Abstract
The pentose phosphate pathway (PPP) plays an important role in plant growth and development, and plant responses to biotic and abiotic stresses. Yet, whether the PPP regulates plant defenses against herbivorous insects remains unclear. In this study, we cloned a rice cytosolic 6-phosphogluconate dehydrogenase gene, Os6PGDH1, which encodes the key enzyme catalyzing the third step in the reaction involving the oxidative phase of the PPP, and explored its role in rice defenses induced by brown planthopper (BPH) Nilaparvata lugens. Levels of Os6PGDH1 transcripts were detected in all five examined tissues, with the highest in outer leaf sheaths and lowest in inner leaf sheaths. Os6PGDH1 expression was strongly induced by mechanical wounding, infestation of gravid BPH females, and jasmonic acid (JA) treatment. Overexpressing Os6PGDH1 (oe6PGDH) decreased the height of rice plants and the mass of the aboveground part of plants, but slightly increased the length of plant roots. In addition, the overexpression of Os6PGDH1 enhanced levels of BPH-induced JA, jasmonoyl-isoleucine (JA-Ile), and H2O2, but decreased BPH-induced levels of ethylene. Bioassays revealed that gravid BPH females preferred to feed and lay eggs on wild-type (WT) plants over oe6PGDH plants; moreover, the hatching rate of BPH eggs raised on oe6PGDH plants and the fecundity of BPH females fed on these were significantly lower than the eggs and the females raised and fed on WT plants. Taken together, these results indicate that Os6PGDH1 plays a pivotal role not only in rice growth but also in the resistance of rice to BPH by modulating JA, ethylene, and H2O2 pathways.
Highlights
The results indicate that Os6PGDH1 regulates rice growth and development
To test whether Os6PGDH1 influences the biosynthesis of signal molecules, we examined the levels of these molecules in transgenic and WT
brown planthopper (BPH)-induced salicylic acid (SA) levels in oe6PGDH lines were similar to those in WT plants (Figure S4). These results suggest that in rice, Os6PGDH1 is involved in the biosynthesis of BPH-induced jasmonic acid (JA), JA-Ile, H2 O2, and ethylene, but not SA
Summary
Plants recognize herbivore-associated molecular patterns via cell-membrane-localized receptors and initiate early signaling events, such as the activation of mitogen-activated protein kinase (MAPK) cascades and the burst of reactive oxygen species (ROS) [1]. 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]. We found that the overexpression of Os6PGDH1 increases the BPH-induced accumulation of JA, JA-Ile, and H2 O2 , but decreases ethylene levels, resulting in the enhanced resistance of rice to BPH. This suggests that the Os6PGDH1-mediated PPP plays a role in the resistance of rice to herbivores
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