Abstract
Abscisic acid (ABA) plays a fundamental role in plant growth and development, as well as in the responses to abiotic stresses. Previous studies have revealed that many components in ABA and drought stress signaling pathways are ubiquitinated by E3 ligases. In this study, AtPPRT1, a putative C3HC4 zinc-finger ubiquitin E3 ligase, was explored for its role in abiotic stress response in Arabidopsis thaliana. The expression of AtPPRT1 was induced by ABA. In addition, the β-glucuronidase (GUS) gene driven by the AtPPRT1 promoter was more active in the root hair zone and root tips of primary and major lateral roots of young seedlings in the presence of ABA. The assays for seed germination, stomatal aperture, root length, and water deficit demonstrated that the AtPPRT1-overexpressing Arabidopsis was insensitive to ABA and sensitive to drought stress compared with wild-type (WT) plants. The analysis by quantitative real-time PCR (qRT-PCR) revealed that the expression of three stress-inducible genes (AtRAB18, AtERD10, and AtKIN1) were upregulated in the atpprt1 mutant and downregulated in AtPPRT1-overexpressing plants, while two ABA hydrolysis genes (AtCYP707A1 and AtCYP707A3) were downregulated in the atpprt1 mutant and upregulated in AtPPRT1-overexpressing plants in the presence of ABA. AtPPRT1 was localized in the mitochondria. Our findings indicate that AtPPRT1 plays a negative role in ABA and drought stress responses.
Highlights
As sessile organisms, plants face fluctuating environments that are often unsuitable for growth and development
In order to study the biological function of AtPPRT1 in Arabidopsis, we identified an atpprt1 mutant and constructed AtPPRT1-overexpressing lines
We found that AtPPRT1-overexpressing lines showed a lower tolerance to drought and compared with WT plants, plants overexpressing AtPPRT1 were insensitive to abscisic acid (ABA)
Summary
Plants face fluctuating environments that are often unsuitable for growth and development These adverse environmental conditions include biotic and abiotic stresses, such as pathogen infection and herbivore attack, drought, heat, radiation, cold, high salt, and so on. ABA plays a vital role in many aspects of plants, including seed dormancy and germination, root growth, seedling development, and the adaptive response to environmental stresses such as drought, salt, cold, and other abiotic stresses [6,7,8,9]. Many ABA signaling components have been identified, such as ABA receptors, phosphatases, kinases, transcription factors, and ABA-regulated genes [9] Among these components, there are several that are usually subjected to post-translational modifications, including phosphorylation, sumoylation, and ubiquitination [9,11,12,13]. Our analysis demonstrates that AtPPRT1 acts as a negative regulator in ABA and drought stress responses
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