High temperature inhibited the accumulation of anthocyanin by promoting ABA catabolism in sweet cherry fruits.

Color is an essential appearance characteristic of sweet cherry (Prunus avium L.) fruits and mainly determined by anthocyanin. Temperature plays an important role in the regulation of anthocyanin accumulation. In this research, anthocyanin, sugar, plant hormone and related gene expression were analyzed using physiological and transcriptomic methods in order to reveal the effects of high temperature on fruit coloring and the related mechanism. The results showed that high temperature severely inhibited anthocyanin accumulation in fruit peel and slowed the coloring process. The total anthocyanin content in fruit peel increased by 455% and 84% after 4 days of normal temperature treatment (NT, 24°C day/14°C night) and high temperature treatment (HT, 34°C day/24°C night), respectively. Similarly, the contents of 8 anthocyanin monomers were significantly higher in NT than in HT. HT also affected the levels of sugars and plant hormones. The total soluble sugar content increased by 29.49% and 16.81% in NT and HT, respectively, after 4 days of treatment. The levels of ABA, IAA and GA20 also increased in both the two treatments but more slowly in HT. Conversely, the contents of cZ, cZR and JA decreased more rapidly in HT than in NT. The results of the correlation analysis showed that the ABA and GA20 contents were significantly correlated with the total anthocyanin contents. Further transcriptome analysis showed that HT inhibited the activation of structural genes in anthocyanin biosynthesis as well as the repression of CYP707A and AOG, which dominated the catabolism and inactivation of ABA. These results indicate that ABA may be a key regulator in the high-temperature-inhibited fruit coloring of sweet cherry. High temperature induces higher ABA catabolism and inactivation, leading to lower ABA levels and finally resulting in slow coloring.

Functional physiological phenotyping and transcriptome analysis provide new insight into strawberry growth and water consumption.

Global warming is expected to increase agricultural water scarcity; thus, optimized irrigation schedules are important and timely for sustainable crop production. Deficit irrigation, which balances crop growth and water consumption, has been proposed, but the critical threshold is not easily quantified. Here, we conducted experiments on strawberry plants subjecting progressive drought following various water recovery treatments on the high-throughput physiological phenotyping system "Plantarray". The critical soil water contents (θcri), below which the plant transpiration significantly decreased, were calculated from the inflection point of the transpiration rate (Tr) - volumetric soil water content (VWC) curve fitted by a piecewise function. The physiological traits of water relations were compared between the well-watered plants (CK), plants subjecting the treatment of rewatering at the point of θcri following progressive drought (WR_θcri), and the plants subjecting the treatment of rewatering at severe drought following progressive drought (WR_SD). The results showed that midday Tr, daily transpiration (E), and biomass gain of the plants under WR_θcri treatment were equivalent to CK during the whole course of the experiment, but those under WR_SD treatment were significantly lower than CK during the water stress phase that could not recover even after rehydration. To explore the gene regulatory mechanisms, transcriptome analysis of the samples collected 12 h before, 12 h post and 36 h post water recovery in the three treatments was conducted. GO and KEGG enrichment analyses for the differentially expressed genes indicated that genes involved in mineral absorption and flavonoid biosynthesis were among the most striking transcriptionally reversible genes under the WR_θcri treatment. Functional physiological phenotyping and transcriptome data provide new insight into a potential, quantitative, and balanceable water-saving strategy for strawberry irrigation and other agricultural crops.

Effects of soil treated fungicide fluopimomide on tomato (Solanum lycopersicum L.) disease control and plant growth.

Fluopimomide is a novel acid amide fungicide registered for the control of many plant pathogens. In the present study, the effects of soil-treated fluopimomide on soil micro biomass, disease incidence, plant growth, soil enzyme activity, and marketable yield of tomato (Solanum lycopersicum L.) were investigated via field trial. In addition, the application prospect in China was also evaluated. In the experiment, five treatments with three replications and a randomized complete block design were followed. The treatments were: furrow application of fluopimomide (25% suspension concentrate, SC) at the dosage of 375, 750, and 1,500 g ha-1, which was recommended, double recommended, and quadruple recommended dosages, respectively. Besides, common control fungicide fluopicolide (5% SC) furrow was applied at recommended application dosages of 750 mL ha-1, and a non-treated control was also undertaken. Results indicated that fluopimomide exhibited no effects on the amount of soil bacteria and actinomycetes, and its inhibition effect on fungi amount could be recovered at 60 days after treatment (DAT). With the recommended application dosage, fluopimomide could efficiently reduce the number of plant pathogens in soil by 79.56-85.80%, significantly reduce the disease incidences in tomato plants by 80.00-88.24%, and improve plant height by 13.25-24.05% and marketable yield by 16.88%. Furthermore, soil enzymes exhibited a complex response to fluopimomide, and AOB and nifH gene copy numbers were increased by the double and quadruple recommended dosage of fluopimomide. Based on the above results, fluopimomide could be recommended as an efficient fungicide for the tomato field.

