ABA Stress Research Articles

A stress-associated protein, AtSAP13, from Arabidopsis thaliana provides tolerance to multiple abiotic stresses.

Members of Stress-Associated Protein (SAP) family in plants have been shown to impart tolerance to multiple abiotic stresses, however, their mode of action in providing tolerance to multiple abiotic stresses is largely unknown. There are 14 SAP genes in Arabidopsis thaliana containing A20, AN1, and Cys2-His2 zinc finger domains. AtSAP13, a member of the SAP family, carries two AN1 zinc finger domains and an additional Cys2-His2 domain. AtSAP13 transcripts showed upregulation in response to Cd, ABA, and salt stresses. AtSAP13 overexpression lines showed strong tolerance to toxic metals (AsIII, Cd, and Zn), drought, and salt stress. Further, transgenic lines accumulated significantly higher amounts of Zn, but less As and Cd accumulation in shoots and roots. AtSAP13 promoter-GUS fusion studies showed GUS expression predominantly in the vascular tissue, hydathodes, and the apical meristem and region of root maturation and elongation as well as the root hairs. At the subcellular level, the AtSAP13-eGFP fusion protein was found to localize in both nucleus and cytoplasm. Through yeast one-hybrid assay, we identified several AP2/EREBP family transcription factors that interacted with the AtSAP13 promoter. AtSAP13 and its homologues will be highly useful for developing climate resilient crops.

The Rice OsDUF810 Family: OsDUF810.7 May be Involved in the Tolerance to Salt and Drought

With the advance of sequencing technology, the number of sequenced plant genomes has been rapidly increasing. However, understanding of the gene function in these sequenced genomes lags far behind; as a result, many coding plant sequences in public databases are annotated as proteins with domains of unknown function (DUF). Function of a protein family DUF810 in rice is not known. In this study, we analysed seven members of OsDU810 (OsDUF810.1-OsDUF810.7) family with three distinct motifs in rice Nipponbare. By phylogenetic analysis, OsDUF810 proteins fall into three major groups (I, II, III). Expression patterns of the seven corresponding OsDUF810 protein-encoding genes in 15 different rice tissues vary. Under drought, salt, cold and heat stress conditions and ABA treatment, the expression of OsDUF810.7 significantly increases. Overexpression of this protein in E. coli lead to a significant enhancement of catalase (CAT) and peroxidase (POD) activities, and improved bacterial resistance to salt and drought.

Molecular cloning and functional analysis of MbWRKY3 involved in improved drought tolerance in transformed tobacco

ABSTRACTPlant-specific WRKY transcription factors were involved in stress responses and ABA signaling. In the present study, a WRKY gene is isolated from Malus baccata (L.) Borkh and designated as MbWRKY3. Subcellular localization revealed that MbWRKY3 was localized onto nucleus. The MbWRKY3 expression levels were up-regulated by salinity, drought, and ABA treatments in M. baccata. When MbWRKY3 was introduced into tobaccos, it improved drought stress tolerance in transgenic plants. Compared to WT, the transgenic tobaccos had the higher levels of relative water content, and proline and chlorophyll contents, decreased levels of electrolyte leakage, MDA, and H2O2, increased activities of the reactive oxygen species-related enzymes (SOD, CAT, and POD), and greater up-regulations of the corresponding genes (NtSOD, NtCAT, and NtPOD), especially when dealt with drought stress. These results suggest that MbWRKY3 gene plays a positive regulatory role in drought stress response.

Enhanced multiple stress tolerance in Arabidopsis by overexpression of the polar moss peptidyl prolyl isomerase FKBP12 gene.

PaFKBP12 overexpression in Arabidopsis resulted in stress tolerance to heat, ABA, drought, and salt stress, in addition to growth promotion under normal conditions. Polytrichastrum alpinum (alpine haircap moss) is one of polar organisms that can withstand the severe conditions of the Antarctic. In this study, we report the isolation of a peptidyl prolyl isomerase FKBP12 gene (PaFKBP12) from P. alpinum collected in the Antarctic and its functional implications in development and stress responses in plants. In P. alpinum, PaFKBP12 expression was induced by heat and ABA. Overexpression of PaFKBP12 in Arabidopsis increased the plant size, which appeared to result from increased rates of cell cycle. Under heat stress conditions, PaFKBP12-overexpressing lines (PaFKBP12-OE) showed better growth and survival than the wild type. PaFKBP12-OE also showed higher root elongation rates, better shoot growth and enhanced survival at higher concentrations of ABA in comparison to the wild type. In addition, PaFKBP12-OE were more tolerant to drought and salt stress than the wild type. All these phenotypes were accompanied with higher induction of the stress responsive genes in PaFKBP12-OE than in the wild type. Taken together, our findings revealed important functions of PaFKBP12 in plant development and abiotic stress responses.

