Harnessing cold adaptation for post-glacial colonisation: galactinol
synthase expression and raffinose accumulation in a polyploid and its
progenitors
Abstract
Allotetraploid white clover formed during the last glaciation through
hybridisation of two European diploid progenitors from restricted
niches: one coastal, the other alpine. Here, we examine which
hybridisation-derived molecular events may have underpinned white
clover’s post-glacial niche expansion. We compared the transcriptomic
frost responses of white clovers (inbred line and an alpine-adapted
ecotype), extant descendants of its progenitor species and a
resynthesised white clover neopolyploid to identify genes that were
exclusively frost-induced in the alpine progenitor and its derived
subgenomes. From these analyses we identified galactinol synthase, the
rate-limiting enzyme in biosynthesis of the cryoprotectant raffinose,
and found that the extant descendants of the alpine progenitor as well
as the neopolyploid white clover rapidly accumulated significantly more
galactinol and raffinose than the coastal progenitor under cold stress.
The frost-induced galactinol synthase expression and rapid raffinose
accumulation derived from the alpine progenitor likely provided an
advantage during early post-glacial colonisation for white clover
compared to its coastal progenitor.