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Deoxyribonucleic acid (DNA) methylation plays an important role in fruit ripening and senescence. Here, the role of DNA methylation of the CpG island of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 genes induced by heat treatment (37 °C) in postharvest ripening of tomato fruit was studied. After heat treatment, the firmness and vitamin C content showed higher levels, the loss of aldehydes in volatile components was delayed, and the activities of methylase and demethylase decreased in tomato fruit. Moreover, in heat-treated fruit, significant changes in DNA methylation of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 were induced, the expression of LeERT10 and LeEIN3 was inhibited, the expression of SlERF-A1 was increased, by which ethylene signal transmission might be suppressed and the postharvest ripening of tomato fruit was delayed. The present study provided valuable information for understanding the essential role of DNA methylation in the postharvest ripening of tomato fruit.

The effect of 1-methylcyclopropene (1-MCP) on inhibiting postharvest blue mold of apple fruit caused by Penicillium expansum and suppressing the growth of P. expansum in vitro was investigated. The treatment of 5 μL L −1 1-MCP significantly decreased disease severity of apple fruit caused by P. expansum and suppressed the mycelial growth and spore germination of P. expansum . After treatment with 1-MCP, lower integrity of plasma membrane in the spores of P. expansum was detected, higher levels of reactive oxygen species (ROS) in the spores and malondialdehyde (MDA) in the mycelium was observed, indicating that 1-MCP treatment enhanced oxidative damage to P. expansum and destroyed the integrity of plasma membrane of spores. This study for the first time demonstrated that 1-MCP suppressed postharvest blue mold of apple fruit by inhibiting the growth of P. expansum .

Anthracnose caused by Colletotrichum gloeosporioides is one of the most important postharvest diseases in mango fruit, often causing huge economic losses. In this study, the effect of 1-methylcyclopropene (1-MCP) against anthracnose in postharvest mango fruit and the mechanisms involved were investigated. 1-MCP induced reactive oxygen species (ROS) generation, damaged the mitochondria and destroyed the integrity of plasma membrane of spores of C. gloeosporioides, significantly suppressing spore germination and mycelial growth of C. gloeosporioides. 1-MCP also decreased the decay incidence and lesion expansion of mango fruit caused by C. gloeosporioides. For the first time this study demonstrated that 1-MCP suppressed anthracnose of postharvest mango fruit by directly inhibiting spore germination and mycelial growth of C. gloeosporioides, thus providing a promising strategy for disease control.

To understand the microRNAs (miRNAs)-mediated mechanism of low temperature delaying non-climacteric strawberry fruit senescence during postharvest period, two small RNA (sRNA) libraries from strawberry fruit stored at low temperature for 24 and 48 h were constructed. A total of 88 known and 1224 novel potential candidate miRNAs were obtained and analyzed. Compared with the expression of miRNAs in strawberry fruit stored for 0 h, 108 miRNAs were up-regulated and 113 were down-regulated in fruit stored at 24 h, and 139 miRNAs were up-regulated and 114 were down-regulated in fruit stored at 48 h. In the process of fruit storage under low temperature, PC-5p-176409_20 repressed abscisic acid (ABA) signaling transduction via the PYR1/PYL1-PP2C-SnRK2 network, miR167 reduced the jasmonic acid (JA) biosynthesis by targeting auxin response factor 8(ARF8), and by which they were involved in delaying fruit senescence. MiR164, miR172, PC-5p-67794_53 and PC-5p-1004_3092 up- or down-regulated the expression of their target genes, NAC transcription factors, APETALA2.7 (AP2.7) transcription factor, alpha/beta-hydrolases superfamily protein and glycosyl hydrolase 9B1, respectively, and also involved in delaying fruit senescence under low temperature. These results give valuable information for understanding the role of miRNA in mediating the fruit senescence at low temperature.

One novel transcription factor gene DnWRKY29 was isolated from Dendrobium officinale, and its functions were identified by its overexpression in tobacco. Compared to the wild type (WT), the DnWRKY29 transgenic tobacco seeds and seedlings showed more sensitivity to salt and drought stresses. The seed germination rate, seedling root length, and fresh weight of transgenic tobacco were lower than in WT. The activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in transgenic tobacco were decreased, and the content of malondialdehyde (MDA) in transgenic tobacco was increased. Moreover, the expression of DnWRKY29 was up-regulated in Dendrobium seedlings under salt and drought stresses, which was consistent with the function identified by its overexpression in tobacco, indicating that the up-regulation or overexpression of DnWRKY29 impaired plant tolerance to salt and drought stresses. These results provided a new insight to the low tolerance of Dendrobium seedlings to environmental change.

Proton (H+) and aluminum (Al3+) toxicities are major factors limiting crop production on acid soils. To study whether salicylic acid (SA) is functional in alleviating protein damage caused by H+ and Al3+ toxicities, an investigation of the antioxidant defense response regulated by SA was carried out on barley (Hordeum vulgare L.) seedlings under H+, Al3+, and combined stresses. It was found that the relative root elongation of seedlings, which grew in the solutions supplemented with SA, was significantly higher than that of seedlings without SA treatment after 24-h treatments with H+, Al3+, and combined stresses. The lesser amount of carbonylated proteins with molecular weights ranging from 14.4 to 97 kD, was accumulated in seedlings treated with SA than that in the seedlings without SA treatment. The higher activities of antioxidant enzymes and lesser content of MDA were observed in seedlings treated with SA compared with the seedlings without SA treatment. Moreover, the nitroblue tetrazolium staining of roots showed that ROS accumulation was decreased by SA treatments. This study suggested that SA could alleviate cell damage caused by H+ and Al3+ toxicities on acid soils by both activating antioxidant defense responses and reducing the contents of carbonylated proteins caused by ROS in barley seedlings.

