Adaptive evolution of duplicated hsp17 genes in wild barley from microclimatically divergent sites of Israel

Gene duplication is a major evolutionary driving force for establishing new gene functions. However, very little is known about the involvement of the structural divergence of recent duplicated genes in local adaptation. We evaluated the nucleotide variation of recent duplicated pair copies of the hsp17 locus for small heat shock proteins, namely, the older copy hsp17a and the younger copy hsp17b. Forty wild barley (Hordeum spontaneum) genotypes from 7 climatically divergent sites of "Evolution Canyon" I, Mount Carmel, Israel, were investigated for the sequence diversity of their hsp17 copies. We identified single nucleotide polymorphisms (SNPs) of the hsp17 locus and found 150 SNPs of hsp17a and 135 SNPs of hsp17b in the coding region. Total amino acid substitutions were present at 43 positions of hsp17a and 35 positions of hsp17b among the 7 populations. The genetic divergence and haplotype diversity were significantly different among the populations. The diversity was also correlated with microclimatic interslope divergence factors in the canyon. The natural microclimatic selection appears to adaptively diversify the duplicated copies of hsp17 of wild barley between the opposite warmer and cooler slopes, suggesting that the recent duplication of stress-responsive genes were subjected to adaptive evolution. The gene duplication and the resulting functional divergence enable plants to have better fitness in local climate change.