Structural and functional characterisation of two novel durum wheat annexin genes in response to abiotic stress.

Abiotic stress results in massive loss of crop productivity throughout the world. Understanding the plant gene regulatory mechanisms involved in stress responses is very important. Annexins are a conserved multigene family of Ca-dependent, phospholipid-binding proteins with suggested functions in response to environmental stresses and signalling during plant growth and development. Annexins function to counteract oxidative stress, maintain cell redox homeostasis and enhance drought tolerance. A full-length cDNA of two genes (TdAnn6 and TdAnn12) encoding annexin proteins were isolated and characterised from Tunisian durum wheat varieties (Triticum turgidum L. subsp. durum cv. Mahmoudi). Analyses of the deduced proteins encoded by annexin cDNAs (TdAnn6 and TdAnn12) indicate the presence of the characteristic four repeats of 70-75 amino acids and the motifs proposed to be involved in Ca2+ binding. Gene expression patterns obtained by real-time PCR revealed differential temporal and spatial regulation of the two annexin genes in durum wheat under different abiotic stress conditions such as salt (NaCl 150mM), osmotic (10% polyethylene glycol 8000), ionic (LiCl 10mM), oxidative (H2O2), ABA (100µM), salicylic acid (10mM), cold (4°C) and heat (37°C) stress. The two annexin genes were not regulated by heavy metal stress (CdCl2 150µM). Moreover, heterologous expression of TdAnn6 and TdAnn12 in yeast improves its tolerance to abiotic stresses, suggesting annexin's involvement in theses stress tolerance mechanisms. Taken together, our results show that the two newly isolated wheat annexin might play an active role in modulating plant cell responses to abiotic stress responses.

An Arabidopsis Nucleoporin NUP85 modulates plant responses to ABA and salt stress.

Several nucleoporins in the nuclear pore complex (NPC) have been reported to be involved in abiotic stress responses in plants. However, the molecular mechanism of how NPC regulates abiotic stress responses, especially the expression of stress responsive genes remains poorly understood. From a forward genetics screen using an abiotic stress-responsive luciferase reporter (RD29A-LUC) in the sickle-1 (sic-1) mutant background, we identified a suppressor caused by a mutation in NUCLEOPORIN 85 (NUP85), which exhibited reduced expression of RD29A-LUC in response to ABA and salt stress. Consistently, the ABA and salinity induced expression of several stress responsive genes such as RD29A, COR15A and COR47 was significantly compromised in nup85 mutants and other nucleoporin mutants such as nup160 and hos1. Subsequently, Immunoprecipitation and mass spectrometry analysis revealed that NUP85 is potentially associated with HOS1 and other nucleoporins within the nup107-160 complex, along with several mediator subunits. We further showed that there is a direct physical interaction between MED18 and NUP85. Similar to NUP85 mutations, MED18 mutation was also found to attenuate expression of stress responsive genes. Taken together, we not only revealed the involvement of NUP85 and other nucleoporins in regulating ABA and salt stress responses, but also uncovered a potential relation between NPC and mediator complex in modulating the gene expression in plants.