Downregulation of hsa_circ_0004543 Activates oxLDL-Induced Vascular Endothelial Cell Proliferation and Angiogenesis.

Circular RNAs (circRNAs) are novel non-coding RNAs, which show abnormal expression in several diseases, such as atherosclerosis (AS). The purpose of the present study was to reveal the association between hsa_circ_0004543 and AS. In the present study, hsa_circ_0004543 was overexpressed in human umbilical vein endothelial cells (HUVECs) induced by oxidized low-density lipoprotein (oxLDL). Inhibition of hsa_circ_0004543 expression facilitated the proliferation, migration, and invasion of HUVECs and significantly reduced their apoptotic rate following treatment with oxLDL. Furthermore, silencing of hsa_circ_0004543 activated the PI3K/AKT/NOS3 pathway in oxLDL-induced HUVECs. Collectively, these results demonstrated that hsa_circ_0004543 may play a vital role in the development of AS and affect the proliferation of HUVECs, providing a potential target for treating endothelial cell damage in AS.

Transcriptomic analysis reveals insights into the response to Hop stunt viroid (HSVd) in sweet cherry (Prunus avium L.) fruits.

Hop stunt viroid (HSVd) is a member of the genus Hostuviroid of the family Pospiviroidae and has been found in a wide range of herbaceous and woody hosts. It causes serious dapple fruit symptoms on infected sweet cherry, notably inducing cherry tree decay. In order to better understand the molecular mechanisms of HSVd infection in sweet cherry fruit, transcriptome analysis of HSVd-infected and healthy sweet cherry fruits was carried out. A total of 1,572 differentially expressed genes (DEGs) were identified, involving 961 upregulated DEGs and 611 downregulated DEGs. Functional analysis indicated that the DEGs were mainly involved in plant hormone signal transduction, plant-pathogen interactions, secondary metabolism, and the MAPK signaling pathway. In addition, C2H2 zinc finger, MYB, bHLH, AP2/ERF, C2C2-dof, NAC and WRKY transcription factors can respond to HSVd infection. In order to confirm the high-throughput sequencing results, 16 DEGs were verified by RT-qPCR analysis. The results provided insight into the pathways and genes of sweet cherry fruit in response to HSVd infection.

SIRT3 is a downstream target of PPAR-α implicated in high glucose-induced cardiomyocyte injury in AC16 cells.

Diabetic cardiomyopathy (DCM) is a worldwide public health concern that continues to display rapid growth trends. This study investigated the function of sirtuin 3 (SIRT3), a primary mitochondrial deacetylase with important roles in antioxidant defense and oxidative metabolism, during high glucose-induced cardiomyocyte (AC16 cell) injury. Peroxisome proliferator-activated receptor-α (PPAR-α) is directly related to the occurrence of DCM. Hence, we further examined the relationship between SIRT3 and PPAR-α. AC16 cells were treated with various concentrations of glucose. Relative mRNA expression and protein levels were detected by RT-qPCR and western blot analysis, respectively. Cell proliferation and apoptosis were assessed using CCK8 and Annexin V-FITC apoptosis detection kits, respectively. DCFH-DA assay was used to measure reactive oxygen species (ROS) accumulation. The results indicated that high glucose treatment reduced the expression of mRNA and protein of SIRT3 and PPAR-α in AC16 cells. Moreover, high glucose inhibited cell proliferation, as well as induced apoptosis, intracellular hydrogen peroxide production, and JNK1/2 phosphorylation. These effects were antagonized by SIRT3 overexpression or treatment with the PPAR-α agonist, Wy14643. Conversely, inhibition of SIRT3 via 3-TYP led to similar phenomena as those induced by high glucose treatment in AC16 cells, which were blocked by Wy14643. Lastly, chromatin immunoprecipitation (ChIP) and luciferase assays demonstrated SIRT3 as a direct target of PPAR-α. Taken together, the results provide evidence for an important role of SIRT3 in high glucose-induced cardiomyocyte injury and regulation of JNK1/2 signaling. Further, SIRT3 is a direct downstream target of PPAR-α.

