Data from: Adaptive evolution and divergent expression of heat stress transcription factors in grasses

Background: Heat stress transcription factors (Hsfs) regulate gene
expression in response to heat and many other environmental stresses in
plants. Understanding the adaptive evolution of Hsf genes in the grass
family will provide potentially useful information for the genetic
improvement of modern crops to handle increasing global temperatures.
Results: In this work, we performed a genome-wide survey of Hsf genes in 5
grass species, including rice, maize, sorghum, Setaria, and Brachypodium,
by describing their phylogenetic relationships, adaptive evolution, and
expression patterns under abiotic stresses. The Hsf genes in grasses were
divided into 24 orthologous gene clusters (OGCs) based on phylogeneitc
relationship and synteny, suggesting that 24 Hsf genes were present in the
ancestral grass genome. However, 9 duplication and 4 gene-loss events were
identified in the tested genomes. A maximum-likelihood analysis revealed
the effects of positive selection in the evolution of 11 OGCs and
suggested that OGCs with duplicated or lost genes were more readily
influenced by positive selection than other OGCs. Further investigation
revealed that positive selection acted on only one of the duplicated genes
in 8 of 9 paralogous pairs, suggesting that neofunctionalization
contributed to the evolution of these duplicated pairs. We also
investigated the expression patterns of rice and maize Hsf genes under
heat, salt, drought, and cold stresses. The results revealed divergent
expression patterns between the duplicated genes. Conclusions: This study
demonstrates that neofunctionalization by changes in expression pattern
and function following gene duplication has been an important factor in
the maintenance and divergence of grass Hsf genes.