Genome-Wide Analysis of the Glucose-6-Phosphate Dehydrogenase Family in Soybean and Functional Identification of GmG6PDH2 Involvement in Salt Stress

Abstract

Glucose-6-phosphate dehydrogenase (G6PDH) is known as a critical enzyme responsible for nicotinamide adenine dinucleotide phosphate (NADPH) generation in the pentose phosphate pathway (PPP), and has an essential function in modulating redox homeostasis and stress responsiveness. In the present work, we characterized the nine members of the G6PDH gene family in soybean. Phylogenic analysis and transit peptide prediction showed that these soybean G6PDHs are divided into plastidic (P) and cytosolic (Cy) isoforms. The subcellular locations of five GmG6PDHs were further verified by confocal microscopy in Arabidopsis mesophyll protoplasts. The respective GmG6PDH genes had distinct expression patterns in various soybean tissues and at different times during seed development. Among them, the Cy-G6PDHs were strongly expressed in roots, developing seeds and nodules, while the transcripts of P-G6PDHs were mainly detected in green tissues. In addition, the activities and transcripts of GmG6PDHs were dramatically stimulated by different stress treatments, including salt, osmotic and alkali. Notably, the expression levels of a cytosolic isoform (GmG6PDH2) were extraordinarily high under salt stress and correlated well with the G6PDH enzyme activities, possibly implying a crucial factor for soybean responses to salinity. Enzymatic assay of recombinant GmG6PDH2 proteins expressed in Escherichia coli showed that the enzyme encoded by GmG6PDH2 had functional NADP +-dependent G6PDH activity. Further analysis indicated overexpression of GmG6PDH2 gene could significantly enhance the resistance of transgenic soybean to salt stress by coordinating with the redox states of ascorbic acid and glutathione pool to suppress reactive oxygen species generation. Together, these results indicate that GmG6PDH2 might be the major isoform for NADPH production in PPP, which is involved in the modulation of cellular AsA-GSH cycle to prevent the oxidative damage induced by high salinity.

Identification of the Cytosolic Glucose-6-Phosphate Dehydrogenase Gene from Strawberry Involved in Cold Stress Response

“…G6PDH as the key enzyme in the OPPP controls NADPH production and carbon flow, which plays an important role in plant growth, development, and stress responses [ 20 , 21 , 22 ]. Genes encoding G6PDH, a small gene family have been identified in several plants including potato [ 5 ], wheat [ 23 ], Arabidopsis [ 9 ], barley [ 24 ], tomato [ 11 ], rubber tree [ 25 ] and soybean [ 26 ]. Based on the presence of transit peptide, six FaG6PDHs in our study were divided into cytosolic and plastidic two types ( Figure 1 , Figure S1 and Table S2 ), which was in accord with previous reports [ 9 , 27 ].…”

“…G6PDH has been shown to respond to various oxidative stresses at the levels of enzyme activity and gene expression [ 31 , 32 ]. Meanwhile, the subcellular location of G6PDH seemed to have certain impacts on their stress responses [ 26 , 33 ]. Quantitative real-time PCR analyzed the expression profile of FaG6PDH gene family under cold stress.…”

“…In our study, cold stress promoted ROS production ( Figure 6 A and Figure 7 A). It has been reported that cytosolic G6PDHs participate in the modulation of cellular redox states by supplying NADPH [ 26 , 36 ]. We found that the levels of ROS were obviously lower in FaG6PDH-CY overexpression than control under cold stress, and the cellular membrane damage in cold-exposed overexpression strawberry was less severe as manifested by the notable decrease in MDA content ( Figure 6 B).…”

Transcriptome-based analysis of salt-related genes during the sprout stage of common bean (Phaseolus vulgaris) under salt stress conditions

“…The RNA was converted into single-stranded cDNA using 5 × HiScript II qRT SuperMix II (Vazyme). The qRT-PCR analysis was performed using the LightCycler 480 system (Roche Diagnostics, Switzerland) as previously described [30]. The analysis was completed with three biological replicates.…”

Overexpression of a Cytosolic 6-Phosphogluconate Dehydrogenase Gene Enhances the Resistance of Rice to Nilaparvata lugens

“…Moreover, by maintaining the redox potential necessary to protect against oxidative stress, the PPP is involved in the defense responses of plants against biotic and abiotic stresses [ 8 ], including salt and UV-B radiation [ 9 ], drought [ 10 ], cold [ 11 ], aluminum [ 12 ], and pathogen infection [ 13 ]. In soybean, for example, a cytosolic glucose-6-phosphate dehydrogenase (G6PDH, EC1.1.1.49), one of the key enzymes in the PPP which oxidizes glucose-6-phosphate to produce 6-phosphogluconolactone and NADPH, GmG6PDH2 promotes the resistance of soybean to salt stress by suppressing the salinity-induced generation of reactive oxygen species [ 14 ]. In Nicotiana tabacum , the overexpression of an engineered G6PDH in the cytosol of a Phytophthora nicotianae -susceptible tobacco cultivar enhances pathogen resistance and abiotic stress tolerance by regulating early oxidative bursts, callose deposition, and defense-related metabolic source-to-sink transitions [ 15 ].…”