Genome Size Variation among and within Camellia Species by Using Flow Cytometric Analysis

Abstract

BackgroundThe genus Camellia, belonging to the family Theaceae, is economically important group in flowering plants. Frequent interspecific hybridization together with polyploidization has made them become taxonomically “difficult taxa”. The DNA content is often used to measure genome size variation and has largely advanced our understanding of plant evolution and genome variation. The goals of this study were to investigate patterns of interspecific and intraspecific variation of DNA contents and further explore genome size evolution in a phylogenetic context of the genus.Methodology/Principal FindingsThe DNA amount in the genus was determined by using propidium iodide flow cytometry analysis for a total of 139 individual plants representing almost all sections of the two subgenera, Camellia and Thea. An improved WPB buffer was proven to be suitable for the Camellia species, which was able to counteract the negative effects of secondary metabolite and generated high-quality results with low coefficient of variation values (CV) <5%. Our results showed trivial effects on different tissues of flowers, leaves and buds as well as cytosolic compounds on the estimation of DNA amount. The DNA content of C. sinensis var. assamica was estimated to be 1C = 3.01 pg by flow cytometric analysis, which is equal to a genome size of about 2940 Mb.ConclusionIntraspecific and interspecific variations were observed in the genus Camellia, and as expected, the latter was larger than the former. Our study suggests a directional trend of increasing genome size in the genus Camellia probably owing to the frequent polyploidization events.

Intraspecific variations in cardamom (Elettaria cardamomum Maton): assessment of genomic diversity by flow cytometry, cytological studies and ISSR analysis

“…2C nuclear DNA content analysis exhibited a 1.1 fold difference and thus a low level intraspecific variation in Camellia sinesnsis var. assamica (Huang et al 2013). 1C nuclear DNA content of the populations of Pinus nigra was reported to have around 23 pg (Faruk et al 2007).…”

Morphological and Cytomolecular Assessment of Intraspecific Variability in Scarlet Eggplant (Solanum aethiopicumL.)

“…Indeed, intraspecific genome size variability remains controversial as numerous earlier reports on genome size variability below the species level were dismissed due to, according to Greilhuber (2005), inaccurate methods leading to unreliable measurement results obtained in studies involving endogenous staining inhibitors (Price et al 2000;Noirot et al 2003;Beaulieu et al 2007). Among the recent methods of nuclear DNA content estimation, the most precise results are routinely obtained with flow cytometry (Doležel and Bartoš 2005), in particular when non sequence-specific intercalating fluorescent dyes such as propidium iodide (as in our study), considered the "gold standard" for measuring genome size in plants, are used (Zaitlin and Pierce 2010 (Šmarda and Bureš 2006;Zaitlin and Pierce 2010;Huang et al 2013). Therefore, the fact that the accession PI 420226 had a DNA content significantly different than those of the other accessions is most likely not a fluke, but the extent and frequency of this intraspecific variability in S. aethiopicum remains to be elucidated as probably a larger sample size representing all four groups (Kumba, Shum, Aculeatum, and Gilo) than the one used in our study needs to be evaluated for that purpose.…”

Draft genome sequence of a popular Indian tea genotype TV-1 [Camellia assamica L. (O). Kunze]

“…We report the draft genome assembly of a popular Indian tea clone TV-1. The genome size of this genotype was estimated to be 3.0 Gb with flow cytometer technique which is a close proximity with other tea genome size (Huang et al, 2013). Considering this 3.0 Gb genome size, about 136X and 13X of raw data were generated with Illumina (including PE and MP reads) and…”