Comparative Proteomics Profiling Illuminates the Fruitlet Abscission Mechanism of Sweet Cherry as Induced by Embryo Abortion.

Sweet cherry (Prunus avium L.) is a delicious nutrient-rich fruit widely cultivated in countries such as China, America, Chile, and Italy. However, the yield often drops severely due to the frequently-abnormal fruitlet abscission, and few studies on the metabolism during its ripening process at the proteomic level have been executed so far. To get a better understanding regarding the sweet cherry abscission mechanism, proteomic analysis between the abscising carpopodium and non-abscising carpopodium of sweet cherry was accomplished using a newly developed Liquid chromatography-mass spectrometry/mass spectrometry with Tandem Mass Tag (TMT-LC-MS/MS) methodology. The embryo viability experiments showed that the vigor of the abscission embryos was significantly lower than that of retention embryo. The activity of cell wall degrading enzymes in abscising carpopodium was significantly higher than that in non-abscising carpopodium. The anatomy results suggested that cells in the abscission zone were small and separated. In total, 6280 proteins were identified, among which 5681 were quantified. It has been observed that differentially accumulated proteins (DAPs) influenced several biological functions and various subcellular localizations. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that plenty of metabolic pathways were notably enriched, particularly those involved in phytohormone biosynthesis, cell wall metabolism, and cytoskeletal metabolism, including 1-aminocyclopropane-1-carboxylate oxidase proteins which promote ethylene synthesis, and proteins promoting cell wall degradation, such as endoglucanases, pectinase, and polygalacturonase. Differential expression of proteins concerning phytohormone biosynthesis might activate the shedding regulation signals. Up-regulation of several cell wall degradation-related proteins possibly regulated the shedding of plant organs. Variations of the phytohormone biosynthesis and cell wall degradation-related proteins were explored during the abscission process. Furthermore, changes in cytoskeleton-associated proteins might contribute to the abscission of carpopodium. The current work represented the first study using comparative proteomics between abscising carpopodium and non-abscising carpopodium. These results indicated that embryo abortion might lead to phytohormone synthesis disorder, which effected signal transduction pathways, and hereby controlled genes involved in cell wall degradation and then caused the abscission of fruitlet. Overall, our data may give an intrinsic explanation of the variations in metabolism during the abscission of carpopodium.

Correction: Li, et al. Conserved miR396b-GRF Regulation Is Involved in Abiotic Stress Responses in Pitaya (Hylocereus polyrhizus). Int. J. Mol. Sci. 2019, 20, 2501.

The authors wish to make the following corrections to this paper [...].

Conserved miR396b-GRF Regulation Is Involved in Abiotic Stress Responses in Pitaya (Hylocereus polyrhizus).

MicroRNA396 (miR396) is a conserved microRNA family that targets growth-regulating factors (GRFs), which play significant roles in plant growth and stress responses. Available evidence justifies the idea that miR396-targeted GRFs have important functions in many plant species; however, no genome-wide analysis of the pitaya (Hylocereus polyrhizus) miR396 gene has yet been reported. Further, its biological functions remain elusive. To uncover the regulatory roles of miR396 and its targets, the hairpin sequence of pitaya miR396b and the open reading frame (ORF) of its target, HpGRF6, were isolated from pitaya. Phylogenetic analysis showed that the precursor miR396b (MIR396b) gene of plants might be clustered into three major groups, and, generally, a more recent evolutionary relationship in the intra-family has been demonstrated. The sequence analysis indicated that the binding site of hpo-miR396b in HpGRF6 is located at the conserved motif which codes the conserved "RSRKPVE" amino acid in the Trp-Arg-Cys (WRC) region. In addition, degradome sequencing analysis confirmed that four GRFs (GRF1, c56908.graph_c0; GRF4, c52862.graph_c0; GRF6, c39378.graph_c0 and GRF9, c54658.graph_c0) are hpo-miR396b targets that are regulated by specific cleavage at the binding site between the 10th and 11th nucleotides from the 5' terminus of hpo-miR396b. Furthermore, quantitative real-time polymerase chain reaction (qRT-PCR) analysis showed that hpo-miR396b is down-regulated when confronted with drought stress (15% polyethylene glycol, PEG), and its expression fluctuates under other abiotic stresses, i.e., low temperature (4 ± 1 °C), high temperature (42 ± 1 °C), NaCl (100 mM), and abscisic acid (ABA; 0.38 mM). Conversely, the expression of HpGRF6 showed the opposite trend to exposure to these abiotic stresses. Taken together, hpo-miR396b plays a regulatory role in the control of HpGRF6, which might influence the abiotic stress response of pitaya. This is the first documentation of this role in pitaya and improves the understanding of the molecular mechanisms underlying the tolerance to drought stress in this fruit.

