Plant DNA Banking
The Royal Botanic Gardens, Kew's DNA Bank contains approximately 10,000 samples of plant genomic DNA (as at the beginning of year 2000), 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.
As many broad studies have been conducted in our molecular laboratory, such as the new three-gene angiosperm classification we have extracts representing all major plant groups within the bank. The bank reflects the work done in the laboratory, and we therefore have a particularly numerous orchid collection with around 2,000 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.
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-year-old DNAs 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 30 microlitre aliquots, when requested. Therefore meaning that, in theory, each sample can be used for about 30 amplifications of 30 different regions by 30 different researchers. It also means that there is no need for the repetition of extractions if new and systematically useful gene regions are discovered in the future.
Our aim, over the next few years, is to extract DNA (and voucher) all of the plant species grown at the Royal Botanic Gardens, Kew. In addition to extractions from living material we also bank samples that are extracted from our collecting expeditions around the world. Here samples are collected and dried in the field using silica gel before being brought back to the laboratory for extraction. Finally extractions are made directly from existing herbarium sheets in situations in which other sources are not available.
DNA samples are currently sent to collaborators all over world. It is our aim to open up this resource to a wider audience in the future. To achieve this end our database may eventually be put on the web.