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  • Author or Editor: Tingting Chen x
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The goal of this study was isolate genes that are regulated by Al treatments of tomato roots growing in vitro. For Al treatment, germinating tomato seeds were plated on a MS agar medium supplemented with 0, 350, and 1200 μM AlCl3 for 30 days. Total RNA was extracted from root tissues and separated on denature formamide gel to check their quantity and quality. Equal amount of total RNA from treatment and control was treated with DNAse I (Genhunter, TN) to remove genomic DNA contamination. cDNA was obtained by reverse transcription using all the regents in RNA Image Kit (Genhunter, TN). The cDNA was amplified using the fluorescently labeled anchor primers (Oligo dT-A, C, G) and 16 random primers. Amplification products were separated by electrophoresis in 6% nondenaturing polyacrylamide gels and DNA bands were observed by scanning the gel on a FMBIOIII scanner. After comparing the band profile on the gel image, fragments of gene that showed changes in intensity compared to control (0 μM AlCl3) were isolated from the gel manually. These bands were re-amplified with the same pair of primers as the original amplification and cloned onto PCR-Trap cloning vector (Genhunter, TN). After DNA sequence analysis and homology comparison with NCBI database, we have identified clone # C01HBa0256E08 on L. esculentum chromosome 01, clone # C10HBa0111D09 on chromosome 10 and clone # LE_HBa-31H5 on chromosome 4.

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Photorespiration provides a protection mechanism in plants by diverting excessive energy accumulated from photochemical reaction, metabolizing toxic products and producing some protective molecules. The authors report cloning and characterization of a glycolate oxidase gene (GOX; NCBI accession DQ442286) and a NADH-dependent hydroxypyruvate reductase gene (HPR; NCBI DQ442287) from Pachysandra terminallis. The DQ442286 had the predicted GOX-like–Riboflavin-5′-phosphate (FMN) conserved domain and the DQ442287 had the predicted adenosine 5′-(alpha-thio)diphospho-5′-ribofuranosylnicotinamide nicotinamide adenine dinucleotide (NAD) binding domain (2-Hacid_DH_C). C-terminal peroxisome targeting signal was predicted to be -ARL for DQ442286 and –SKL for DQ442287. Both genes encoded enzyme proteins that are located in peroxisome and are involved in the photorespiration process. Real-time quantitative reverse-transcriptase polymerase chain reaction was performed to compare transcript level of the cloned genes after cold treatment. The 18s Ribosomal RNA (rRNA) was included to calibrate the data. The relative cycle threshold values (gene/18s rRNA) were 1.4, 1.5, and 1.5 for GOX and 1.2, 1.3, and 1.3 for HPR in the treatments of 4 °C 4 h, 4 °C 12 h, and control. The data revealed that gene expression was enhanced by only short-term (4-h) cold treatment. A ribulose-1, 5-biphosphate carboxylase/oxygenase (Rubisco) activase gene (DQ 486905) was also cloned and analyzed following the same procedure.

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Identification of low temperature–regulated gene expression in Pachysandra terminalis: Pachysandra terminalis is a cold-hardy, evergreen plant species. In order to identify molecular mechanism of cold tolerance of this plant species, seedlings with four fully expanded leaves were subjected to 4, 0, and –1 °C low temperature treatments. Low temperature–induced genes were identified from treated plants using cDNA differential display. The cDNA fragments were cloned onto PCR-trap vectors. Low temperature regulation of these genes was confirmed by reverse-northern blot. Sequence analysis has identified that these genes can be classified into three groups, stress-related, photosystem-related. Most of the genes cannot find matching sequences in the database. To further study the regulation of these genes by temperature fluctuation, the plants were treated at 4, 0, and 40 °C. Northern blot analysis showed that several clones showed increased expression after cold and heat shock. Previous cold treatment at 4 °C can negate the effect of heat shock on expression of these genes. Complete sequence of these genes is cloned from the cDNA library and their temporal regulation by environmental stresses is analyzed using real-time PCR.

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Centipedegrass [Eremochloa ophiuroides (Munro) Hack] is a native grass of China, and information on soil adaptation ranges, including acid soils, among centipedegrass cultivars is limited. Therefore, objectives of this study were 1) to conduct a preliminary evaluation of relative aluminum tolerance of 48 centipedegrass accessions plus a cultivar, TifBlair, and a common centipedegrass under aluminum (Al) stress (0 and 1500 μM Al) by using a solution culture method; and 2) to determine Al effects on nutrient uptake between resistant-group and sensitive-group accessions among the 50 accessions and cultivars. Differences were found among accessions and cultivars, and the CV of relative root weight, relative shoot weight, and relative total weight were 39.9%, 32.9%, and 33.6%, respectively. After growing 28 days in an acid subsoil, the resistant-group accessions showed much better growth than the sensitive-group accessions. The Al concentrations in roots and shoots of the two groups of accessions were increased under Al treatment, but most absorbed Al remained in roots with greater Al absorption among the sensitive group compared with the resistant group. The concentrations of phosphorus (P), magnesium (Mg), calcium (Ca), and potassium (K) in the two groups were reduced under Al stress with reductions of 59.3%, 54.8%, 47.9%, and 41.3% in shoots and reductions of 8.70%, 52.5%, 43.2%, and 34.4% in roots, respectively. Under Al stress, differences in P, Mg, and Ca concentrations were found between the two groups; however, differences were not found for K. The resistant-group accessions maintained higher concentrations of Mg and Ca than the sensitive group.