Molecular cytogenetic map visualizes the heterozygotic genome and identifies translocation chromosomes in Citrus sinensis.

Citrus sinensis is the most cultivated and economically valuable Citrus species in the world, whose genome has been assembled by three generation sequencings. However, chromosome recognition remains a problem due to the small size of chromosomes, and difficulty in differentiating between pseudo and real chromosomes because of a highly heterozygous genome. Here, we employ fluorescence in situ hybridization (FISH) with 9 chromosome painting probes, 30 oligo pools, and 8 repetitive sequences to visualize 18 chromosomes. Then, we develop an approach to identify each chromosome in one cell through single experiment of oligo-FISH and Chromoycin A3 (CMA) staining. By this approach, we construct a high-resolution molecular cytogenetic map containing the physical positions of CMA banding and 38 sequences of FISH including centromere regions, which enables us to visualize significant differences between homologous chromosomes. Based on the map, we locate several highly repetitive sequences on chromosomes and estimate sizes and copy numbers of each site. In particular, we discover the translocation regions of chromosomes 4 and 9 in C. sinensis "Valencia." The high-resolution molecular cytogenetic map will help improve understanding of sweet orange genome assembly and also provide a fundamental reference for investigating chromosome evolution and chromosome engineering for genetic improvement in Citrus.

Does noninvasive cerebellar stimulation improve the balance and walking function of patients with stroke: A meta-analysis of randomized controlled trials.

OBJECTIVES: Investigating the efficacy and safety of noninvasive cerebellar stimulation in improving the balance and walking function of patients with stroke. METHODS: We searched 7 databases for randomized controlled trials (RCTs) related to noninvasive cerebellar stimulation in the treatment of stroke. The Berg Balance Scale (BBS), 6-minute walk test (6MWT), and Barthel Index (BI) were used as the outcome indexes to evaluate balance, walking and activities of daily living (ADL). The quality of the research was evaluated using the Cochrane Risk of Bias Tool. A meta-analysis was performed to evaluate the difference between the noninvasive cerebellar stimulation and control groups. Heterogeneity tests were performed to assess differences in treatment effects across noninvasive cerebellar stimulation modalities. A sensitivity analysis was performed to evaluate the robustness of the results. RESULTS: Seven studies were included, and 5 articles (71.43%) were rated as having a low risk of bias. Among the primary outcome indicators, 4 of the 7 articles were combined into the fixed effect model (I2 = 38%, P = .18). Compared with the control group, noninvasive cerebellar stimulation improved the BBS score, and the difference was statistically significant (mean difference [MD]: 3.00, 95% confidence interval [CI]: 1.10-5.40, P = .03); the sensitivity analysis showed that the statistical model was still stable after sequentially eliminating each article. Compared with the control group, noninvasive cerebellar stimulation improved the 6MWT results of patients with stroke (MD: 25.29, 95% CI: 4.86-45.73, P = .02). However, noninvasive cerebellar stimulation did not improve the BI (MD: 15.61, 95% CI: -7.91 to 39.13, P = .19). No safety problems or adverse reactions to noninvasive cerebellar stimulation were observed. CONCLUSIONS: Noninvasive cerebellar stimulation improves balance and walking function of patients with stroke, but its effect on ADL is uncertain. Due to the methodological weaknesses in the included trials, more RCTs are needed to confirm our conclusions.

Spermidine levels are implicated in heavy metal tolerance in a spermidine synthase overexpressing transgenic European pear by exerting antioxidant activities.

