Genome size variation in the succulent plant family Crassulaceae

Genome size (GS) refers to the total amount of DNA in the unreplicated gametic nucleus (i.e. the ۱C-value). GS can have an impact at different biological scales, from the genomic level to the whole-plant level, impacting evolutionary and ecosystem dynamics.In land plants, genome sizes exhibit an extreme diversity, ranging ca.۲,۴۰۰-fold (۰.۰۶۳-۱۵۲.۳pg/۱C).The underpinning causes of such diversity vary between species but are likely to be reflect the relative balance between genomic processes (e.g. dynamics of repetitive DNA and polyploidy) and abiotic factors which may provide an environmental filter, excluding species with large genomes from certain habitats as a result of the negative relationship of genome size with cell size and cell-cycle times.This study aims to undertake a survey of GS diversity in the succulent plant family Crassulaceae (stonecrops), consisting of approximately ۱,۴۰۰ species.The Plant DNA C-values database gives GS data for just ۴۷ Crassulaceae species.To start to fill this gap, flow cytometry was used to generate new genome size data using fresh leaf material of ۱۴۷ Crassulaceae accessions available in the living collections of the Royal Botanic Gardens,Kew, and using various plant calibration standards to convert relatative values into absolute values. Combining these new data with those in the Plant DNA C-values database showed genome size values are now available for ۱۶۲ species/cytotypes, with values ranging ۶۲-fold, from ۰.۱۴۵ to ۹.۱pg/۱C, and a mean of ۱.۹۱pg/۱C.GS was seen to be extremely diverse in Adromischus [۲.۱۱-۷.۳۰pg/۱C, based on ۲۴ species] and Sedum [۰.۱۴۵-۹.۱pg/۱C, based on ۳۸ species] and extremely conserved in Cotyledon [۲.۸۷-۳.۳۲pg (۱C), based on ۱۳ species].It is obvious that genome size plays an important role in shaping the evolution of plant genomes and impacting plant community composition at the ecosystem level, it is therefore essential to generate a comprehensive dataset of genome size across all major taxonomic groups including Crassulaceae.

کلیدواژه ها:

stonecrop family ، flow cytometry ، large genomes ، repetitive DNA