Identification of a Spermidine Synthase Gene from Soybean by Recombinant Expression, Transcriptional Verification, and Sequence Analysis

Abstract

Spermidine possesses multiple healthy functions, and soybeans contain the most abundant spermidine. In this study, spermidine contents of soybeans from different varieties and production regions in China were evaluated, and a spermidine synthase gene (speE) was identified by recombinant expression, transcriptional verification, and sequence analysis. Spermidine contents of soybean samples from 18 varieties ranged 72.38–228.82 mg/kg, and those from 19 production regions ranged 134.64–242.32 mg/kg. The highest-spermidine sample GZ was used to clone four predicted speE genes. Expressing the gene speE5 improved the spermidine titer by 54% in Bacillus amyloliquefaciens, confirming that speE5 was involved in spermidine synthesis. Transcriptional verification was performed through a soybean germination model. Germination for 48 h led to a onefold increase of spermidine in samples SHX and HB, and corresponding speE5 transcriptional levels were improved by 26-fold and 18-fold, respectively, further verifying the function of speE5. Finally, the sequences of the speE5 gene and deduced amino acids were analyzed, and the conserved sites and catalysis mechanisms were presented. This study identified an active spermidine synthase gene from soybean for the first time, which provided an important gene resource for genetic breeding of spermidine-rich soybean or microbial cell factory.

A comprehensive review of spermidine: Safety, health effects, absorption and metabolism, food materials evaluation, physical and chemical processing, and bioprocessing

“…In particular, the content of spermidine in raw soybeans ranges from 72 to 242 mg/kg (Glória et al, 2005;Nishibori et al, 2007;Pavel & Petra, 2005;Zou et al, 2020). Plant varieties as well as the planting conditions affect the spermidine contents in food materials (Plonka & Michalski, 2016).…”

“…Plant varieties as well as the planting conditions affect the spermidine contents in food materials (Plonka & Michalski, 2016). Zou et al have revealed that the spermidine content of different soybean variety is significantly different (Zou et al, 2020). Sagara et al have also proved that soybean genotypes and planting conditions had substantial effects on spermidine content (Sagara et al, 2017).…”

“…This may be one of the main reasons why the spermidine content in soybeans is usually higher than that in other grains, vegetables, and fruits (Miller‐Fleming et al., 2015; Sagara et al., 2017). In particular, the content of spermidine in raw soybeans ranges from 72 to 242 mg/kg (Glória et al., 2005; Nishibori et al., 2007; Pavel & Petra, 2005; Zou et al., 2020). Plant varieties as well as the planting conditions affect the spermidine contents in food materials (Plonka & Michalski, 2016).…”

“…In addition, it should be noted that microbial synthesis methods are green and sustainable means for production of bioactive component (Nielsen & Keasling, 2016; Xie et al., 2017). More and more research groups have been attempting to biosynthesize spermidine using metabolic engineering and synthetic biology methods (Kim et al., 2015; Kim et al., 2017; Qin et al., 2021; Zou et al., 2021; Zou et al., 2020), and the maximum spermidine titer has improved to 2.3 g/L as reported in Nature Catalysis (Qin et al., 2021). However, the present fermentation titers are relatively low and do not fulfill the requirement for commercial production (Kim et al., 2017).…”

Metabolic Engineering of Bacillus Amyloliquefaciens as A Novel Cell Factory to Produce Spermidine

“…Spermidine synthase catalyzes the transfer of the aminopropyl group from dcSAM to putrescine to form the spermidine [29], which is considered to be a rate-limiting step in biosynthesis of spermidine [30]. It is particularly essential to exploit e cient spermidine synthase genes (speE).…”