Abscisic acid mediated differential growth responses of root and shoot of Vigna radiata (L.) Wilczek seedlings under water stress

Water stress is a common problem in Indian agriculture and recent global climate change has aggravated this problem further. Plants have an adaptive response to water scarcity as reflected in differential root and shoot growth. In case of Vigna radiata seedlings we have observed earlier promotion of root growth while inhibition of shoot (hypocotyl) growth under mild water stress, which is probably mediated by ABA. However, the exact mechanism of ABA action is far from clear. The present study attempts to elucidate the action of ABA through apoplastic reactive oxygen species (ROS) and its impact upon antioxidant defence system during the growth of root and shoot under water stress. Thus promotion of root growth by application of exogenous ABA (10 μM) and mild water stress (ψ −0.5 MPa) may be correlated with enhanced apoplastic ROS production possibly by activating plasma membrane located NADPH oxidase (NOX) enzyme. On the contrary, in hypocotyls where growth was rather inhibited by application of water stress or ABA, neither NOX activity nor ROS accumulation was significantly detected upon these treatments. Overall activity of antioxidant enzymes [superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.1) and catalase (CAT, EC 1.11.1.6)] was high and somewhat promoted by ABA and water stress treatment in roots compared to hypocotyls. A possible ROS-mediated role of ABA in promoting growth and antioxidant activity in roots under water stress has been proposed.

A Salt Overly Sensitive Pathway Member from Brassica juncea BjSOS3 Can Functionally Complement ΔAtsos3 in Arabidopsis.

Background: Salt Overly Sensitive (SOS) pathway is a well-known pathway in arabidopsis, essential for maintenance of ion homeostasis and thus conferring salt stress tolerance. In arabidopsis, the Ca2+ activated SOS3 interacts with SOS2 which further activates SOS1, a Na+/H+ antiporter, responsible for removing toxic sodium ions from the cells. In the present study, we have shown that these three components of SOS pathway, BjSOS1, BjSOS2 and BjSOS3 genes exhibit differential expression pattern in response to salinity and ABA stress in contrasting cultivars of Brassica. It is also noticed that constitutive expression of all the three SOS genes is higher in the tolerant cultivar B. juncea as compared to the sensitive B. nigra. In silico interaction of BjSOS2 and BjSOS3 has been reported recently and here we demonstrate in vivo interaction of these two proteins in onion epidermal peel cells. Further, overexpression of BjSOS3 in corresponding arabidopsis mutant ΔAtsos3 was able to rescue the mutant phenotype and exhibit higher tolerance towards salinity stress at the seedling stage.Conclusion: Taken together, these findings demonstrate that the B. juncea SOS3 (BjSOS3) protein is a functional ortholog of its arabidopsis counterpart and thus show a strong functional conservation of SOS pathway responsible for salt stress signalling between arabidopsis and Brassica species.

Structural, expression and evolutionary analysis of the non-specific phospholipase C gene family in Gossypium hirsutum

BackgroundNonspecific phospholipase C (NPC), which belongs to a phospholipase C subtype, is a class of phospholipases that hydrolyzes the primary membrane phospholipids, such as phosphatidylcholine, to yield sn-1, 2-diacylglycerol and a phosphorylated head-group. NPC plays multiple physiological roles in lipid metabolism and signaling in plants. To fully understand the putative roles of NPC genes in upland cotton, we cloned NPC genes from Gossypium hirsutum and carried out structural, expression and evolutionary analysis.ResultsEleven NPC genes were cloned from G. hirsutum, which were found on chromosomes scaffold269.1, D03, A07, D07, A08, D11, and scaffold3511_A13. All GhNPCs had typical phosphoesterase domains and have hydrolase activity that acts on ester bonds. GhNPCs were annotated as phospholipase C, which was involved in glycerophospholipid metabolism, ether lipid metabolism, and biosynthesis of secondary metabolites. These GhNPCs showed differential expression patterns in distinct plant tissues and in response to various types of stress (low-phosphate, salt, drought, and abscisic acid). They also had different types and numbers of cis-element. GhNPCs could be classified into four subfamilies. Four pairs of GhNPCs were generated by whole-genome duplication and they underwent purifying selection.ConclusionsOur results suggested that GhNPCs are involved in regulating key abiotic stress responses and ABA signaling transduction, and they may have various functional roles for different members under complex abiotic stress conditions. Functional divergence may be the evolutionary driving force for the retention of four pairs of duplicate NPCs. Our analysis provides a solid foundation for the further functional characterization of the GhNPC gene family, and leads to potential applications in the genetic improvement of cotton cultivars.

Alternative Splicing of CIPK3 Results in Distinct Target Selection to Propagate ABA Signaling in Arabidopsis.

