Over-Expression of Oshox4 Enhances Drought and Salinity Tolerance in Rice
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Over-Expression of Oshox4 Enhances Drought and Salinity Tolerance in Rice W. Q. Zhoua,*, Y. Q. Zhoua, C. Y. Heb, B. Q. Mouc, and W. Zhoud,** a
Crop Research Institute, Gansu Academy of Agriculture Sciences, Lanzhou, 730070 PR China Department of Gansu University of Chinese Medicine, Lanzhou,730020 PR China c Agricultural Research Service (USDA-ARS), US Department of Agriculture, Salinas, CA, 93905 United States dGenetic Transformation Lab, Plant Breeding Genetics and Biology Division, International Rice Research Institute, Metro Manila, 7777 Philippines *e-mail: [email protected] **e-mail: [email protected] bPharmacy
Received May 13, 2020; revised May 13, 2020; accepted May 13, 2020
Abstract—Plant hormones play major roles in abiotic stress. This study shows that gibberellin acid-inefficient transgenic rice (Oryza sativa L.) is more tolerant to drought and salinity stress. We also investigated the underlying molecular mechanism by which plants respond to salinity and drought stress. We previously showed how the HD-Zip family I gene Oshox4 (Homeobox 4) regulates GA deactivation by controlling DELLA subfamily and rice GA 2-oxidase and GA 3-oxidase genes in rice. Here we investigated the role of rice Oshox4 gene for drought and salinity stress tolerance. Phenotypic analysis indicated that Oshox4 transgenic lines are more tolerant to drought and salinity stress relative to non-transgenic IR64 plants. To explain the strong osmotic stress tolerance of Oshox4 transgenic lines, we studied the expression of rice GA 2-oxidase, rice YABBY, rice KRP, and rice GRAS gene families. qRT-PCR results showed that OsGA2ox4, OsGA2ox6, OsGA2ox8, OsGAI and OsSCRL were highly expressed under severe drought in Oshox4 transgenic plants. Oshox4 enhanced the expression of OsGA2ox5, OsKRP2 and OsKRP5 under 50 mM salt treatment and OsSCRL under 200 mM salt treatment. Our findings have confirmed that Oshox4 transgenic rice plants are more tolerant to drought and salinity stress and that Oshox4 plays a role in rice osmatic tolerance. This study provides novel insights into methods of maintaining higher yield amidst a limited supply of water by improving physiological conditions. Keywords: Oryza sativa, Oshox4, rice, drought stress, salinity stress, over-expression DOI: 10.1134/S1021443720060205
INTRODUCTION Water deficit is considered a major abiotic factor that cans severe decrease the productivity of rice and other crops. In about 1.5 billion hectares of the cropland, only 16% of these areas are equipped for irrigation [1]. The water crisis may intensify and become more frequent this century as a result of population, exploration, arable land desertification and the increase of industrial water use [2]. Predictions show that severe and widespread droughts in many land areas may occur within the coming century and are mainly due to a reduction in precipitation and/or enhanced evaporation [3, 4]. In fact, the risk of severe drought in many parts of the world is much higher and Abbreviations: ABA—abscisic acid; CDKs—cycli
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