Chromosome-scale genome assembly of sweet cherry (Prunus avium L.) cv. Tieton obtained using long-read and Hi-C sequencing.

Sweet cherry (Prunus avium) is an economically significant fruit species in the genus Prunus. However, in contrast to other important fruit trees in this genus, only one draft genome assembly is available for sweet cherry, which was assembled using only Illumina short-read sequences. The incompleteness and low quality of the current sweet cherry draft genome limit its use in genetic and genomic studies. A high-quality chromosome-scale sweet cherry reference genome assembly is therefore needed. A total of 65.05 Gb of Oxford Nanopore long reads and 46.24 Gb of Illumina short reads were generated, representing ~190x and 136x coverage, respectively, of the sweet cherry genome. The final de novo assembly resulted in a phased haplotype assembly of 344.29 Mb with a contig N50 of 3.25 Mb. Hi-C scaffolding of the genome resulted in eight pseudochromosomes containing 99.59% of the bases in the assembled genome. Genome annotation revealed that more than half of the genome (59.40%) was composed of repetitive sequences, and 40,338 protein-coding genes were predicted, 75.40% of which were functionally annotated. With the chromosome-scale assembly, we revealed that gene duplication events contributed to the expansion of gene families for salicylic acid/jasmonic acid carboxyl methyltransferase and ankyrin repeat-containing proteins in the genome of sweet cherry. Four auxin-responsive genes (two GH3s and two SAURs) were induced in the late stage of fruit development, indicating that auxin is crucial for the sweet cherry ripening process. In addition, 772 resistance genes were identified and functionally predicted in the sweet cherry genome. The high-quality genome assembly of sweet cherry obtained in this study will provide valuable genomic resources for sweet cherry improvement and molecular breeding.

A de novo assembly of the sweet cherry (Prunus avium cv. Tieton) genome using linked-read sequencing technology.

The sweet cherry (Prunus avium) is one of the most economically important fruit species in the world. However, there is a limited amount of genetic information available for this species, which hinders breeding efforts at a molecular level. We were able to describe a high-quality reference genome assembly and annotation of the diploid sweet cherry (2n = 2x = 16) cv. Tieton using linked-read sequencing technology. We generated over 750 million clean reads, representing 112.63 GB of raw sequencing data. The Supernova assembler produced a more highly-ordered and continuous genome sequence than the current P. avium draft genome, with a contig N50 of 63.65 KB and a scaffold N50 of 2.48 MB. The final scaffold assembly was 280.33 MB in length, representing 82.12% of the estimated Tieton genome. Eight chromosome-scale pseudomolecules were constructed, completing a 214 MB sequence of the final scaffold assembly. De novo, homology-based, and RNA-seq methods were used together to predict 30,975 protein-coding loci. 98.39% of core eukaryotic genes and 97.43% of single copy orthologues were identified in the embryo plant, indicating the completeness of the assembly. Linked-read sequencing technology was effective in constructing a high-quality reference genome of the sweet cherry, which will benefit the molecular breeding and cultivar identification in this species.

Induction of competent cells for Agrobacterium tumefaciens-mediated stable transformation of common bean (Phaseolus vulgaris L.).

Stable transformation of common bean (Phaseolus vulgaris L.) has been successful, to date, only using biolistic-mediated transformation and shoot regeneration from meristem-containing embryo axes. In this study, using precultured embryo axes, and optimal co-cultivation conditions resulted in a successful transformation of the common bean cultivar Olathe using Agrobacterium tumefaciens strain EHA105. Plant regeneration through somatic embryogenesis was attained through the preculture of embryo axes for 12 weeks using induced competent cells for A. tumefaciens-mediated gene delivery. Using A. tumefaciens at a low optical density (OD) of 0.1 at a wavelength of 600 nm for infection and 4-day co-cultivation, compared to OD600 of 0.5, increased the survival rate of the inoculated explants from 23% to 45%. Selection using 0.5 mg L-1 glufosinate (GS) was effective to identify transformed cells when the bialaphos resistance (bar) gene under the constitutive 35S promoter was used as a selectable marker. After an 18-week selection period, 1.5% -2.5% inoculated explants, in three experiments with a total of 600 explants, produced GS-resistant plants through somatic embryogenesis. The expression of bar was confirmed in first- and second-generation seedlings of the two lines through reverse polymerase chain reaction. Presence of the bar gene was verified through genome sequencing of two selected transgenic lines. The induction of regenerable, competent cells is key for the successful transformation, and the protocols described may be useful for future transformation of additional Phaseolus germplasm.

