PLANT GENOMICS AND PROTEOMICS
THIS 1C VALUE FOR THE AMOUNT OF DNA IN A PLANT NUCLEUS CAN VARY ENOR- MOUSLY FOR EXAMPLE, ONE OF THE SMALLEST GENOMES BELONGS TO ARABIDOPSIS THALIANA, WITH 125MBP, WHEREAS THE LARGEST REPORTED TO DATE BELONGS TO FRIT- ILLARIA ASSYRIACA, WITH 124,852MBP, EQUIVALENT TO 127 4PG THIS REPRESENTS A 1000-FOLD DIFFERENCE IN SIZE BETWEEN THE LARGEST AND SMALLEST GENOMES CHAR- ACTERIZED SO FAR SOME REPRESENTATIVES THAT SPAN THESE EXTREMES ARE INCLUDED IN TABLE 1 1 AND ARE TAKEN FROM THE DATABASE MAINTAINED BY THE ROYAL BOTANIC GARDENS, KEW (HTTP://WWW RBGKEW ORG UK/CVAL/HOMEPAGE HTML) HOWEVER, THIS RANGE MAY NOT REPRESENT THE TRUE LIMITS BECAUSE DNA VALUES HAVE BEEN ESTIMATED IN REPRESENTATIVES OF ONLY ABOUT 32% OF ANGIOSPERM FAMILIES (BUT ONLY REPRESENTING ABOUT 1% OF ANGIOSPERM SPECIES), 16% OF GYMNOSPERM SPECIES, AND LESS THAN 1% OF PTERIDOPHYTES AND BRYOPHYTES THIS VARIATION OCCURS NOT ONLY BETWEEN GENERA BUT ALSO WITHIN A GENUS ONE EXAMPLE IS THE GENUS ROSA, IN WHICH THERE IS A MORE THAN 11- FOLD VARIATION IN GENOME SIZE THE FACT THAT THIS RANGE IN DNA CONTENT IS NOT ASSOCIATED WITH VARIATION IN THE BASIC NUMBER OF GENES REQUIRED FOR GROWTH AND DEVELOPMENT HAS LED TO ITS BEING REFERRED TO AS THE C-VALUE PARADOX GENOME SIZE IS AN IMPORTANT BIODIVERSITY CHARACTER THAT CAN ALSO HAVE PRACTICAL IMPLICATIONS ONE EXAMPLE IS THAT THE GENOME SIZE SEEMS TO CON- STRAIN LIFE CYCLE POSSIBILITIES, IN THAT ALL OF THOSE PLANTS THAT HAVE ABOVE A CERTAIN DNA CONTENT ARE OBLIGATE PERENNIALS (BENNETT, 1972) ANOTHER EXAMPLE IS THAT SPECIES WITH LARGE AMOUNTS OF DNA (>20PG PER 1C) CAN BE PROBLEMATIC WHEN STUDYING GENETIC DIVERSITY WITH STANDARD AMPLI- ?ED FRAGMENT LENGTH POLYMORPHISM (AFLP) TECHNIQUES SUCH AS HAVE BEEN ENCOUNTERED WITH CYPRIPEDIUM CALCEOLUS (1C = 32 4PG) AND PINUS PINASTER