Whole Genome Duplications -
None in Amborella?
None in Amborella?
Comparing molecular evolutionary rates between duplicated gene
sequences that do NOT entail changes in resulting proteins can provide
a crude measure of the age of the duplication in question. In this
example, this rate of change (Ks) was calculated for pairs of duplicated
genes from different plants. Water lily (Nuphar) shows a pattern seen
in a number of other angiosperms: many duplicate pairs (expressed by
their frequency) with low Ks values (i.e., young age), a trailing off of
numbers of pairs with increasing Ks, followed by a 'hump' of many
duplicate pairs centering around Ks = 0.5.
The expected distribution of gene pairs given a simple process of birth
and death of duplicates is shown by the green line.
The hump of many older duplication events around K = 0.5, however, is
suggestive of a single underlying cause, i.e., a whole genome
duplication. The expectation for such an event is shown by the fitted
black line. (The smaller hump in Nuphar [yellow fitted line] at higher Ks
likely represents an older whole genome duplication.)
Importantly, neither Amborella nor the gymnosperms Pinus or
Welwitschia show masses of duplicate pairs at similar age, as
represented by Ks = ca. 0.5. In fact, Amborella and Pinus show no
evidence whatsoever for whole genome duplication during their
evolutionary histories. A likely inference is that a whole genome
duplication occurred along the stem lineage of all living angiosperms
clades except Amborella.
Modified from Cui et al. (2006), based on data from Albert et al. (2005).
sequences that do NOT entail changes in resulting proteins can provide
a crude measure of the age of the duplication in question. In this
example, this rate of change (Ks) was calculated for pairs of duplicated
genes from different plants. Water lily (Nuphar) shows a pattern seen
in a number of other angiosperms: many duplicate pairs (expressed by
their frequency) with low Ks values (i.e., young age), a trailing off of
numbers of pairs with increasing Ks, followed by a 'hump' of many
duplicate pairs centering around Ks = 0.5.
The expected distribution of gene pairs given a simple process of birth
and death of duplicates is shown by the green line.
The hump of many older duplication events around K = 0.5, however, is
suggestive of a single underlying cause, i.e., a whole genome
duplication. The expectation for such an event is shown by the fitted
black line. (The smaller hump in Nuphar [yellow fitted line] at higher Ks
likely represents an older whole genome duplication.)
Importantly, neither Amborella nor the gymnosperms Pinus or
Welwitschia show masses of duplicate pairs at similar age, as
represented by Ks = ca. 0.5. In fact, Amborella and Pinus show no
evidence whatsoever for whole genome duplication during their
evolutionary histories. A likely inference is that a whole genome
duplication occurred along the stem lineage of all living angiosperms
clades except Amborella.
Modified from Cui et al. (2006), based on data from Albert et al. (2005).
