An Arabidopsis Cytokinin-Modifying Glycosyltransferase UGT76C2 Improves Drought and Salt Tolerance in Rice.

Ting Wang,Yanjie Li,Pan Li,Chengchao Zheng,Fangfei Liu,Bingkai Hou

doi:10.3389/fpls.2020.560696

Ting Wang, Yanjie Li + Show 4 more

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https://doi.org/10.3389/fpls.2020.560696

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Abstract

Drought and salt stresses are common environmental threats that negatively affect rice development and yield. Here we report that the overexpression of AtUGT76C2, a cytokinin glycosyltransferase, in rice modulates cytokinin homeostasis and confers the plants an eminent property in drought and salt tolerance. The transgenic plants exhibit sensitivity to salt and drought stress as well as abscisic acid during the germination stage and the postgermination stage while showing enhanced tolerance to drought and salinity at the young seedling stage and the mature stage. The overexpression of UGT76C2 decreases the endogenous cytokinin level and enhances root growth, which greatly contributes to stress adaptation. In addition, the transgenic plants also show enhanced ROS scavenging activity, reduced ion leakage under salt stress, smaller stomatal opening, and more proline and soluble sugar accumulation, which demonstrate that UGT76C2 acts as an important player in abiotic stress response in rice. To explore the molecular mechanism of UGT76C2 in response to stress adaptation, the expressions of eight stress-responsive genes including OsSOS1, OsPIP2.1, OsDREB2A, OsCOIN, OsABF2, OsRAB16, OsP5CR, and OsP5CS1 were detected, which showed notable upregulation in UGT76C2 overexpression plants under salt and drought stresses. Our results reveal that the ectopic expression of AtUGT76C2 confers the transgenic rice many traits in improving drought and salt stress tolerance in both developmental and physiological levels. It is believed that AtUGT76C2 could be a promising candidate gene for cultivating saline- and drought-tolerant rice.

Highlights

Drought and salinity are the most common abiotic threats limiting plant growth and crop yield
Many stress-regulated genes have been identified to improve stress resistance in plants, which can be grouped into four types: genes involved in the synthesis of osmotic regulators, such as proline biosynthesis gene OsP5CS1 and OsP5CR (Hu et al, 1992; Sripinyowanich et al, 2013); genes involved in ion transportation, such as SOS1 (Shi et al, 2000); antioxidant-related genes, such as CAT, APX, and SOD (Mhamdi et al, 2010; Verma et al, 2019); and genes regulating signaling cascades, such as protein kinases (Kang et al, 2017), transcription factors, and so on (Xiong et al, 2014; Chen et al, 2015)
To determine the role of the Arabidopsis UGT76C2 in rice, transgenic plants overexpressing AtUGT76C2 under the control of the maize ubiquitin promoter were generated, and the homozygous lines were selected with hygromycin. qRT-PCR analysis indicated that the transcripts of AtUGT76C2 could be detected in transgenic plants, but not in WT plants (Figure 1A)

Summary

Introduction

Drought and salinity are the most common abiotic threats limiting plant growth and crop yield. Drought and salinity have become major factors causing rice yield loss. UGT76C2 Improves Rice Stress Tolerance critical saline- and drought-tolerant genes as well as revealing their molecular mechanisms is a critical prerequisite for cultivating saline- and drought-tolerant rice via molecular design breeding. Many stress-regulated genes have been identified to improve stress resistance in plants, which can be grouped into four types: genes involved in the synthesis of osmotic regulators, such as proline biosynthesis gene OsP5CS1 and OsP5CR (Hu et al, 1992; Sripinyowanich et al, 2013); genes involved in ion transportation, such as SOS1 (Shi et al, 2000); antioxidant-related genes, such as CAT (catalase), APX (ascorbate peroxidase), and SOD (superoxide dismutase) (Mhamdi et al, 2010; Verma et al, 2019); and genes regulating signaling cascades, such as protein kinases (Kang et al, 2017), transcription factors, and so on (Xiong et al, 2014; Chen et al, 2015). To enrich the present knowledge and uncover the molecular mechanism on stress regulation in every aspect, more pathways still need to be elucidated

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