VcRR2 regulates chilling-mediated flowering through expression of hormone genes in a transgenic blueberry mutant.

The molecular mechanism underlying dormancy release and the induction of flowering remains poorly understood in woody plants. Mu-legacy is a valuable blueberry mutant, in which a transgene insertion caused increased expression of a RESPONSE REGULATOR 2-like gene (VcRR2). Mu-legacy plants, compared with nontransgenic 'Legacy' plants, show dwarfing, promotion of flower bud formation, and can flower under nonchilling conditions. We conducted transcriptomic comparisons in leaves, chilled and nonchilled flowering buds, and late-pink buds, and analyzed a total of 41 metabolites of six groups of hormones in leaf tissues of both Mu-legacy and 'Legacy' plants. These analyses uncovered that increased VcRR2 expression promotes the expression of a homolog of Arabidopsis thaliana ENT-COPALYL DIPHOSPHATE SYNTHETASE 1 (VcGA1), which induces new homeostasis of hormones, including increased gibberellin 4 (GA4) levels in Mu-legacy leaves. Consequently, increased expression of VcRR2 and VcGA1, which function in cytokinin responses and gibberellin synthesis, respectively, initiated the reduction in plant height and the enhancement of flower bud formation of the Mu-legacy plants through interactions of multiple approaches. In nonchilled flower buds, 29 differentially expressed transcripts of 17 genes of five groups of hormones were identified in transcriptome comparisons between Mu-legacy and 'Legacy' plants, of which 22 were chilling responsive. Thus, these analyses suggest that increased expression of VcRR2 was collectively responsible for promoting flower bud formation in highbush blueberry under nonchilling conditions. We report here for the first time the importance of VcRR2 to induce a suite of downstream hormones that promote flowering in woody plants.

Complete Genome Sequence of a Little Cherry Virus-2 Isolate from Sweet Cherry in China.

The first complete genome sequence of a little cherry virus-2 (LChV-2-TA) isolate from China was determined using small RNA deep sequencing combined with overlapping reverse transcriptase PCR (RT-PCR). Phylogenetic analysis revealed that LChV-2-TA grouped in a well-supported cluster with members of the genus Ampelovirus with close relationships to previously reported LChV-2 isolates.

Constitutive Expression of an Apple FLC3-like Gene Promotes Flowering in Transgenic Blueberry under Nonchilling Conditions.

MADS-box transcription factors FLOWERING LOCUS C (FLC) and APETALA1 (AP1)/CAULIFLOWER (CAL) have an opposite effect in vernalization-regulated flowering in Arabidopsis. In woody plants, a functional FLC-like gene has not been verified through reverse genetics. To reveal chilling-regulated flowering mechanisms in woody fruit crops, we conducted phylogenetic analysis of the annotated FLC-like proteins of apple and found that these proteins are grouped more closely to Arabidopsis AP1 than the FLC group. An FLC3-like MADS-box gene from columnar apple trees (Malus domestica) (MdFLC3-like) was cloned for functional analysis through a constitutive transgenic expression. The MdFLC3-like shows 88% identity to pear's FLC-like genes and 82% identity to blueberry's CAL1 gene (VcCAL1). When constitutively expressed in a highbush blueberry (Vaccinium corymbosum L.) cultivar 'Legacy', the MdFLC3-like induced expressions of orthologues of three MADS-box genes, including APETALA1, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1, and CAL1. As a consequence, in contrast to the anticipated late flowering associated with an overexpressed FLC-like, the MdFLC3-like promoted flowering of transgenic blueberry plants under nonchilling conditions where nontransgenic 'Legacy' plants could not flower. Thus, the constitutively expressed MdFLC3-like in transgenic blueberries functioned likely as a blueberry's VcCAL1. The results are anticipated to facilitate future studies for revealing chilling-mediated flowering mechanisms in woody plants.

Complete chloroplast genome of Prunus canescens: an endemic shrub in China.

Prunus canescens is an endemic cherry species in China, which is distributed in Shaanxi, Gansu, Hubei, and Sichuan provinces of China. The chloroplast (cp) genome of P. canescens is 157,890 bp in size containing 125 unique genes, including 8 rRNA genes, 37 tRNA genes, and 80 protein-coding genes (PCGs). Phylogenetic analysis exhibited that P. canescens is most related to P. pseudocerasus.