BACKGROUND: Proton (H+) and aluminium (Al3+) toxicities are major factors limiting crop production on acid soils, while γ-aminobutyric acid (GABA) is a non-protein amino acid involved in various stress tolerances in plants. In this study, to determine whether exogenous GABA is functional in alleviating oxidative stress induced by H+ and Al3+ toxicities, the antioxidant defence response regulated by GABA was investigated in barley (Hordeum vulgare L.). RESULTS: After 24 h treatments of seedlings under H+, Al3+ and combined stresses with and without GABA, morphological and biochemical assays were conducted. It was observed that the inhibition of seedling root elongation caused by Al3+ and H+ toxicities was significantly mitigated by GABA. The amount of carbonylated proteins with molecular masses of 14.4–97 kDa was decreased. The activities of antioxidant enzymes were enhanced, the content of malondialdehyde was reduced and the accumulation of reactive oxygen species (ROS), as shown by staining roots with nitroblue tetrazolium, declined in GABA-treated seedlings. CONCLUSION: GABA can alleviate oxidative damage caused by H+ and Al3+ toxicities in barley seedlings by activating antioxidant defence responses and reducing the elevated levels of carbonylated proteins caused by ROS. Copyright © 2010 Society of Chemical Industry

Three AtHSP90 isoforms, cytosol-localized AtHSP90.2, chloroplast-localized AtHSP90.5, and endoplasmic reticulum (ER)-localized AtHSP90.7 genes, were constitutively overexpressed in Arabidopsis thaliana to study their functional mechanisms under oxidative stress. Overexpression of AtHSP90 genes reduced germination of transgenic seeds under oxidative stress. When exposed to 10 mM H2O2, AtHSP90 transgenic seedlings displayed lower activities of superoxide dismutase, catalase, and peroxidase; higher content of malondialdehyde; and higher levels of protein damage than detected in the wild type. This indicated that overexpression of AtHSP90.2, AtHSP90.5, and AtHSP90.7 in Arabidopsis impaired plant tolerance to oxidative stress. Moreover, overexpression of chloroplast- and ER-localized AtHSP90 resulted in lower resistance to oxidative stress than that of cytosolic AtHSP90. This suggested that HSP90.2, HSP90.5, and HSP90.7 localized in different cellular compartments were involved in different functional mechanisms during oxidative stress.

The functions of cytosolic heat shock protein AtHsp90.3 in response to heavy metal stress were characterized by using expression of AtHsp90.3 gene in yeast and Arabidopsis thaliana. AtHsp90.3 supported the Saccharomyces cerevisiae Hsp90 knockout strain R0005 growth and maintaining cells membrane integrity under cadmium and arsenic stresses, which was compatible with the components of ScHsc82 machinery. However, constitutive overexpression of AtHsp90.3 in Arabidopsis impaired plant tolerance to Cd stress with lower germination rate and shorter root length, decreased contents of phytochelatins (PCs) and glutathione (GSH), inhibited activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), and increased content of malondialdehyde (MDA). These results suggested that proper homeostasis of Hsp90 was critical for cellular response and/or tolerance to heavy metal stress in plants.

Salvia miltiorrhiza is one of the most popular traditional medicinal herbs in Asian nations. Its dried root contains a number of tanshinones, protocatechuic aldehyde, salvianolic acid B and rosmarinic, and is used for the treatment of various diseases. The finding of microRNAs (miRNAs) and their target genes will help understand their biological role on the biosynthesis of tanshinones in S. miltiorrhiza. In the present study, a total of 452 known miRNAs corresponding to 589 precursor miRNAs (pre-miRNAs), and 40 novel miRNAs corresponding to 24 pre-miRNAs were identified in different tissues of S. miltiorrhiza by high-throughput sequencing, respectively. Among them, 62 miRNAs express only in root, 95 miRNAs express only in stem, 19 miRNAs express only in leaf, and 71 miRNAs express only in flower, respectively. By the degradome analysis, 69 targets potentially cleaved by 25 miRNAs were identified. Among them, acetyl-CoA C-acetyltransferase was cleaved by miR5072, and involved in the biosynthesis of tanshinones. This study provided valuable information for understanding the tissue-specific expression patterns of miRNAs in S. miltiorrhiza, and offered a foundation for future studies of the miRNA-mediated biosynthesis of tanshinones.

A 1681 bp PsPR10 promoter was isolated from Pinus strobus and a series of 5′-deletions were fused to the β-glucuronidase (GUS) reporter gene and introduced into tobacco. GUS activity in P796 (−796 to +69) construct transgenic plant roots was similar with that of P1681 and higher than those of the P513 (−513 to +69) and P323 (−323 to +69) transgenic plants. Moreover, the abiotic stresses of NaCl, PEG 6000 and mannitol, and salicylic acid (SA), abscisic acid (ABA) and jasmonic acid (JA) induced higher GUS activity in the roots of P796 transgenic tobacco. This study provides a potential inducible root-specific promoter for transgenic plants.