ADP-glucose pyrophosphorylase gene family in soybean and implications in drought stress tolerance.

Background: ADP-glucose pyrophosphorylase (AGPase) is the key rate-limiting enzyme in starch biosynthesis pathway, and has been identified as a potential target for manipulation strategies aimed at improving crop yield and quality.

Objective: To identify the AGPase gene family members in soybean, and explore the potential implications of GmAGPS2 in drought stress tolerance.

Methods: The genome-wide identification and sequence analysis of soybean AGPase gene family was carried out by bioinformatics methods. The GmAGP gene expression was analyzed using transcriptome data and quantitative real-time PCR (qRT-PCR). Furthermore, transgenic yeast strains overexpressing GmAGPS2 were generated, and their growth was observed under drought stress.

Results: In this study, we searched for AGPase genes (GmAGP) in the soybean genome and identified a total of 14 GmAGP genes. The GmAGP proteins had a unique conserved NTP_transferase domain and were mainly located in the chloroplast and cytosol. Evolutionarily, the GmAGP proteins can be clustered into two distinct subgroups; within the same subgroup, they displayed a similar distribution pattern of conserved motifs. The GmAGP genes exhibited an uneven distribution on 10 chromosomes, and segmental duplication contributed to AGPase gene family expansion in soybean. The GmAGP genes presented different tissue expression pattern, in which GmAGPL6, GmAGPL9, and GmAGPL10 mainly exhibited tissue-specific expression pattern. The promoter of GmAGP genes had multiple cis-acting elements related to phytohormones and stress responses, and 8 GmAGP genes contained drought-responsive cis-acting elements. qRT‒PCR analysis demonstrated a significant upregulation expression of GmAGPL6, GmAGPL10, and GmAGPS2 in response to drought stress. Further functional analysis indicated that GmAGPS2 gene could improve yeast growth under drought stress conditions and enhance the drought tolerance of yeast.

Conclusion: These results will contribute to further elucidation of the function of GmAGP genes, and offer important candidate genes for the genetic improvement of starch and yield-related traits and the breeding of high drought stress tolerance varieties in soybean.