The Role Of Dna Barcoding As A Tool In Molecular Systematics

ABSTRACT

Global warming is affecting regional climate, ecosystem and diversity array of species by causing physical and biological changes throughout the planet. Therefore, there is a need to develop a technique which can identify organisms and differentiate between very closely related species in order conserve species diversity. Classical taxonomy has accelerated its progress with the adoption of new molecular techniques like DNA barcoding to cope with the huge population of organisms and biodiversity available in this planet. DNA barcoding uses short gene sequences which are well classified portion of the genome. With the advent of high throughput sequencing technology such as Next-Generation Sequencing (NGS) technology the DNA barcoding has become more accurate, fast and reliable in the last decade. The Consortium for the Barcode of Life (CBOL) has given a platform for taxonomists across all the countries to collaborate, identify and preserve the biodiversity across the globe. In this review we summarized the recent advances and developments in the DNA barcoding attempts across animals, plants, bacteria, fungi, viruses and protists. We have also attempted to present the popular tools used in DNA barcoding in a chronological order of their development

CHAPTER ONE

1.0 INTRODUCTION

A DNA barcode is one or few relatively short gene sequences present in the genome which is unique enough to identify species. DNA barcoding is a useful tool for taxonomic classification and identification of species by sequencing a very short standardized DNA sequence in a well-defined gene. In this technique, complete information of the species can be obtained from a single specimen irrespective to morphological or life stage characters. It is an effective technique in which extracted DNA from the collected sample is processed following the standard protocol. Identification of the species is carried out by amplifying highly variable region i.e., DNA barcode region of the nuclear, chloroplast or mitochondrial genome using Polymerase Chain Reaction (PCR). Region widely used for DNA barcoding include nuclear DNA (e.g. ITS), chloroplast DNA (e.g. rbcL, trnL-F, matK, psbA, trnH, psbK) and mitochondrial DNA (e.g. COI). DNA barcodes can be used as a tool for grouping unknown species based on barcode sequence to earlier known species or new species. It can also be used for grouping specimens to known species in those cases where morphologic features are missing or misleading. It can also be used as a supplement to other taxonomic datasets in the process of delimiting species boundaries (Schindel and Miller, 2005). The set of DNA barcode markers have been applied to specific taxonomic groups of organisms and are proving invaluable for understanding species boundaries, community ecology, functional trait evolution, trophic interactions and the conservation of biodiversity (Lahaye et al., 2008). The application of NGS technology had expanded the versatility of DNA barcodes across the ‘Tree of Life’, habitats and geographies as new methodologies are explored and developed (Shokralla et al., 2014).

In order to characterize species, CBOL has selected few genes as ideal for DNA barcoding. Ideally, one gene sequence would be used to identify species in all of the taxa (taxonomic groups) from viruses to plants and animals. However, that ideal gene has not yet been found, so different barcode DNA sequences are used for animals, plants, microbes and viruses. Research using cytochrome c oxidase barcoding techniques on zoological specimens was initiated by Hebert and his group. From 2004, CBOL started to promote the use of a standardized DNA barcoding approach, consisting of identifying a specimen based on a single universal marker i.e., the DNA barcode sequence. An ideal DNA barcode region or locus should have low intra-specific and high inter-specific divergence (creating a “barcode gap”) and easy to amplify from most or all species in the target group using universal primers. Reference barcodes must be derived from expertly identified vouchers deposited in biological collections with online metadata and validated by available online sequence chromatograms (Hebert et al., 2003).

In this research review, the role of DNA barcoding as a tool in molecular systematic is uncovered.

Pages:  41

Category: Seminar

Format:  Word & PDF        

Chapters: 1-5

Material contains Table of Content, Abstract and References.