Ji-Rui Wang , Yu-Ming Wei , Mei Deng , Eviatar Nevo , Ze-Hong Yan and You-Liang Zheng
Abstract
Background
Various enzyme inhibitors act on key insect gut digestive
hydrolases, including alpha-amylases and proteinases. Alpha-amylase
inhibitors have been widely investigated for their possible use in
strengthening a plant's defense against insects that are highly
dependent on starch as an energy source. We attempted to unravel the
diversity of monomeric alpha-amylase inhibitor genes of Israeli and
Golan Heights' wild emmer wheat with different ecological factors (e.g.,
geography, water, and temperature). Population methods that analyze the
nature and frequency of allele diversity within a species and the codon
analysis method (comparing patterns of synonymous and non-synonymous
changes in protein coding sequences) were used to detect natural
selection.
Results
Three hundred and forty-eight sequences encoding monomeric
alpha-amylase inhibitors (WMAI) were obtained from 14 populations of
wild emmer wheat. The frequency of SNPs in WMAI genes was 1 out of 16.3
bases, where 28 SNPs were detected in the coding sequence. The results
of purifying and the positive selection hypothesis (p < 0.05) showed that the sequences of wmai were contributed by both natural selection and co-evolution, which ensured conservation of protein function and inhibition against diverse insect amylases. the majority of amino acid substitutions occurred at the c-terminal (positive selection domain), which ensured the stability of wmai. snps in this gene could be classified into several categories associated with water, temperature, and geographic factors, respectively.
Conclusions
Great diversity at the WMAI locus, both between and within
populations, was detected in the populations of wild emmer wheat. It was
revealed that WMAI were naturally selected for across populations by a
ratio of dN/dS as expected. Ecological factors, singly or in
combination, explained a significant proportion of the variations in the
SNPs. A sharp genetic divergence over very short geographic distances
compared to a small genetic divergence between large geographic
distances also suggested that the SNPs were subjected to natural
selection, and ecological factors had an important evolutionary role in
polymorphisms at this locus. According to population and codon analysis,
these results suggested that monomeric alpha-amylase inhibitors are
adaptively selected under different environmental conditions.