Associated chromosomal DNA changes in polyploids

Abstract

The 2C and 4C nuclear DNA amounts were estimated in eight diploid species, belonging to three diverse genera (Vicia, Tephrosia, and Phlox) and their corresponding colchitetraploids. In P. drummondii, T. purpurea, and T. oxygona tetraploids the deviation from the expectation was highly significant. The DNA in P. drummondii was further discarded in subsequent (C1, C2) generations, thus attaining an overall reduction of about 25%. The DNA content in the subsequent generations was the same as that of C2. It is concluded that rapid DNA loss in the first and subsequent generations was not only associated with the substantial increase (30-66%) in the seed set, but it also helped in the establishment and stabilization of the tetraploid. The possible relationship between such a nucleotypic change and success of polyploids is discussed. The DNA change from the expected value in the P. drummondii tetraploid was achieved by equal decrement to each chromosome independent of size, i.e., small chromosomes loose the same amount of DNA as the large chromosomes.

Nuclear DNA content in the genus Hepatica (Ranunculaceae)

“…However, in our study we found that tetraploids from the crenate group (65.8-71.0 pg) contained 8.9-17.4% higher DNA content than that of the tetraploid expected from H. falconeri (2x, 30.2 pg). Polyploidization is known to play important roles in the speciation of higher plants, and the relationship between polyploidy and DNA content has been discussed in various ways (Rees and Walter 1965;Nishikawa and Furuta 1969;Bennett and Smith 1971;Furuta et al 1974;Raina et al 1994). The result of the present study suggests that the increase in the DNA content occurred after tetraploidization in the genus Hepatica, which is in accordance with the "genetic obesity hypothesis" (Soltis et al 2003) originally discussed by Bennetzen and Kellogg (1997).…”

Genome size variation and evolution in allotetraploid Arabidopsis kamchatica and its parents, Arabidopsis lyrata and Arabidopsis halleri

“…It is possible that this apparent loss in DNA content could be artefactual, due to differences between species in plant secondary compounds (Greilhuber 2005). However, rapid loss of DNA after polyploidization appears to be common in polyploids, as the 1Cx genome size has been shown to decrease as the ploidy level increases (Bennett and Thomas 1991; Raina et al 1994; Ozkan et al 2001; Leitch and Bennett 2004; Angulo and Dematteis 2013; Duchoslav et al 2013). Bennett and Thomas (1991) suggest that these changes in DNA content may have adaptive significance, perhaps because the rate of cell division is slowed considerably as genome size increases (Bennett 1972) and it may be beneficial to remove unnecessary DNA when ploidy level is high.…”

Genetic analysis of enhanced-axillary-branching-derived Eucalyptus tereticornis Smith and E. camaldulensis Dehn. plants

“…The cytophotometric analysis was carried out as described previously ( Raina et al 1994) using root/shoot meristems fixed in ice-cold, phosphate-buffered 4% formaldehyde at pH 7.0 for 2 h followed by washing in running tap water for 24 h. The meristems fixed in 1 : 3 acetic-alcohol were then hydrolyzed in 5 N HCl for 50 min at room temperature and stained for 1 h in Feulgen (Kodak) solution (pH 2.2). The stained material was washed in three changes of SO 2 water for 10 min each and firmly squashed in 50% glycerol.…”