two taxa. This suggests that E. fuscoguttatus is not distinguishable from E. hexagonatus species, and that E. fuscoguttatus have been identified to be E. hexagonatus species is likely attributed to differences in environment and ability to camouflage themselves under certain conditions. Interestingly, this finding was also supported by Principal Component Analysis on Attenuated Total Reflectance–Fourier-transform Infrared (ATR-FTIR) data analysis. Molecular, morphological and meristic characteristics were combined with ATR-FTIR analysis used in this study offer new perspectives in fish species identification. To our knowledge, this is the first report of an extensive genetic population study of E. fuscoguttatus in Malaysia and this understanding will play an important role in informing genetic stock-specific strategies for the management and conservation of this highly valued fish.

Extensive sharing of mitochondrial COI and CYB haplotypes among reef-building staghorn corals (Acropora spp.) in Sabah, North Borneo

Abstract This study is aimed at establishing a baseline on the genetic diversity of the Acropora corals of Sabah, North Borneo based on variations in the partial COI and CYB nucleotide sequences. Comparison across 50 shallow-water Acropora morphospecies indicated that the low substitution rates in the two genes were due to negative selection and that rate heterogeneity between them was asymmetric. CYB appeared to have evolved faster than COI in the Acropora as indicated by differences in the rate of pairwise genetic distance, degrees of transition bias (Ts/Tv), synonymous-to-nonsynonymous rate ratio (dN/dS), and substitution patterns at the three codon positions. Despite the relatively high haplotype diversity (Hd), nucleotide diversity (π) of the haplotype datasets was low due to stringent purifying selection operating on the genes. Subsequently, we identified individual COI and CYB haplotypes that were each extensively shared across sympatrically and allopatrically distributed Indo-Pacific Acropora. These reciprocally common mtDNA types were suspected to be ancestral forms of the genes whereas other haplotypes have mostly evolved from autoapomorphic mutations which have not been fixed within the species even though they are selectively neutral. To our knowledge, this is the first report on DNA barcodes of Acropora species in North Borneo and this understanding will play an important role in the management and conservation of these important reef-building corals.

Genomic structure of the native inhabitants of Peninsular Malaysia and North Borneo suggests complex human population history in Southeast Asia

Southeast Asia (SEA) is enriched with a complex history of peopling. Malaysia, which is located at the crossroads of SEA, has been recognized as one of the hubs for early human migration. To unravel the genomic complexity of the native inhabitants of Malaysia, we sequenced 12 samples from 3 indigenous populations from Peninsular Malaysia and 4 native populations from North Borneo to a high coverage of 28–37×. We showed that the Negritos from Peninsular Malaysia shared a common ancestor with the East Asians, but exhibited some level of gene flow from South Asia, while the North Borneo populations exhibited closer genetic affinity towards East Asians than the Malays. The analysis of time of divergence suggested that ancestors of Negrito were the earliest settlers in the Malay Peninsula, whom first separated from the Papuans ~xa050–33 thousand years ago (kya), followed by East Asian (~xa040–15xa0kya), while the divergence time frame between North Borneo and East Asia populations predates the Austronesian expansion period implies a possible pre-Neolithic colonization. Substantial Neanderthal ancestry was confirmed in our genomes, as was observed in other East Asians. However, no significant difference was observed, in terms of the proportion of Denisovan gene flow into these native inhabitants from Malaysia. Judging from the similar amount of introgression in the Southeast Asians and East Asians, our findings suggest that the Denisovan gene flow may have occurred before the divergence of these populations and that the shared similarities are likely an ancestral component.

Molecular markers for the DNA fingerprinting of Paphiopedilum dayanum and Paphiopedilum lowii, two endangered slipper orchids

Molecular markers were developed for the DNA fingerprinting of Paphiopedilum dayanum and Paphiopedilum lowii, two endangered slipper orchids, endemic to Borneo. A total of eight and fourteen genomic loci containing putative microsatellites were converted into ten species specific molecular markers for multi-locus genetic fingerprinting of P. dayanum and P. lowii, respectively.