Identification and Analysis of the GASR Gene Family in Common Wheat (Triticum aestivum L.) and Characterization of TaGASR34, a Gene Associated With Seed Dormancy and Germination

Abstract

Seed dormancy and germination are important agronomic traits in wheat (<i>Triticum aestivum</i> L.) because they determine pre-harvest sprouting (PHS) resistance and thus affect grain production. These processes are regulated by <i>Gibberellic Acid-Stimulated Regulator</i> (<i>GASR</i>) genes. In this study, we identified 37 <i>GASR</i> genes in common wheat, which were designated <i>TaGASR1-37</i>. Moreover, we identified 40 pairs of paralogous genes, of which only one had a Ka/Ks value greater than 1, indicating that most <i>TaGASR</i> genes have undergone negative selection. Chromosomal location and duplication analysis revealed 25 pairs of segmentally duplicated genes and seven pairs of tandemly duplicated genes, suggesting that large-scale duplication events may have contributed to the expansion of <i>TaGASR</i> gene family. Microarray analysis of the expression of 18 <i>TaGASR</i> genes indicated that these genes play diverse roles in different biological processes. Using wheat varieties with contrasting seed dormancy phenotypes, we investigated the expression patterns of <i>TaGASR</i> genes and the corresponding seed germination index phenotypes in response to water imbibition, exogenous ABA and GA treatment, and low- and high-temperature treatment. Based on these data, we identified the <i>TaGASR34</i> gene as potentially associated with seed dormancy and germination. Further, we used a SNP mutation of the <i>TaGASR34</i> promoter (-16) to develop the CAPS marker GS34-7B, which was then used to validate the association of <i>TaGASR34</i> with seed dormancy and germination by evaluating two natural populations across environments. Notably, the frequency of the high-dormancy <i>GS34-7Bb</i> allele was significantly lower than that of the low-dormancy <i>GS34-7Ba</i> allele, implying that the favorable <i>GS34-7Bb</i> allele has not previously been used in wheat breeding. These results provide valuable information for further functional analysis of <i>TaGASR</i> genes and present a useful gene and marker combination for future improvement of PHS resistance in wheat.