To verify whether spermidine synthase (SPDS) can confer long-term multi-heavy metal tolerance, in vitro shoots of a transgenic European pear (Pyrus communis L. 'Ballad') line #32 overexpressing apple SPDS (MdSPDS1), as well as a wild type (WT) line, were subjected to stress using either CdCl(2), PbCl(2), ZnCl(2), or a combination thereof. Based on either shoot height increment or fresh weight and morphological changes upon heavy metal stress, the performance of the transgenic line #32 was better than that of WT. Although SPDS expression levels and spermidine (Spd) contents in line #32 were higher than those in WT, possibly due to transgene (MdSPDS1) expression, no obvious inductions of SPDS expression and increases in Spd-content were observed by long-term stress treatments in both lines. When the glutathione (GSH) content was compared with or without stress in each line, GSH was significantly depleted in line #32 with stress, but not as much as in WT. The activities of glutathione reductase and superoxide dismutase and the content of malondialdehyde, an indicator for lipid peroxidation, changed upon stress toward a more favorable status for survival in line #32 than in WT. These antioxidant parameters were positively related to Spd-content. The accumulation of heavy metals tended to be less in line #32 than in WT except for Zn stress, and the Ca content showed an opposite trend. These results suggest that Spd-levels are implicated in enhanced heavy metal tolerance, possibly by exerting an antioxidant activity as well as by the properties of Spd per se including metal chelator.

Association between a TCF4 Polymorphism and Susceptibility to Schizophrenia.

The basic helix-loop-helix (bHLH) transcription factor 4 (TCF4) had been identified as a susceptibility gene associated with schizophrenia (SCZ) by GWAS, but inconsistent results have been found in other studies. To validate these findings and to reveal the effects of different inheritance models, rs2958182, rs1261085, rs8766, and rs12966547 of the TCF4 gene were genotyped in the Northwest Han Chinese population (448 cases and 628 controls) via a multiplex polymerase chain reaction SNPscan assay. Single SNP, genotype, and association analyses with three different models were performed. We observed genotype and allele distributions of four SNPs that showed nonsignificant associations in the Northwest Han Chinese population. However, published datasets (51,892 cases and 68,498 controls) were collected and combined with our experimental results to ascertain the association of the TCF4 gene SNPs and SCZ, which demonstrated that rs2958182 (P=0.003) was a significant signal based on a systematic meta-analysis. To clarify the biological role of rs2958182, it is important to improve the understanding of the pathophysiology of SCZ.

Highly Selective and Sensitive Detection of Biogenic Defense Phytohormone Salicylic Acid in Living Cells and Plants Using a Novel and Viable Rhodamine-Functionalized Fluorescent Probe.

Detecting plant-derived signal molecules using fluorescent probes is a key topic and a huge challenge for scientists. Salicylic acid (SA), a vital plant-derived defense hormone, can activate global transcriptional reprogramming to systemically express a network of prominent pathogenesis-related proteins against invasive microorganisms. This strategy is called systemic acquired resistance (SAR). Therefore, monitoring the dynamic fluctuations of SA in subcellular microenvironments can advance our understanding of different physiological and pathological functions during the SA-induced SAR mechanism, thus benefiting the discovery and development of novel immune activators that contribute to crop protection. Here, detection of signaling molecule SA in plant callus tissues was first reported and conducted by a simple non-fluorescent rhodamine-tagged architecture bearing a flexible 2-amino-N,N-dimethylacetamide pattern. This study can markedly advance and promote the usage of fluorescent SA probes for distinguishing SA in the plant kingdom.

Molecular cloning and characterization of the light-harvesting chlorophyll a/b gene from the pigeon pea (Cajanus cajan).

Light-harvesting chlorophyll a/b-binding proteins (LHCB) have been implicated in the stress response. In this study, a gene encoding LHCB in the pigeon pea was cloned and characterized. Based on the sequence of a previously obtained 327 bp Est, a full-length 793 bp cDNA was cloned using the rapid amplification of cDNA ends (RACE) method. It was designated CcLHCB1 and encoded a 262 amino acid protein. The calculated molecular weight of the CcLHCB1 protein was 27.89 kDa, and the theoretical isoelectric point was 5.29. Homology search and sequence multi-alignment demonstrated that the CcLHCB1 protein sequence shared a high identity with LHCB from other plants. Bioinformatics analysis revealed that CcLHCB1 was a hydrophobic protein with three transmembrane domains. By fluorescent quantitative real-time polymerase chain reaction (PCR), CcLHCB1 mRNA transcripts were detectable in different tissues (leaf, stem, and root), with the highest level found in the leaf. The expression of CcLHCB1 mRNA in the leaves was up-regulated by drought stimulation and AM inoculation. Our results provide the basis for a better understanding of the molecular organization of LCHB and might be useful for understanding the interaction between plants and microbes in the future.

Association of the NOTCH4 Gene Polymorphism rs204993 with Schizophrenia in the Chinese Han Population.