Calcium (Ca2+) signaling is pivotal in transmission of information in the cell. Various Ca2+ sensing molecules work to sense and relay the encrypted messages to the intended targets in the cell to maintain this signal transduction. CBL-interacting protein kinases (CIPKs) are crucial components of Ca2+ signal transduction during various abiotic stresses. Although there are intron rich CIPKs in the plant genome but very little has been reported about their alternative splicing. Moreover the physiological significance of this event in the Ca2+ signaling is still elusive. Therefore in this study, we have selected CIPK3, which has highest number of splice variants amongst Arabidopsis CIPKs. Expression profiling of five splice variants of CIPK3 by qRT-PCR in four Arabidopsis thaliana ecotypes revealed preferential transcript accumulation but similar subcellular localization of the variants and interaction with similar CBLs. ABA and drought treatment resulted in the higher accumulation of the alternately spliced transcripts of CIPK3 in Arabidopsis ecotype Wassilewkija. The transcripts of CIPK3.1 and CIPK3.4 are relatively more induced compared to other alternative splice variants. Out of four splice variants studied, we found CIPK3.1 and CIPK3.2 showing preference for ABR1, a previously reported interactor of CIPK3. We conclude that the differential expression and choice of downstream partner by CIPK3-splice variants might be one of the mechanisms of Ca2+ mediated preferential regulation of ABA and other stress signals.

Two members of unassigned type of short-chain dehydrogenase/reductase superfamily (SDR) isolated from Persicaria minor show response towards ABA and drought stress

Alcohol dehydrogenases exist as a multigene family. Two isogenes, PmADHa and PmADHb were obtained from Persicaria minor via RACE-PCR were highly identical at the 5′-UTR and ORF region and highly divergent at the 3′-UTR. With the length of 1077 and 1163 bp respectively, PmADHa and PmADHb have 801 bp ORF length, encodes 266 amino acid residues. Four nucleotides are different between the two sequences in the ORF and caused only difference one of amino acid residue at the 107th position. PmADHa and PmADHb are categorized in short-chain dehydrogenase/reductase superfamily of Unassigned type, specifically in AT3G01980.1 family. Investigations of expression profile for both genes were conducted under the treatment of 100 μM exogenous ABA and drought stress using 20% PEG-8000 in leaves, stems and roots. Exogenous ABA treatment showed that the expression of PmADHa and PmADHb were highly up-regulated only in roots. Whereas, PmADHa and PmADHb showed up-regulation in response to drought stress in all organ tested. These indicate that PmADHa and PmADHb are involved in the ABA and drought signalling pathways. Peroxisome was predicted for the subcellular localization of PmADHa and PmADHb. The promoter analysis revealed that several stress-related elements were found in the promoter of PmADHa and PmADHb and these further strengthen its relation in the stress responses.

Optimization of non-denaturing protein extraction conditions for plant PPR proteins.

Pentatricopeptide repeat proteins are one of the major protein families in flowering plants, containing around 450 members. They participate in RNA editing and are related to plant growth, development and reproduction, as well as to responses to ABA and abiotic stresses. Their characteristics have been described in silico; however, relatively little is known about their biochemical properties. Different types of PPR proteins, with different tasks in RNA editing, have been suggested to interact in an editosome to complete RNA editing. Other non-PPR editing factors, such as the multiple organellar RNA editing factors and the organelle RNA recognition motif-containing protein family, for example, have also been described in plants. However, while evidence on protein interactions between non-PPR RNA editing proteins is accumulating, very few PPR protein interactions have been reported; possibly due to their high instability. In this manuscript, we aimed to optimize the conditions for non-denaturing protein extraction of PPR proteins allowing in vivo protein analyses, such as interaction assays by co-immunoprecipitation. The unusually high protein degradation rate, the aggregation properties and the high pI, as well as the ATP-dependence of some PPR proteins, are key aspects to be considered when extracting PPR proteins in a non-denatured state. During extraction of PPR proteins, the use of proteasome and phosphatase inhibitors is critical. The use of the ATP-cofactor reduces considerably the degradation of PPR proteins. A short centrifugation step to discard cell debris is essential to avoid PPR precipitation; while in some cases, addition of a reductant is needed, probably caused by the pI/pH context. This work provides an easy and rapid optimized non-denaturing total protein extraction protocol from plant tissue, suitable for polypeptides of the PPR family.

