Identification, evolutionary and expression analysis under high-salt stress of ACC synthase gene family in Glycine max (L.)

Abstract ACC synthase (ACS) is an important rate-limiting enzyme in the plant endogenous ethylene biosynthesis process and has been associated with growth and development and response to abiotic stresses s, including salt stress, in plants. The roles of ACS genes in soybean involved in salt response remains poorly understood. The findings in this study provide a crucial foundation and potential functional genes for the investigation of salt stress in soybean. In this study, 20 ACS homologs with conserved Aminotransferase class I and II domain were screened from the soybean genome. Furthermore, an expression database and Real-time quantitative reverse transcription (qRT-PCR) were used to identify the gene expression patterns in specific tissues in response to high-salt stress. Phylogenetic analysis revealed that the ACS homologs were distributed on 10 chromosomes and divided into 3 groups (Group I ~ III). 18 pairs of GmACS genes shared collinearity, and they originated from segmental replication after the second round whole genome duplication of soybean. The promoter regions of GmACS genes also contained several diverse elements related to plant hormones and stress response by cis-acting elements analysis. Gene expression analysis revealed that some genes exhibited tissue-specific expression patterns. Moreover, we identified candidate functional genes involved in response to high-salt stress in different tissues of young seedlings, including GmACS1 in root tissue. Our findings reveal novel candidate molecular components for subsequent studies on the molecular regulatory mechanisms of ACS in response to high salinity stress in soybean and functional components to facilitate further breeding of salinity-tolerant germplasm in soybean.