Abstract
Gibberellins (GAs) play pivotal roles in plant growth and development, and in defenses against pathogens. Thus far, how the GA-mediated signaling pathway regulates plant defenses against herbivores remains largely unknown. In this study, we cloned the rice GA receptor gene OsGID1, whose expression was induced by damage from the brown planthopper (BPH) Niaparvata lugens, mechanical wounding, and treatment with salicylic acid (SA), but not jasmonic acid. The overexpression of OsGID1 (oe-GID1) decreased BPH-induced levels of SA, H2O2, and three SA-pathway-related WRKY transcripts, but enhanced BPH-induced levels of ethylene. Bioassays in the laboratory revealed that gravid BPH females preferred to feed and lay eggs on wild type (WT) plants than on oe-GID1 plants. Moreover, the hatching rate of BPH eggs on oe-GID1 plants was significantly lower than that on WT plants. In the field, population densities of BPH adults and nymphs were consistently and significantly lower on oe-OsGID1 plants than on WT plants. The increased resistance in oe-GID1 plants was probably due to the increased lignin level mediated by the GA pathway, and to the decrease in the expression of the three WRKY genes. Our findings illustrated that the OsGID1-mediated GA pathway plays a positive role in mediating the resistance of rice to BPH.
Highlights
In natural ecosystems, the evolutionary arms race between plants and insects has been ongoing for more than 400 million years, and along the way plants have evolved diverse strategies to protect themselves [1,2,3]
The overexpression of OsGID1 enhances the resistance of rice to brown planthopper (BPH), suggesting the OsGID1-mediated GA signaling pathway plays a role in resistance
The OsGID1 gene contains an open reading frame of 1065 nucleotides, of which it consists of two exons and one intron (Supplemental Figure S1) and encodes a soluble GA receptor of 354 amino acids, which is mainly localized in the nucleus [10]
Summary
The evolutionary arms race between plants and insects has been ongoing for more than 400 million years, and along the way plants have evolved diverse strategies to protect themselves [1,2,3]. Plants identify the type of damage caused by herbivores and trigger a signaling network comprising calcium signaling, mitogen-activated protein kinase (MAPK) cascades, and signaling pathways mediated by phytohormones, such as jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) [4,5,6]. Once activated, this signaling network elicits plants’ production of defense compounds and enhances their resistance to herbivores. There is only one GA receptor gene, OsGID1, and it encodes a soluble hormone-sensitive lipase-like protein, whereas in Arabidopsis, there are three GA receptor genes, AtGID1a, AtGID1b, and AtGID1c, and these genes function redundantly [15,18]
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