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Dissecting physiological and transcriptional responses of nitric oxide to drought stress by increasing in vivo nitric oxide content in Arabidopsis

ABSTRACT: Nitric oxide (NO) is involved in all major environmental stresses. However, most of these understandings were mainly based on pharmacological study using NO modulator compounds. Recently, our studies together with others provided a new class of plant experimental system with specific in vivo NO release through constitutively overexpressing rat neuronal NO synthase (nNOS) in plants. In this study, we found that the nNOS transgenic Arabidopsis plants displayed lower level of H2O2 content, but higher levels of antioxidant enzyme activities and osmolytes under drought stress conditions. Transcriptomic analysis identified 490 and 20 genes that were differentially expressed in wild type (WT) and nNOS transgenic plants under control and drought stress conditions, respectively. Pathway analysis revealed that many genes involved in photosynthesis, cell, misc, co-factor and vitamin metabolism, major CHO metabolism, OPP and secondary metabolism were largely changed in nNOS vs. WT under control or drought stress conditions. Interestingly, CBF1/2 and 13 zinc finger family proteins, known as important family of transcription regulators in modulating several stress-responsive genes, were differentially expressed by nNOS transgenic effect. Additionally, some genes were commonly regulated by nNOS transgenic and abscisic acid (ABA) effects, indicating new insights to cross-talk between ABA and NO. Taken together, in vivo NO modulated antioxidant enzyme activities, osmolyte level, and the expression of genes involved in several pathways, thereby resulting in enhanced stress tolerance in nNOS transgenic plants. These observations might provide some insights to understand the physiological and molecular mechanisms of NO in response to drought stress in Arabidopsis.

ORGANISM(S): Arabidopsis thaliana Arabidopsis

PROVIDER: GSE48474 | GEO | 2014/06/03

SECONDARY ACCESSION(S): PRJNA210265

REPOSITORIES: GEO

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Project description:Nitric oxide (NO) is involved in all major environmental stresses. However, most of these understandings were mainly based on pharmacological study using NO modulator compounds. Recently, our studies together with others provided a new class of plant experimental system with specific in vivo NO release through constitutively overexpressing rat neuronal NO synthase (nNOS) in plants. In this study, we found that the nNOS transgenic Arabidopsis plants displayed lower level of H2O2 content, but higher levels of antioxidant enzyme activities and osmolytes under drought stress conditions. Transcriptomic analysis identified 490 and 20 genes that were differentially expressed in wild type (WT) and nNOS transgenic plants under control and drought stress conditions, respectively. Pathway analysis revealed that many genes involved in photosynthesis, cell, misc, co-factor and vitamin metabolism, major CHO metabolism, OPP and secondary metabolism were largely changed in nNOS vs. WT under control or drought stress conditions. Interestingly, CBF1/2 and 13 zinc finger family proteins, known as important family of transcription regulators in modulating several stress-responsive genes, were differentially expressed by nNOS transgenic effect. Additionally, some genes were commonly regulated by nNOS transgenic and abscisic acid (ABA) effects, indicating new insights to cross-talk between ABA and NO. Taken together, in vivo NO modulated antioxidant enzyme activities, osmolyte level, and the expression of genes involved in several pathways, thereby resulting in enhanced stress tolerance in nNOS transgenic plants. These observations might provide some insights to understand the physiological and molecular mechanisms of NO in response to drought stress in Arabidopsis. Two transgenic Arabidopsis lines (nNOS-2 and nNOS-25) with the nNOS gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter, as well as Col-0 (WT), were used in this research. RNA samples from two nNOS transgenic lines were pooled for cRNA labelling and chip hybridization.

Project description:Transgenic Arabidopsis plants with constitutively low inositol (1,4,5) triphosphate exhibit an increased tolerance to water stress by an ABA-independent pathway; The phosphoinositide pathway and inositol (1,4,5) trisphopsphate (InsP3) are implicated in plant responses to stress. In order to manipulate the pathway and determine the downstream consequences of altered InsP3-mediated signaling, we generated transgenic Arabidopsis plants expressing the mammalian type I inositol polyphosphate 5-phosphatase, an enzyme that specifically hydrolyzes the soluble inositol phosphates and terminates the signal. Transgenic plants have no morphological differences compared to wild type; however, rapid transient Ca2+ responses to a cold or salt stimulus are reduced by ~ 30%. To further understand the role of InsP3-mediated signaling in plant stress responses we focused on drought stress. Surprisingly, the InsP 5-ptase plants lose less water and exhibited an increased tolerance to drought. Stomatal bioassays showed that transgenic guard cells are less responsive to the inhibition of opening by ABA but show an increased sensitivity to ABA-induced closure. The onset of the drought stress is delayed in the transgenic plants and ABA levels did not increase as much as in the wild type. Transcript profiling has revealed that DREB2A and a subset of DREB2A regulated genes are basally up regulated in the InsP 5-ptase plants. These results indicate that the drought tolerance of the InsP 5-ptase plants is mediated in part via an ABA-independent pathway. The constitutive dampening of the InsP3 signal in this system has uncovered novel regulation and cross talk between signaling pathways. Experiment Overall Design: In order to compare global expression profiles between wild type and transgenic plants in response to water stress we harvested leaves for transcript profiling at day 0 (well watered) and at day 7 when the transgenic plants were still at an RWC of >85% and the wild type and vector control plants were at an RWC of ~ 50 -60% . Leaves were harvested and pooled from ~ 10 plants of each line/time point and three independent biological replicates were carried out with wild type (WT) and 2 independent transgenic lines (T6 and T8). The vector control line (C2) was used as an additional control.

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Dissecting physiological and transcriptional responses of nitric oxide to drought stress by increasing in vivo nitric oxide content in Arabidopsis

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