Abstract
KEY MESSAGE: ipa1 enhances rice drought tolerance mainly through activating the ABA pathway. It endows rice seedlings with a more developed root system, smaller leaf stomata aperture, and enhanced carbon metabolism. Drought is a major abiotic stress to crop production. IPA1 (IDEAL PLANT ARCHITECTURE 1)/OsSPL14 encodes a transcription factor and has been reported to function in both rice ideal plant architecture and biotic resistance. Here, with a pair of IPA1 and ipa1-NILs (Near Iso-genic Lines), we found that ipa1 could significantly improve rice drought tolerance at seedling stage. The ipa1 plants had a better-developed root system and smaller leaf stomatal aperture. Analysis of carbon-nitrogen metabolism-associated enzyme activity, gene expression, and metabolic profile indicated that ipa1 could tip the carbon-nitrogen metabolism balance towards an increased carbon metabolism pattern. In both the control and PEG-treated conditions, ABA content in the ipa1 seedlings was significantly higher than that in the IPA1 seedlings. Expression of the ABA biosynthesis genes was detected to be up-regulated, whereas the expression of ABA catabolism genes was down-regulated in the ipa1 seedlings. In addition, based on yeast one-hybrid assay and dual-luciferase assay, IPA1 was found to directly activate the promoter activity of OsHOX12, a transcription factor promoting ABA biosynthesis, and OsNAC52, a positive regulator of the ABA pathway. The expression of OsHOX12 and OsNAC52 was significantly up-regulated in the ipa1 plants. Combined with the previous studies, our results suggested that ipa1 could improve rice seedling drought tolerance mainly through activating the ABA pathway and that regulation of the ipa1-mediated ABA pathway will be an important strategy for improving drought resistance of rice.
Highlights
Plants live in fixed locations and face diverse abiotic stresses negatively affecting plant growth and seed production
Combined with the previous studies, our results suggested that ipa[1] could improve rice seedling drought tolerance mainly through activating the Abscisic acid (ABA) pathway and that regulation of the ipa1mediated ABA pawthway will be an important strategy for improving drought resistance of rice
ABA is induced in response to adverse environmental conditions, and it plays a critical role in regulating abiotic stress response in plants (Cutler, et al 2010)
Summary
Plants live in fixed locations and face diverse abiotic stresses (such as drought, salinity, and cold) negatively affecting plant growth and seed production. The understanding of plant responses to stresses in physiology, genetics, and molecular biology will be greatly helpful in improving the tolerance of plants to abiotic stresses through genetic engineering (Huang, et al 2009). Rice nced[3] mutants had increased sensitivity to water and H2O2 stress, increased stomata aperture, delayed leaf senescence, and decreased ABA content, while overexpression of OsNCED3 could enhance rice water stress tolerance, promote leaf senescence and increase ABA content (Huang, et al 2018). Overexpression seedlings were hypersensitive to drought stress with decreased ABA content, indicating OsABA8ox[3] gene plays an important role in controlling ABA level and drought stress resistance in rice (Cai, et al 2015). Great progress has been made in understanding the roles of IPA1 in rice plant development and biotic resistance, its function in rice abiotic stresse tolerance is still unknown. By using a pair of the IPA1/ipa1-NILs (Near Iso-genic Lines), we found that ipa[1] could significantly improve rice drought tolerance at the seedling stage mainly through activating ABA pathway
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