Abstract
BackgroundGlucose-6-phosphate dehydrogenase (G6PDH or G6PD) functions in supply of NADPH, which is required for plant defense responses to stresses. However, whether G6PD functions in the abscisic acid (ABA) signaling pathway remains to be elucidated. In this study, we investigated the involvement of the cytosolic G6PD5 in the ABA signaling pathway in Arabidopsis.ResultsWe characterized the Arabidopsis single null mutant g6pd5. Phenotypic analysis showed that the mutant is more sensitive to ABA during seed germination and root growth, whereas G6PD5-overexpressing plants are less sensitive to ABA compared to wild type (WT). Furthermore, ABA induces excessive accumulation of reactive oxygen species (ROS) in mutant seeds and seedlings. G6PD5 participates in the reduction of H2O2 to H2O in the ascorbate-glutathione cycle. In addition, we found that G6PD5 suppressed the expression of Abscisic Acid Insensitive 5 (ABI5), the major ABA signaling component in dormancy control. When G6PD5 was overexpressed, the ABA signaling pathway was inactivated. Consistently, G6PD5 negatively modulates ABA-blocked primary root growth in the meristem and elongation zones. Of note, the suppression of root elongation by ABA is triggered by the cell cycle B-type cyclin CYCB1.ConclusionsThis study showed that G6PD5 is involved in the ABA-mediated seed germination and root growth by suppressing ABI5.
Highlights
Glucose-6-phosphate dehydrogenase (G6PDH or G6PD) functions in supply of NADPH, which is required for plant defense responses to stresses
Responsiveness of g6pd mutants and G6PD5overexpressing lines to abscisic acid (ABA) treatment during seed germination and root growth ABA is significantly induced by stresses and its signaling has an important function in abiotic stress responses
The g6pd5 mutant did not display any visible phenotype at the germination and seedling stages compared to wild type (WT) under normal growth conditions (Fig. 1a-c)
Summary
Glucose-6-phosphate dehydrogenase (G6PDH or G6PD) functions in supply of NADPH, which is required for plant defense responses to stresses. Whether G6PD functions in the abscisic acid (ABA) signaling pathway remains to be elucidated. We investigated the involvement of the cytosolic G6PD5 in the ABA signaling pathway in Arabidopsis. The main regulatory step of OPPP is catalysed by glucose-6-phosphate dehydrogenase (G6PDH or G6PD). Many experiments have proven that G6PD is induced by adverse biotic and abiotic stresses, including salinity, drought and ABA [7,8,9,10,11]. Recent studies showed that G6PD plays a primary role in stress responses, favoring ROS-scavenging functions [23]. During drought stress, plant cells increase their needs for reducing power in order to sustain the antioxidant defense system and counteract ROS accumulation and consequent damages [23, 24]
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