Complete nucleotide sequence of little cherry virus 1 (LChV-1) infecting sweet cherry in China.

Little cherry virus 1 (LChV-1), associated with little cherry disease (LCD), has a significant impact on fruit quality of infected sweet cherry trees. We report the full genome sequence of an isolate of LChV-1 from Taian, China (LChV-1-TA), detected by small-RNA deep sequencing and amplified by overlapping RT-PCR. The LChV-1-TA genome was 16,932 nt in length and contained nine open reading frames (ORFs), with sequence identity at the overall genome level of 76%, 76%, and 78% to LChV-1 isolates Y10237 (UW2 isolate), EU715989 (ITMAR isolate) and JX669615 (V2356 isolate), respectively. Based on the phylogenetic analysis of HSP70h amino acid sequences of Closteroviridae family members, LChV-1-TA was grouped into a well-supported cluster with the members of the genus Velarivirus and was also closely related to other LChV-1 isolates. This is the first report of the complete nucleotide sequence of LChV-1 infecting sweet cherry in China.

[Determination of anthocyanins in the peel of sweet cherry by ultra performance liquid chromatography tandem mass spectrometry].

A method for the determination of seven anthocyanins in the peel of sweet cherry was developed by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was extracted by methanol containing 0.1% (v/v) hydrochloric acid, and then purified by AB-8 macroporous resins. The separation was carried out on a Phenomenex Kinetex column (100 mm x 4.6 mm, 2.6 Rm) with mobile phase of 0.1% (v/v) formic acid aqueous solution containing 5 mmol/L ammonium formate and methanol. The sample solution was detected by UPLC-MS/MS with ESI under positive ion and multi reaction monitoring (MRM) modes. The results showed that the limits of quantification (LOQs) for the seven target compounds were 0.26-1.42 µg/kg. The seven anthocyanin standards showed a good linearity in the range of 0-100 µg/L with the correlation coefficients (r2) of 0.996 4-0.999 3. The average recoveries of the seven anthocyanins were 97.2%-105.4%, and the relative standard deviations (RSDs) were 1.9%-5.8%. The mature fruit samples of sweet cherry red variety "Tieton" and the yellow variety "13-33" were analyzed by this method. The results showed that the anthocyanin composition and contents were significantly different between the two varieties. This method can be used for rapid identification and the determination of anthocyanin components in sweet cherry fruits due to its simple operation, high sensitivity, good reproducibility and covering a wide range of anthocyanins.

Comparative transcriptome analysis of genes involved in anthocyanin biosynthesis in the red and yellow fruits of sweet cherry (Prunus avium L.).

BACKGROUND: Fruit color is one of the most important economic traits of the sweet cherry (Prunus avium L.). The red coloration of sweet cherry fruit is mainly attributed to anthocyanins. However, limited information is available regarding the molecular mechanisms underlying anthocyanin biosynthesis and its regulation in sweet cherry. METHODOLOGY/PRINCIPAL FINDINGS: In this study, a reference transcriptome of P. avium L. was sequenced and annotated to identify the transcriptional determinants of fruit color. Normalized cDNA libraries from red and yellow fruits were sequenced using the next-generation Illumina/Solexa sequencing platform and de novo assembly. Over 66 million high-quality reads were assembled into 43,128 unigenes using a combined assembly strategy. Then a total of 22,452 unigenes were compared to public databases using homology searches, and 20,095 of these unigenes were annotated in the Nr protein database. Furthermore, transcriptome differences between the four stages of fruit ripening were analyzed using Illumina digital gene expression (DGE) profiling. Biological pathway analysis revealed that 72 unigenes were involved in anthocyanin biosynthesis. The expression patterns of unigenes encoding phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavanone 3'-hydroxylase (F3'H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS) and UDP glucose: flavonol 3-O-glucosyltransferase (UFGT) during fruit ripening differed between red and yellow fruit. In addition, we identified some transcription factor families (such as MYB, bHLH and WD40) that may control anthocyanin biosynthesis. We confirmed the altered expression levels of eighteen unigenes that encode anthocyanin biosynthetic enzymes and transcription factors using quantitative real-time PCR (qRT-PCR). CONCLUSIONS/SIGNIFICANCE: The obtained sweet cherry transcriptome and DGE profiling data provide comprehensive gene expression information that lends insights into the molecular mechanisms underlying anthocyanin biosynthesis. These results will provide a platform for further functional genomic research on this fruit crop.