NOTCH4 regulates signaling pathways associated with neuronal maturation, a process involved in the development and patterning of the central nervous system. The NOTCH4 gene has also been identified as a possible susceptibility gene for schizophrenia (SCZ). The objective of this study was to examine the relationship between NOTCH4 polymorphisms and SCZ in the Chinese Han population. The rs2071287 and rs204993 polymorphisms of the NOTCH4 gene were analyzed in 443 patients with SCZ and 628 controls of Han Chinese descent. Single SNP allele-, genotype-, and gender-specific associations were analyzed using different models (i.e., additive, dominant, and recessive models). This association study revealed that the rs204993 polymorphism is significantly associated with susceptibility for SCZ and that the AA genotype of rs204993 is associated with a higher risk for SCZ (P = 0.027; OR = 1.460; 95% CI, 1.043-2.054). Our data are consistent with those obtained in previous studies that suggested that rs204993 is associated with SCZ and that the AA genotype of rs204993 demonstrates a higher risk. Further large-scale association analyses in Han Chinese populations are warranted.

Isolation and characterization of a catalase gene "HuCAT3" from pitaya (Hylocereus undatus) and its expression under abiotic stress.

Abiotic stresses usually cause H2O2 accumulation, with harmful effects, in plants. Catalase may play a key protective role in plant cells by detoxifying this excess H2O2. Pitaya (Hylocereus undatus) shows broad ecological adaptation due to its high tolerance to abiotic stresses, e.g. drought, heat and poor soil. However, involvement of the pitaya catalase gene (HuCAT) in tolerance to abiotic stresses is unknown. In the present study, a full-length HuCAT3 cDNA (1870 bp) was isolated from pitaya based on our previous microarray data and RACE method. The cDNA sequence and deduced amino acid sequence shared 73-77% and 75-80% identity with other plant catalases, respectively. HuCAT3 contains conserved catalase family domain and catalytic sites. Pairwise comparison and phylogenetic analysis indicated that HuCAT3 is most similar to Eriobotrya japonica CAT, followed by Dimocarpus longan CAT and Nicotiana tabacum CAT1. Expression profile analysis demonstrated that HuCAT3 is mainly expressed in green cotyledons and mature stems, and was regulated by H2O2, drought, cold and salt stress, whereas, its expression patterns and maximum expression levels varied with stress types. HuCAT activity increased as exposure to the tested stresses, and the fluctuation of HuCAT activity was consistent with HuCAT3 mRNA abundance (except for 0.5 days upon drought stress). HuCAT3 mRNA elevations and HuCAT activities changes under cold stress were also in conformity with the cold tolerances among the four genotypes. The obtained results confirmed a major role of HuCAT3 in abiotic stress response of pitaya. This may prove useful in understanding pitaya's high tolerance to abiotic stresses at molecular level.

Genetic and epigenetic evaluations of citrus calluses recovered from slow-growth culture.

The embryogenic callus of "Red Marsh" grapefruit was stored in vitro by slow growth culture method for one year, and survived with a significant weight increment over that period. The survivers regenerated somatic embryos more easily than the controls. Eight callus lines were used for genetic analyses. Although chromosome number variations were verified by cytological examination both in the controls and the stored samples, the ploidy level remained relatively stable during the storage period. Randomly amplified polymorphic DNA (RAPD) analysis was performed to detect DNA sequence variation. No difference in RAPD pattern was found with the 102 primers used. However, a methylation sensitive amplified polymorphism (MSAP) assay showed DNA methylation changes in the stored samples compared with the controls.

Identification of differentially-expressed genes potentially implicated in drought response in pitaya (Hylocereus undatus) by suppression subtractive hybridization and cDNA microarray analysis.

