Genome-wide characterization and expression analysis of TOPP-type protein phosphatases in soybean (Glycine max L.) reveal the role of GmTOPP13 in drought tolerance

Background: In response to various abiotic stressors such as drought, many plants engage different protein phosphatases linked to several physiological and developmental processes. However, comprehensive analysis of this gene family is lacking for soybean.

Objective: This study was performed to identify the TOPP-type protein phosphatase family in soybean and investigate the gene's role under drought stress.

Methods: Soybean genome sequences and transcriptome data were downloaded from the Phytozome v.12, and the microarray data were downloaded from NCBI GEO datasets GSE49537. Expression profiles of GmTOPP13 were obtained based on qRT-PCR results. GmTOPP13 gene was transformed into tobacco plants via Agrobacterium mediated method, and the drought tolerance was analyzed by water deficit assay.

Results: 15 GmTOPP genes were identified in the soybean genome database (GmTOPP1-15). GmTOPP genes were distributed on 9 of 20 chromosomes, with similar exon-intron structure and motifs arrangement. All GmTOPPs contained Metallophos and STPPase_N domains as well as the core catalytic sites. Cis-regulatory element analysis predicted that GmTOPPs were widely involved in plant development, stress and hormone response in soybean. Expression profiles showed that GmTOPPs expressed in different tissues and exhibited divergent expression patterns in leaf and root in response to drought stimulus. Moreover, GmTOPP13 gene was isolated and expression pattern analysis indicated that this gene was highly expressed in seed, root, leaf and other tissues detected, and intensively induced upon PEG6000 treatment. In addition, overexpression of GmTOPP13 gene enhanced the drought tolerance in tobacco plants. The transgenic tobacco plants showed regulation of stress-responsive genes including CAT, SOD, ERD10B and TIP during drought stress.

Conclusions: This study provides valuable information for the study of GmTOPP gene family in soybean, and lays a foundation for further functional studies of GmTOPP13 gene under drought and other abiotic stresses.