The Application of Ultra-High-Performance Liquid Chromatography Coupled with a LTQ-Orbitrap Mass Technique to Reveal the Dynamic Accumulation of Secondary Metabolites in Licorice under ABA Stress.

The traditional medicine licorice is the most widely consumed herbal product in the world. Although much research work on studying the changes in the active compounds of licorice has been reported, there are still many areas, such as the dynamic accumulation of secondary metabolites in licorice, that need to be further studied. In this study, the secondary metabolites from licorice under two different methods of stress were investigated by ultra-high-performance liquid chromatography coupled with hybrid linear ion trap–Orbitrap mass spectrometry (UHPLC-LTQ-Orbitrap-MS). A complex continuous coordination of flavonoids and triterpenoids in a network was modulated by different methods of stress during growth. The results showed that a total of 51 secondary metabolites were identified in licorice under ABA stress. The partial least squares–discriminate analysis (PLS-DA) revealed the distinction of obvious compounds among stress-specific districts relative to ABA stress. The targeted results showed that there were significant differences in the accumulation patterns of the deeply targeted 41 flavonoids and 10 triterpenoids compounds by PCA and PLS-DA analyses. To survey the effects of flavonoid and triterpenoid metabolism under ABA stress, we inspected the stress-specific metabolic changes. Our study testified that the majority of flavonoids and triterpenoids were elevated in licorice under ABA stress, while the signature metabolite affecting the dynamic accumulation of secondary metabolites was detected. Taken together, our results suggest that ABA-specific metabolite profiling dynamically changed in terms of the biosynthesis of flavonoids and triterpenoids, which may offer new trains of thought on the regular pattern of dynamic accumulation of secondary metabolites in licorice at the metabolite level. Our results also provide a reference for clinical applications and directional planting and licorice breeding.

Genome-wide analysis of the YABBY family in soybean and functional identification of GmYABBY10 involvement in high salt and drought stresses

YABBY family is a plant specific transcription factor family, with the typical N-terminal C2C2 type zinc finger domain and the C-terminal YABBY conservative structure domain, which plays important biological roles in plant growth, development and morphogenesis. In this study, a total of 17 YABBY genes were identified in the soybean genome. The results of this research showed that 17 soybean YABBY genes were located on 11 chromosomes. Analysis of putative cis-acting elements showed that soybean YABBY genes contained lots of MYB and MYC elements. Quantitative Real-time PCR (qRT-PCR) showed that the expressions of GmYABBY3, GmYABBY10 and GmYABBY16 were more highly sensitive in drought, NaCl and ABA stresses. And the transient expression in Arabidopsis protoplasts showed that GmYABBY3 protein distributed uniformly the whole cells, while GmYABBY10 protein was mainly localized in the membranes and cytoplasm and GmYABBY16 protein was localized the nucleus and membranes. To further identify the function of GmYABBY10, we obtained the transgenic Arabidopsis overexpression GmYABBY10. Based on germination and seedling root arrays in transgenic Arabidopsis, we found that the rates of wild type seeds was a litter higher than that of GmYABBY10 transgenic seeds under both PEG and NaCl treatment. While the root length and root surface of wild type seedlings were bigger than those of GmYABBY10 transgenic seedlings. When seedlings were grown in soil, the survival rates of wild type were higher than those of transgenic plants under both PEG and NaCl treatment, which indicated that GmYABBY10 may be a negatively regulator in plant resistances to drought and salt stresses. This study provided valuable information regarding the classification and functions of YABBY genes in soybean.