Drought is one of the most severe threats to the growth, development and yield of plant. In order to unravel the molecular basis underlying the high tolerance of pitaya (Hylocereus undatus) to drought stress, suppression subtractive hybridization (SSH) and cDNA microarray approaches were firstly combined to identify the potential important or novel genes involved in the plant responses to drought stress. The forward (drought over drought-free) and reverse (drought-free over drought) suppression subtractive cDNA libraries were constructed using in vitro shoots of cultivar 'Zihonglong' exposed to drought stress and drought-free (control). A total of 2112 clones, among which half were from either forward or reverse SSH library, were randomly picked up to construct a pitaya cDNA microarray. Microarray analysis was carried out to verify the expression fluctuations of this set of clones upon drought treatment compared with the controls. A total of 309 expressed sequence tags (ESTs), 153 from forward library and 156 from reverse library, were obtained, and 138 unique ESTs were identified after sequencing by clustering and blast analyses, which included genes that had been previously reported as responsive to water stress as well as some functionally unknown genes. Thirty six genes were mapped to 47 KEGG pathways, including carbohydrate metabolism, lipid metabolism, energy metabolism, nucleotide metabolism, and amino acid metabolism of pitaya. Expression analysis of the selected ESTs by reverse transcriptase polymerase chain reaction (RT-PCR) corroborated the results of differential screening. Moreover, time-course expression patterns of these selected ESTs further confirmed that they were closely responsive to drought treatment. Among the differentially expressed genes (DEGs), many are related to stress tolerances including drought tolerance. Thereby, the mechanism of drought tolerance of this pitaya genotype is a very complex physiological and biochemical process, in which multiple metabolism pathways and many genes were implicated. The data gained herein provide an insight into the mechanism underlying the drought stress tolerance of pitaya, as well as may facilitate the screening of candidate genes for drought tolerance.

Video-assisted thoracic surgery right upper lobectomy and lymph node dissection.

We described a 55-year-old male smoking patient, who came to our institute with the diagnosis of a right upper lobe lesion. Computed tomographic (CT) guided biopsy confirmed a diagnosis of lung adenocarcinoma. The preoperative clinical diagnosis was stage I primary lung adenocarcinoma. The standard three-port video-assisted thoracoscopy surgery (VATS) was performed in this case. After the resection of the right upper lobe, the 2(nd), 4(th), and 7(th) groups of lymphatic nodes were removed with Harmonic scalpel. A closed drainage catheter was placed adjacent to the lateral chest wall through the port in the 7th intercostal space. Postoperative pathologic diagnosis was T2aN0M0 adenocarcinoma.

Molecular cloning and expression analysis of an arginine decarboxylase gene from peach (Prunus persica).

Arginine decarboxylase (ADC), one of the enzymes responsible for putrescine (Put) biosynthesis, has been shown to be implicated in stress response. In the current paper attempts were made to clone and characterize a gene encoding ADC from peach (Prunus persica (L.) Batsch, 'Akatsuki'). Rapid amplification of cDNA ends (RACE) gave rise to a full-length ADC cDNA (PpADC) with a complete open reading frame of 2178 bp, encoding a 725 amino acid polypeptide. Homology search and sequence multi-alignment demonstrated that the deduced PpADC protein sequence shared a high identity with ADCs from other plants, including several highly conservative motifs and amino acids. Southern blotting indicated that PpADC existed in peach genome as a single gene. Expression levels of PpADC in different tissues of peach (P. persica 'Akatsuki') were spatially and developmentally regulated. Treatment of peach shoots from 'Mochizuki' with exogenous 5 mM Put, an indirect product of ADC, remarkably induced accumulation of PpADC mRNA. Transcripts of PpADC in peach leaves from 'Mochizuki' were quickly induced, either transiently or continuously, in response to dehydration, high salinity (200 mM NaCl), low temperature (4 degrees C) and heavy metal (150 microM CdCl(2)), but repressed by high temperature 37 degrees C) during a 2-day treatment, which changed in an opposite direction when the stresses were otherwise removed with the exception of CdCl(2) treatment. In addition, steady-state of PpADC mRNA could be also transiently up-regulated by abscisic acid (ABA) in 'Mochizuki' leaves. All of these, taken together, suggest that PpADC is a stress-responsive gene and can be considered as a potential target that is genetically manipulated so as to create novel germplasms with enhanced stress tolerance in the future.

Over-expression of the apple spermidine synthase gene in pear confers multiple abiotic stress tolerance by altering polyamine titers.