Rapid detection of Prunus necrotic ringspot virus using magnetic nanoparticle-assisted reverse transcription loop-mediated isothermal amplification.

Prunus necrotic ringspot virus (PNRSV) has seriously reduced the yield of Prunus species worldwide. In this study, a highly efficient and specific two-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed to detect PNRSV. Total RNA was extracted from sweet cherry leaf samples using a commercial kit based on a magnetic nanoparticle technique. Transcripts were used as the templates for the assay. The results of this assay can be detected using agarose gel electrophoresis or by assessing in-tube fluorescence after adding SYBR Green I. The assay is highly specific for PNRSV, and it is more sensitive than reverse-transcription polymerase chain reaction (RT-PCR). Restriction enzyme digestion verified further the reliability of this RT-LAMP assay. To our knowledge, this is the first report of the application of RT-LAMP to PNRSV detection in Prunus species.

Expression analysis of five maize MAP kinase genes in response to various abiotic stresses and signal molecules.

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules in eukaryotes. Plant MAPK cascades are complicated networks and play vital roles in signal transduction induced by biotic and abiotic stresses. In this paper, expression patterns of MAPKs in maize roots treated with low-temperature, osmotic stresses, wounding, plant hormones and UV-C irradiation were investigated. Semi-quantitative RT-PCR reveals that the expression of MAPKs in maize roots which treated with low-temperature in light or in low light are inducible. The expression patterns of MAPKs in maize roots with treatments of CaCl2, SA, GA and wounding are approximately the same. A detailed time course experiment shows that the expression patterns of ZmSIMK are different with treatments of PEG and NaCl, respectively. These results suggest that the expression patterns of MAPKs are complicated and the signal pathways are interlaced into a network in maize roots.

Overexpression of maize mitogen-activated protein kinase gene, ZmSIMK1 in Arabidopsis increases tolerance to salt stress.

Mitogen-activated protein kinase (MAPK) cascades play a remarkably crucial role in plants. It has been studied intensively in model plants Arabidopsis, tobacco and rice. However, the function of MAPKs in maize (Zea mays L.) has not been well documented. ZmSIMK1 (Zea mays salt-induced mitogen-activated protein kinase 1) is a previously identified MAPK gene in maize. In this research, we charactered ZmSIMK1 and showed that ZmSIMK1 was involved in Arabidopsis salt stress. The genomic organization of ZmSIMK1 gene and its expression in maize have been analyzed. In order to investigate the function of ZmSIMK1, we generated transgenic Arabidopsis constitutively overexpressing ZmSIMK1. Ectopic expression of ZmSIMK1 in Arabidopsis resulted in increased resistance against salt stress. Importantly, ZmSIMK1-overexpressing Arabidopsis exhibited constitutive expression of stress-responsive marker genes, RD29A and P5CS1. Furthermore, RD29A and P5CS1 were upregulated under salt stress. These results suggest that ZmSIMK1 may play an important role in plant salt stress.

Abscisic acid and hydrogen peroxide induce a novel maize group C MAP kinase gene, ZmMPK7, which is responsible for the removal of reactive oxygen species.

Mitogen-activated protein kinase (MAPK) cascades are involved in biotic and abiotic stress responses. In plants, MAPKs are classified into four groups, designated A-D. Information about group C MAPKs is limited, and, in particular, no data from maize are available. In this article, we isolated a novel group C MAPK gene, ZmMPK7, from Zea mays. Exogenous abscisic acid (ABA) and hydrogen peroxide (H(2)O(2)) induced calcium-dependant transcription of ZmMPK7. Induction of this gene in response to ABA was blocked by several reactive oxygen species (ROS) manipulators such as imidazole, Tiron, and dimethylthiourea (DMTU). This result indicates that endogenous H(2)O(2) may be required for ZmMPK7-mediated ABA signaling. Expression of ZmMPK7 in Nicotonia tobaccum caused less H(2)O(2) to accumulate and alleviated ROS-mediated injuries following submission of the plants to osmotic stress. The enhanced total peroxidase (POD) activity in transgenic tobacco plants may contribute to removal of ROS. Finally, we have shown that the ZmMPK7 protein localizes in the nucleus. These results broaden our knowledge regarding plant group C MAPK activity in response to stress signals.