Molecular cloning and characterization of PtrZPT2-1, a ZPT2 family gene encoding a Cys2/His2-type zinc finger protein from trifoliate orange (Poncirus trifoliata (L.) Raf.) that enhances plant tolerance to multiple abiotic stresses

In plants, most Cys2/His2 (C2H2) zinc finger proteins with two zinc finger domains (ZPT2) are involved in abiotic stress responses. In this study, a ZPT2 family gene PtrZPT2-1 was cloned from trifoliate orange (Poncirus trifoliata (L.) Raf.). PtrZPT2-1 is composed of 245 amino acids, has a putative molecular weight of 25.99kDa and an isoelectric point of 8.41. PtrZPT2-1 contained two C2H2 zinc finger domains, one nuclear localization signal (B-box), one transcription repression domain (DLN-box), and one protein-protein interaction domain (L-box). PtrZPT2-1 was localized to the nucleus. The PtrZPT2-1 expression was strongly induced by cold, drought, salt and ABA stresses. Overexpression of PtrZPT2-1 increased the survival rates, and the ABA, soluble sugar and proline levels but decreased the ion leakage, the malondialdehyde (MDA) content and reduced the H2O2 accumulation in the transgenic tobacco after cold, drought or salt treatments. Furthermore, the expression levels of 15 abiotic stress-related genes were significantly increased in the transgenic tobacco overexpressing PtrZPT2-1 after cold, drought or salt stress treatments. Our results indicated that overexpression of PtrZPT2-1 in the transgenic tobacco could improve the cold, drought and salt resistance of the plants by increasing the levels of osmotic regulatory solutes and decreasing the accumulation of H2O2.

Hydrogen Peroxide and Nitric Oxide Regulation of Phenolic Metabolism Under Water Stress and Aba in Wheat

Wheat cultivar PBW644 (drought tolerant) and PBW343 (drought sensitive) were found as ABA-higher sensitive and ABA-lesser sensitive, respectively, in the screen of six wheat cultivars. Both cultivars were studied for H2O2 (ROS)/nitric oxide (NO)-regulation of growth and phenolic metabolism under ABA and water stress (WS) by supplying ROS/NO producers as well as scavengers. Endogenous ROS/NO under ABA/WS increased growth, such effect was higher in PBW644. In PBW343, reduced growth under WS was improved by exogenous ROS/NO. Exogenous ROS/NO under ABA/WS decreased lignin and increased phenolics in PBW343 but such relation was not found in PBW644. Endogenous NO under WS increased flavonoids in both cultivars. Both ROS/NO under ABA/WS increased flavonoids in PBW644, however, in PBW343, only ROS increased these in roots. Under WS, PBW644 showed higher levels of cell wall peroxidase (CW-POX) and lower levels of soluble peroxidase (S-POX) than PBW343. However, under ABA, it showed higher levels of both peroxidases. ROS/NO signals under ABA increased both types of POX in both cultivars while under WS, these signals increased both types in PBW343 but CW-POX only in PBW644. Polyphenol oxidases were ABA-upregulated in PBW644 only. Under WS, these enzymes were maintained higher in PBW343. This study indicated that tolerant cultivar under WS contained sufficient endogenous ROS/NO signalling to which susceptible cultivar lacked but showed improvement on exogenous applications. Secondly, tolerant cultivar was using less phenolic activity under WS which could be due to the presence of sufficient levels of primary antioxidants.

The NADPH-oxidase AtRbohI plays a positive role in drought-stress response in Arabidopsis thaliana

As the major resource of reactive oxygen species (ROS), the NADPH oxidases (Rbohs) have been shown to play important roles in plant cells under normal growth and stress conditions. Although many family members of Rbohs were studied, little is known about the function of RbohI in Arabidopsis thaliana. Here, we report that exogenous ABA application decreases RbohI expression and mannitol significantly increases RbohI expression at transcript level. The RbohI transcripts were strongly detected in dry seeds and roots. The loss-of-function mutant rbohI exhibited sensitivity to ABA and mannitol stress during germination. Furthermore, the lateral root growth of rbohI was severely inhibited after treatment with mannitol stress. Overexpression of RbohI in Arabidopsis significantly improves the drought tolerance. Moreover, more H2O2 accumulated in RbohI overexpressors than in wild type plants in response to mannitol stress. Our conclusion is that AtRbohI functions in drought-stress response in Arabidopsis thaliana.

