Introduction to the DNA Bank
The DNA Bank
The RBG Kew DNA Bank contains approximately 40,000 samples of plant genomic DNA (as at the beginning of 2010), all stored at -80°C. DNA is extracted from particular taxa of interest that are then databased with information on names, collectors, localities etc. Each sample is vouchered (made into a herbarium specimen). DNA samples are currently sent to collaborators all over world. It is our aim to facilitate taxonomic and evolutionary studies world-wide.
As many broad studies have been conducted in RBG Kew's molecular lab, we have extracts representing all major plant groups within the bank. The Bank reflects the work done in the lab, and we therefore have a particularly numerous orchid collection with around 5500 DNA samples. We also have a number of samples from rare and endangered species. Finally there are multiple representatives within some species that are used in population study projects.
Aims of the DNA Bank
RBG Kew is committed to honouring the letter and the spirit of the Convention on Biological Diversity, and its agreements with partner countries, and accordingly some material is restricted. Our aim, over the next few years, is to extract DNA (and voucher) all plant species grown at RBG Kew. In addition to extractions from living material, we also bank samples that are extracted from RBG Kew collecting-expeditions around the world, if we have permission from the country of origin to do so. Here samples are collected and dried in the field using silica gel before being brought back to the lab for extraction. Finally extractions are made directly from existing herbarium sheets in situations in which other sources are not available.
Method of Extraction
All of the DNAs in the bank have been through an extensive extraction protocol, which includes a standard CTAB-chloroform extraction then ethanol precipitation and washing, followed by density gradient cleaning and dialysis. The samples are cleaned to such an extent that they are stable at ambient temperatures for days while in transit. In storage within the bank they are, in theory, stable indefinitely. For example, we have 10 or greater year-old DNA samples that still amplify without problems. This system is more economical than storing plant material in any other form (e.g. silica gel) because it can be used by many researchers. Typically about 1ml of DNA is produced from our extraction protocol, which can be split and sent out as 25µl aliquots, when requested. Therefore meaning that there is no need for the repetition of extractions if new and systematically useful gene regions are discovered in the future.