## 1 Introduction  
Preharvest sprouting (PHS) is a key agronomic issue because it can reduce grain yield and crop quality, especially of milling and baking quality wheat [1, 2], causing economic losses [3]. In Korea, the highest rainfall is in summer, with continuous rain during the harvest period, which is a major concern for wheat cultivation. Thus, controlling dormancy and germination in cereal grains and improving PHS tolerance has become a major aim of Korean wheat breeding.  
Seed dormancy is a trait that blocks germination of seeds under apparently favorable conditions. Many cereal crops, including wheat, have been selected for rapid and uniform germination, and therefore show weak dormancy, making them susceptible to PHS [4, 5]. In wheat, quantitative trait loci (QTLs) for dormancy and PHS tolerance have been studied by many researchers. [PERSON] et al. [6] utilized recombinant inbred lines (RILs) progeny populations from a cross between PHS-tolerant and -susceptible parents to study the genetic basis of dormancy and PHS tolerance, and identify the chromosomal position of QTLs for PHS tolerance. The relationships between seed color and PHS tolerance QTLs located on group 3, 4, 5, and 6 chromosomes have been studied in hexaploid wheat in Canada in breeding of white wheat [7].  
Hormonal regulation is a primary mechanism of seed dormancy and germination in seed plants. Previous studies indicated that germination is regulated by phytohormones including abscisic acid (ABA) and gibberellic acid (GA). ABA and GA are key regulators of dormancy maintenance and release, respectively, with antagonistic functions [8, 9, 10].  
[PERSON] et al. [11] investigated the expressions of ABA, GA, jasmonic acid (JA), and IAA (indole-3-acetic acid) related genes in after-ripened wheat seeds using microarray. Seed ABA levels are regulated by balanced biosynthetic and catabolic pathways [12; 13]. Genes encoding key enzymes in ABA metabolism and catabolism have been intensively studied in dormant and dormancy-released seeds [14; 15]. GA breaks dormancy and promotes germination. Typically, GA levels increase and ABA levels decrease in imbibed non-dormant seeds. Light and GA promote the degradation of ABA and the expression of the GA hormone metabolism gene increase [16]. Other phytohormones, such as auxin and cytokinin, e also associated with seed dormancy and germination. Auxin, which plays an important role in regulating plant growth and development [17; 18], regulates seed dormancy via an interaction with ABA signaling and ABI3 activation [19]. Crosstalk with cytokinin, a phytohormone that affects various plant developmental processes, has been thoroughly reviewed by [PERSON] et al. [20].  
To identify the putative key genes involved in responses to PHS and ABA treatment, RNA-seq analyses were performed. In this study, differentially expressed genes (DEGs) related to ABA and GA hormone metabolism and signaling pathways in two Korean wheat cultivars with different responses to PHS (tolerant/susceptible) were identified. Furthermore, DEGs related to auxin and cytokinin hormone metabolism and signaling were analyzed for their interactions with ABA on seed dormancy regulation. Here, we suggest the putative key genes related in phytohormone metabolism and signaling pathways for regulation of seed dormancy using comparative transcriptome analysis.