Identification and Characterization of the Glucose-6-Phosphate Dehydrogenase Gene Family in the Para Rubber Tree, Hevea brasiliensis

Abstract

As a key enzyme in the pentose phosphate pathway (PPP), glucose-6-phosphate dehydrogenase (G6PDH) provides nicotinamide adenine dinucleotide phosphate (NADPH) and intermediary metabolites for rubber biosynthesis, and plays an important role in plant development and stress responses. In this study, four Hevea brasiliensis (Para rubber tree) G6PDH genes (HbG6PDH1 to 4) were identified and cloned using a genome-wide scanning approach. All four HbG6PDH genes encode functional G6PDH enzymes as shown by heterologous expression in E. coli. Phylogeny analysis and subcellular localization prediction show that HbG6PDH3 is a cytosolic isoform, while the other three genes (HbG6PDH1, 2 and 4) are plastidic isoforms. The subcellular locations of HbG6PDH3 and 4, two latex-abundant isoforms were further verified by transient expression in rice protoplasts. Enzyme activity assay and expression analysis showed HbG6PDH3 and 4 were implicated in PPP during latex regeneration, and to influence rubber production positively in rubber tree. The cytosolic HbG6PDH3 is a predominant isoform in latex, implying a principal role for this isoform in controlling carbon flow and NADPH production in the PPP during latex regeneration. The expression pattern of plastidic HbG6PDH4 correlates well with the degree of tapping panel dryness, a physiological disorder that stops the flow of latex from affected rubber trees. In addition, the four HbG6PDHs responded to temperature and drought stresses in root, bark, and leaves, implicating their roles in maintaining redox balance and defending against oxidative stress.

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

“…Our data showed differences in the expression level of GmG6PDHs in distinct tissues. To be specific, the plastidic GmG6PDHs exhibited a tissue-specific transcript profiling with the high mRNA levels in green tissue, such as leaves and pods ( Figure 5A), consistent with the expression profiles of their orthologous genes from Hevea brasiliensis, A. thaliana, and Nicotiana tabacum (Wakao and Benning, 2005;Gong et al, 2012;Long et al, 2016). By contrast, the expression analysis of cytosolic GmG6PDH genes revealed relatively high-abundant transcripts in developing seeds, roots and nodules (Figures 5A,B).…”

“…It is well-known that G6PDH genes are important for stress adaptation in several model plants (Wakao and Benning, 2005;Long et al, 2016). Also, the promoter analysis of soybean G6PDHs revealed a number of potential cis-elements and transcription binding motifs (MBS, ABRE, ARE, and TCAelements) involved in responsiveness to abiotic stresses, such as salt and drought stresses frequently encountered in our area (northeast China).…”

“…In addition, the different osmotic stresses induced by PEG6000 and mannitol have different effects on the transcription and expression of GmG6PDHs, probably due to the inhibitory effects of PEG on root oxygen availability (Guo et al, 2018). It has also been reported that the activities and transcripts of AtG6PDHs (Wakao and Benning, 2005), HbG6PDHs (Long et al, 2016), ScG6PDHs (Yang et al, 2014), and PsG6PDHs (Lin et al, 2005) are markedly stimulated by adverse environmental conditions, like oxygen availability, salinity, cold, and dehydration. Furthermore, the subcellular location of GmG6PDHs seemed to have certain impacts on their stress responses, as represented by the higher average mRNA expression levels of cytosolic GmGPDH2, 4 and 6 in comparison with plastidic GmG6PDHs under various stresses.…”

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 ].…”

Characterization of Sugar Contents and Sucrose Metabolizing Enzymes in Developing Leaves of Hevea brasiliensis

“…Quantitative real-time PCR (qPCR) was carried out using the SYBR Premix Ex Taq II (2×; Tli RNaseH Plus; TaKaRa, Dalian, China) on a CFX96 Touch TM Real-Time PCR detection system (Bio-Rad, Hercules, CA, United States). Quantification cycle values, PCR efficiency, correlation coefficients and the relative fold change of expression were determined as previously described ( Long et al, 2015 , 2016 ). The Hevea YLS8 gene was selected as an internal control based on the results of our previous work ( Li et al, 2011 ).…”