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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 melatonin on chilling injury of banana fruit was investigated. Results showed that melatonin treatment delayed chilling injury and alleviated peel browning. Melatonin treatment increased the contents of phospholipids and unsaturated fatty acid, induced the reactive oxygen species (ROS) scavenging enzyme activities, and reduced the contents of H2O2, O2– of banana fruit. It also induced the miR528 expression, resulting in the down expression of the potential target genes of MaPPO1, MaPPO2 and MaPPO3, and inhibited the PPO activities. Moreover, the phenolic compounds in melatonin treated banana fruit peel were quantitatively analyzed by liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results indicated that melatonin treatment changed the contents of 63 polyphenolics in banana fruit, and by which involved in delaying chilling injury and alleviating peel browning. In conclusion, melatonin treatment is a potential technique in alleviating chilling injury of banana fruit under low temperature storage.

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 .

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.

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, cytosolic AtHsp90.2, chloroplast-located AtHsp90.5, and endoplasmic reticulum (ER)-located AtHsp90.7, were characterized by constitutive overexpressing their genes in Arabidopsis thaliana. Both types of the transgenic plants overexpressing cytosolic and organellar AtHsp90s showed reduced tolerance to salt and drought stresses with lower germination rates and fresh weights, but improved tolerance to high concentration of Ca(2+) comparing with the wild type plants. Transcriptional analysis of ABA-responsive genes, RD29A, RD22 and KIN2 under salt and drought stresses, indicated that the induction expression of these genes was delayed by constitutive overexpression of cytosolic AtHsp90.2, but was hardly affected by that of organellar AtHsp90.5 and AtHsp90.7. These results implied that Arabidopsis different cellular compartments-located Hsp90s in Arabidopsis might be involved in abiotic stresses by different functional mechanisms, probably through ABA-dependent or Ca(2+) pathways, and proper homeostasis of Hsp90 was critical for cellular stress response and/or tolerance in plants.

In non-climacteric fruits, the respiratory increase is absent and no phytohormone is appearing to be critical for their ripening process. They must remain on the parent plant to enable full ripening and be picked at or near the fully ripe stage to obtain the best eating quality. However, huge losses often occur for their quick post-harvest senescence. To understanding the complex mechanism of non-climacteric fruits post-harvest senescence, we constructed two small RNA libraries and one degradome from strawberry fruit stored at 20°C for 0 and 24 h. A total of 88 known and 1224 new candidate miRNAs, and 103 targets cleaved by 19 known miRNAs families and 55 new candidatemiRNAs were obtained. These targets were associated with development, metabolism, defense response, signaling transduction and transcriptional regulation. Among them, 14 targets, including NAC transcription factor, Auxin response factors (ARF) and Myb transcription factors, cleaved by 6 known miRNA families and 6 predicted candidates, were found to be involved in regulating fruit senescence. The present study provided valuable information for understanding the quick senescence of strawberry fruit, and offered a foundation for studying the miRNA-mediated senescence of non-climacteric fruits.

Rice seed size is an important agronomic trait in determining the yield potential, and four seed size related genes (GS3, GW2, qSW5/GW5 and GIF1) have been cloned in rice so far. However, the relationship among these four genes is still unclear, which will impede the process of gene pyramiding breeding program to some extent. To shade light on the relationship of above four genes, gene expression analysis was performed with GS3-RNAi, GW2-RNAi lines and CSSL of qSW5 at the transcriptional level. The results clearly showed that qSW5 and GW2 positively regulate the expression of GS3. Meanwhile, qSW5 can be down-regulated by repression of GW2 transcription. Additionally, GIF1 expression was found to be positively regulated by qSW5 but negatively by GW2 and GS3. Moreover, the allelic effects of qSW5 and GS3 were detailedly characterized based on a natural population consisting of 180 rice cultivars. It was indicated that mutual interactions exist between the two genes, in which, qSW5 affecting seed length is masked by GS3 alleles, and GS3 affecting seed width is masked by qSW5 alleles. These findings provide more insights into the molecular mechanisms underlying seed size development in rice and are likely to be useful for improving rice grain yield.

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.