Expansion of the dehydrin gene family in the Pinaceae is associated with considerable structural diversity and drought-responsive expression

Temperatures are expected to increase over the next century in all terrestrial biomes and particularly in boreal forests, where drought-induced mortality has been predicted to rise. Genomics research is helping to develop hypotheses regarding the molecular basis of drought tolerance and recent work proposed that the osmo-protecting dehydrin proteins have undergone a clade specific expansion in the Pinaceae, a major group of conifer trees. 

In a new study led by Professor John MacKay, an international team of researchers identified all of the putative members of the gene family, traced their evolutionary origin, examined their structural diversity and tested for drought-responsive expression. As a result, the team identified 41 complete dehydrin coding sequences in Picea glauca, which is four times more than most angiosperms studied to date, and more than in pines. 

Phylogenetic reconstructions indicate that the family underwent an expansion in conifers, with parallel evolution implicating the sporadic resurgence of certain amino acid sequence motifs, and a major duplication giving rise to a clade specific to the Pinaceae. A variety of plant dehydrin structures were identified with variable numbers of five different amino acid domains including assemblages specific to conifers. The expression of several of the dehydrins responded to water stress after 7–18 days without watering in spruce, reflecting changes in osmotic potential, with some sub-classes more responsive to the lack of water. 

Together, the family expansion, drought-responsive expression and structural diversification involving loss and gain of amino acid motifs suggests that sub-functionalisation has driven the diversification seen among dehydrin gene duplicates. These findings clearly indicate that dehydrins represent a large family of candidate genes for drought tolerance in spruces and in other Pinaceae that may underpin adaptability in spatially and temporally variable environments.


To read the full paper published in Tree Physiology, visit: https://academic.oup.com/treephys/article-abstract/38/3/442/4523772?redirectedFrom=fulltext