CONSERVATION OF PLANT SPECIES IN DNA BANKS
C Kameswara Rao
for Biotechnology Awareness and Education,
DNA banks or Gene banks are the ultimate facility for the ex situ conservation of genetic material to be sourced for a) genomic studies, b) to compile genomic libraries, and c) to isolate desired genes at will, for genetic engineering. However, currently they are not useful in regenerating whole plants, unlike the other forms of germplasm banking.
Any part of a plant yields DNA. Plant material is dried using silica gel and stored at -800 C to extract DNA from it. When fresh supplies not available, DNA can be obtained from dried plant material stored in botanical research institutions that house pressed and dried plant specimens called ‘herbarium’. Though some fraction of the DNA from dried plants may be degraded, it would yield quality DNA in sufficient quantities.
DNA samples in the banks pass through extensive extraction procedures, minimizing cleaning process before using the sample. However, the quality and concentration of DNA in a sample vary with species and so concentration procedures may be needed. Even small quantities of DNA are adequate as they can be amplified a million fold using the technique of ‘polymerase chain reaction’ (PCR) that yields much larger quantities of DNA from minute quantities.
Samples in DNA banks are so well purified that they are stable at ambient temperatures for days in transit. While within the bank under controlled conditions, they are stable almost indefinitely. Ten-year old DNA samples were near perfect.
DNA banking is more economical than other forms of germplasm banking, as it occupies far lesser space, almost indefinitely viable and a small sample can be shared by many researchers through PCR amplification, without the need for repetitive extractions.
The following are some important examples among several DNA banks established in different parts of the world, which are networked for collaborative activity:
The DNA Bank at the Jodrell Laboratory, Royal Botanic Gardens, Kew, England, contains over 22,000 samples of plant genomic DNA, all stored at -80°C. Information on the stored DNA is databased providing the names of the species, collectors, localities, etc. Each sample has a reference voucher of a herbarium specimen. This database is linked to the Plant DNA C-values Database and the Database of the International Plant Names Index, which is quite useful.
DNA samples are provided to the collaborators all over world but can also be purchased by the others on a Material Transfer Agreement.
The PDBK website provides genomic lists of stored DNA and tissue samples, and their voucher information (label, specimen, and photo) held in PDBK and Korea University Herbarium (KUS), both located in the Graduate School of Biotechnology, Korea University, Seoul, Korea.
The APDB located at Southern Cross University's Centre for Plant Conservation Genetics at Lismore, is a comprehensive collection of DNA from both Australian native and important crop plant species. It also contains DNA of transgenic organisms developed through genetic engineering. The APDB has invested heavily in advanced DNA storage facilities to ensure long term preservation of extracted DNA.
Although the MBG describes its activity as ‘DNA Banking’, there is no evidence on its website that MBG banks extracted DNA samples. It is a collection of samples of plant material stored at -20°C, suitable for DNA extraction. Voucher specimens for these samples are deposited at the MBG or other institutions. The material is provided to researchers against an agreement for molecular studies but not for commercial purposes such as bioprospecting, or screening for genes of interest in agricultural research.
The Bank at the
The Leslie Hill Molecular Systematics Laboratory at Kirstenbosch,
in collaboration with the Royal Botanic Gardens,
-80ºC. Each accession has a corresponding herbarium voucher.
GENE BANKS IN THE PRIVATE SECTOR
The private sector organizations, mostly multinational corporations, engaged in genetic engineering of crop plants have extensive collections of crop plant DNA. Their extensive genomic libraries are an important source of useful genes for crop improvement. However, this valuable material and information are not generally accessible to the public sector.
RESPONSIBILITIES OF DNA BANKS
The DNA banks have serious responsibilities in order to fulfill their mandates. The more important of them are:
a) Ensuring the authenticity of the scientific identity, source and geneology of the source species;
b) Adopting state of the art procedures of collection, recording, processing and preservation of DNA;
c) Maintaining quality DNA in adequate quantities;
d) Ensuring responsible use of the material supplied to others, assuring equitable benefit sharing by all parties;
e) Networking internationally, with other DNA banks, facilitating exchange of knowledge and material and to prevent duplication of efforts; and
f) Updating websites frequently and fulfilling the promises made.
September 21, 2008
CONSERVATION OF PLANT GENETIC RESOURCES
CONSERVATION OF PLANT SPECIES IN SEED BANKS
CONSERVATION OF PLANT SPECIES IN GERMPLASM BANKS