Identification and characterization of two waterlogging responsive alcohol dehydrogenase genes (AdADH1 and AdADH2) in Actinidia deliciosa

Previous study showed that two alcohol dehydrogenase genes (ADHs) were significantly upregulated in roots of Actinidia deliciosa after treatment with waterlogging using Illumina sequencing technology. Those two ADH genes, named AdADH1 and AdADH2, were isolated from A. deliciosa in this study. QRT-PCR analysis showed that AdADH1 and AdADH2 expression levels were significantly increased in A. deliciosa after treatment with waterlogging, NaCl, 4 °C, and heat stresses, but not ABA and drought stresses. The changes of AdADH1 and AdADH2 expression levels during waterlogging were much higher than those during other stresses. We examined the response to abiotic stresses in transgenic Arabidopsis lines in which the A. deliciosa AdADH1 and AdADH2 genes were introduced under the control of a constitutive promoter, respectively. Overexpression of A. deliciosa AdADH1 or AdADH2 in Arabidopsis could enhance waterlogging tolerance at five week old seedlings. However, the function of AdADH1 for waterlogging resistance was much better than that of AdADH2. Arabidopsis overexpressing AdADH1 gene could enhance the resistance to cold stress at five week old seedlings, but AdADH2 could not. Overexpression of AdADH1 gene enhances the resistance to salt stress at the stage of seed germination and in seedlings, and overexpression of AdADH2 gene enhances the resistance to salinity stress at the stage of seed germination but not in seedlings. However, transgenic Arabidopsis overexpressing AdADH1 or AdADH2 could not enhance to the osmotic stress at the stage of seed germination and in seedlings. These results indicated that A. deliciosa AdADH1 plays an important role in resistance to waterlogging, salinity, and cold stresses, but not drought stress, and AdADH2 plays an important role in resistance to waterlogging and salinity stresses, but not cold and drought stresses.

Functional analysis of the HD-Zip I gene ZmHDZ1 in ABA-mediated salt tolerance in rice

The homeodomain-leucine zipper I (HD-Zip I) transcription factors play crucial roles in the regulation of abiotic stress responses, whereas, up to now, most of them are still functionally unknown. In present study, we identified a maize HD-Zip I gene, designing as ZmHDZ1, and investigated its potential roles in salt stress response. The qRT-PCR results showed that expression of ZmHDZ1 was induced by ABA and salt stress. Transactivation assay and transient expression analyses indicated that ZmHDZ1 protein was located in the nucleus in tobacco leaf cells and had the transactivation activity in yeast. Over-expression of ZmHDZ1 in rice reduced tolerance to salt stress, thus, led to greater accumulation of malondialdehyde (MDA) as well as higher level of relative electrolyte leakage (REL) compared to WT plants. In addition, the transgenic seedlings also increased sensitivity to exogenous ABA. Furthermore, the expression levels of four salt responsive genes were different between transgenic and WT rice under normal or NaCl treatment. These results suggested that ZmHDZ1 function as a negative regulator in response to salt stress through the ABAmediated signal transduction pathways.

ATHB17 enhances stress tolerance by coordinating photosynthesis associated nuclear gene and ATSIG5 expression in response to abiotic stress

Photosynthesis is sensitive to environmental stress and must be efficiently modulated in response to abiotic stress. However, the underlying mechanisms are not well understood. Here we report that ARABIDOPSIS THALIANA HOMEOBOX 17 (ATHB17), an Arabidopsis HD-Zip transcription factor, regulated the expression of a number of photosynthesis associated nuclear genes (PhANGs) involved in the light reaction and ATSIG5 in response to abiotic stress. ATHB17 was responsive to ABA and multiple stress treatments. ATHB17-overexpressing plants displayed enhanced stress tolerance, whereas its knockout mutant was more sensitive compared to the wild type. Through RNA-seq and quantitative real-time reverse transcription PCR (qRT-PCR) analysis, we found that ATHB17 did not affect the expression of many known stress-responsive marker genes. Interestingly, we found that ATHB17 down-regulated many PhANGs and could directly modulate the expression of several PhANGs by binding to their promoters. Moreover, we identified ATSIG5, encoding a plastid sigma factor, as one of the target genes of ATHB17. Loss of ATSIG5 reduced salt tolerance while overexpression of ATSIG5 enhanced salt tolerance, similar to that of ATHB17. ATHB17 can positively modulate the expression of many plastid encoded genes (PEGs) through regulation of ATSIG5. Taken together, our results suggest that ATHB17 may play an important role in protecting plants by adjusting expression of PhANGs and PEGs in response to abiotic stresses.