An apple spermidine synthase (SPDS) gene (MdSPDS1) was verified to encode a functional protein by the complementation of the spe3 yeast mutant, which lacks the SPDS gene. To justify our hypothesis that apple SPDS is involved in abiotic stress responses and to obtain transgenic fruit trees tolerant to abiotic stresses as well, MdSPDS1-over-expressing transgenic European pear (Pyrus communis L. 'Ballad') plants were created by Agrobacterium-mediated transformation. A total of 21 transgenic lines showing various spermidine (Spd) titers and MdSPDS1 expression levels were obtained. Selected lines were exposed to salt (150 mM NaCl), osmosis (300 mM mannitol), and heavy metal (500 microM CuSO4) stresses for evaluating their stress tolerances. Transgenic line no. 32, which was revealed to have the highest Spd accumulation and expression level of MdSPDS1, showed the strongest tolerance to these stresses. When growth increments, electrolyte leakage (EL), and values of thiobarbituric acid reactive substances (TBARS) were monitored, line no. 32 showed the lowest growth inhibition and the least increase in EL or TBARS under stress conditions. Spd titers in wild-type and transgenic lines showed diverse changes upon stresses, and these changes were not consistent with the changes in MdSPDS1 expressions. Moreover, there were no differences in the sodium concentration in the shoots between the wild type and line no. 32, whereas the copper concentration was higher in the wild type than in line no. 32. Although the mechanism(s) underlying the involvement of polyamines in stress responses is not known, these results suggest that the over-expression of the SPDS gene substantially increased the tolerance to multiple stresses by altering the polyamine titers in pear. Thus, MdSPDS1-over-expressing transgenic pear plants could be used to improve desert land and/or to repair polluted environments.

[Expression and Significance of BP1 Gene and Cyclin D1 Gene in Breast Cancer].

BACKGROUND & OBJECTIVE: BP1, a novel transcriptional factor, belongs to DLX family of homeobox genes. Recent researches showed that BP1 gene is correlated to genesis of breast cancer, but its correlation to cell cycle control factor has not been reported yet. This study was to observe the expression of BP1 in breast cancer, and to make clear its correlation to Cyclin D1. METHODS: The expression of BP1 and Cyclin D1 in 86 specimens of human breast cancer and 20 specimens of normal breast tissue (3 cm away from primary tumor) was detected by reverse transcription-polymerase chain reaction (RT-PCR). BP1 poly antibody was made and was certificated by Western blot. The expression of BP1 and Cyclin D1 in 86 specimens of human breast cancer were detected by immunohistochemistry; their correlation was analyzed. RESULTS: The positive rate of BP1 mRNA was significanlty higher in breast cancer than in normal breast tissues (69.8% vs. 0, P < 0.001). The positive rate of Cyclin D1 mRNA was 64.0% in breast cancer. BP1 mRNA and Cyclin D1 mRNA were co-expressed in 52 specimens of breast cancer, and simultaneously negative in 23 specimens (P = 0.227); BP1 protein and Cyclin D1 protein were co-expressed in 43 specimens, and simultaneously negative in 31 specimens (P = 0.146). CONCLUSIONS: BP1 gene is highly expressed in breast cancer. There is co-expression of Cyclin D1 and BP1 in breast cancer. BP1 gene may promote the genesis of breast cancer through regulating the expression of Cyclin D1.

Polyamine biosynthesis of apple callus under salt stress: importance of the arginine decarboxylase pathway in stress response.

To clarify the involvement of the arginine decarboxylase (ADC) pathway in the salt stress response, the polyamine titre, putrescine biosynthetic gene expression, and enzyme activities were investigated in apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] in vitro callus under salt stress, during recovery after stress, and when ADC was inhibited by D-arginine, an inhibitor of ADC. Salt stress (200 mM NaCl) caused an increase in thiobarbituric acid-reactive substances (TBARS) and electrolyte leakage (EL) of the callus, which was accompanied by an increase in free putrescine content, during 7 d of treatment. Conjugated putrescine was also increased, but this increase was limited to the early stage of salt stress. Accumulation of putrescine was in accordance with induction of ADC activity and expression of the apple ADC gene (MdADC). When callus that had been treated with 200 mM NaCl was transferred to fresh medium with (successive stress) or without (recovery) NaCl, TBARS and EL were significantly reduced in the recovery treatment, indicating promotion of formation of new callus cells, compared with the successive stress treatment. Meanwhile, MdADC expression and ADC activity were also decreased in the callus undergoing recovery, whereas those of the callus under successive stress were increased. Ornithine decarboxylase (ODC) activity showed a pattern opposite to that of ADC in these conditions. D-Arginine treatment led to more serious growth impairment than no treatment under salt stress. In addition, accumulation of putrescine, induction of MdADC, and activation of ADC in D-arginine-treated callus were not comparable with those of the untreated callus. Exogenous addition of putrescine could alleviate salt stress in terms of fresh weight increase and EL. All of these findings indicated that the ADC pathway was tightly involved in the salt stress response. Accumulation of putrescine under salt stress, the possible physiological role of putrescine in alleviating stress damage, and involvement of MdADC and ADC in response to salt stress are discussed.