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Kiwifruit (Actinidia chinensis Planchon) is an economically important fruit, and its flowering and production are affected by the chill accumulation in winter. In this study, the chilling requirements of nine kiwifruit cultivars with three ploidy levels (diploid, tetraploid, and hexaploid) were analyzed by using the Dynamic Model, Utah Model, and chilling hours (CH) Model. The chilling requirements for vegetative budbreak of these kiwifruit cultivars were 24–55 chill portions (CP), 316–991 chill units (CU), and 222–853 CH, and the chilling requirements for floral emergence were 45–69 CP, 825–1336 CU, and 655–1138 CH. The chilling requirements for vegetative budbreak and floral emergence were significantly lower for diploid than hexaploid cultivars with tetraploid cultivars intermediate. Pearson correlation analysis indicated that ploidy levels were positively correlated with chilling requirement, with the cv of 0.74 and 0.82 for vegetative budbreak and floral emergence chilling requirements, respectively. In conclusion, these results provide some novel insights of kiwifruit varieties of various chilling requirements, which is beneficial for kiwifruit cultivar selection for different climates and environments.

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Kiwifruit (Actinidia deliciosa) is a typical climacteric fruit, and its ripening is closely associated with ethylene. In this study, we present evidence that H2S alleviated ethylene-induced ripening and senescence of kiwifruit. Kiwifruit were fumigated with ethylene released from 0.4 g·L−1 ethephon solution or H2S with 1 mm sodium hydrosulfide (NaHS) as the donor or in combination. Fumigation with ethylene was found to accelerate kiwifruit ripening and H2S treatment effectively alleviated ethylene-induced fruit softening in parallel with attenuated activity of polygalacturonase (PG) and amylase. Ethylene + H2S treatment also maintained higher levels of ascorbic acid, titratable acid, starch, soluble protein, and reducing sugar compared with ethylene group, whereas suppressed the increase in chlorophyll and carotenoid. Kiwifruit ripening and senescence under ethylene treatment was accompanied by elevation in reactive oxygen species (ROS) levels, including H2O2 and superoxide anion and malondialdehyde (MDA), but combined treatment of ethylene plus H2S alleviated oxidative stress in fruit. Furthermore, the activities of antioxidative enzymes catalase (CAT) and ascorbate peroxidase (APX) were increased by ethylene + H2S treatment in comparison with ethylene alone, whereas the activities of lipoxygenase (LOX) and polyphenol oxidase (PPO) were attenuated by H2S treatment. Further investigations showed that H2S repressed the expression of ethylene synthesis-related genes AdSAM, AdACS1, AdACS2, AdACO2, and AdACO3 and cysteine protease genes, such as AdCP1 and AdCP3. Taken together, our findings suggest that H2S alleviates kiwifruit ripening and senescence by antagonizing the effect of ethylene through reduction of oxidative stress and inhibition of ethylene synthesis pathway.

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Zinc finger-homeodomains (ZF-HDs) are considered transcription factors that are involved in a variety of life activities in plants, but their function in regulating plant salt stress tolerance is unclear. The SL-ZH13 gene is significantly upregulated under salt stress treatment in tomato (Solanum lycopersicum) leaves, per our previous study. In this study, to further understand the role that the SL-ZH13 gene played in the response process of tomato plants under salt stress, the virus-induced gene silencing (VIGS) method was applied to down-regulate SL-ZH13 expression in tomato plants, and these plants were treated with salt stress to analyze the changes in salt tolerance. The silencing efficiency of SL-ZH13 was confirmed by quantitative real-time PCR analysis. SL-ZH13-silenced plants wilted faster and sooner than control plants under the same salt stress treatment condition, and the main stem bending angle of SL-ZH13-silenced plants was smaller than that of control plants. Physiological analysis showed that the activities of superoxide dismutase, peroxidase, and proline content in SL-ZH13-silenced plants were lower than those in control plants at 1.5 and 3 hours after salt stress treatment. The malondialdehyde content of SL-ZH13-silenced plants was higher than that in control plants at 1.5 and 3 hours after salt stress treatment; H2O2 and O2 - accumulated much more in leaves of SL-ZH13-silenced plants than in leaves of control plants. These results suggested that silencing of the SL-ZH13 gene affected the response of tomato plants to salt stress and decreased the salt stress tolerance of tomato plants.

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