Differences in drought stress tolerance within diverse rice genotypes have been attributed to genetic diversity and epigenetic alterations. DNA methylation is an important epigenetic modification that influences diverse biological processes, but its effects on rice drought stress tolerance are poorly understood. In this study, methylated DNA immunoprecipitation sequencing and an Affymetrix GeneChip rice genome array were used to profile the DNA methylation patterns and transcriptomes of the drought-tolerant introgression line DK151 and its drought-sensitive recurrent parent IR64 under drought and control conditions. The introgression of donor genomic DNA induced genome-wide DNA methylation changes in DK151 plants. A total of 1190 differentially methylated regions (DMRs) were detected between the two genotypes under normal growth conditions, and the DMR-associated genes in DK151 plants were mainly related to stress response, programmed cell death, and nutrient reservoir activity, which are implicated to constitutive drought stress tolerance. A comparison of the DNA methylation changes in the two genotypes under drought conditions indicated that DK151 plants have a more stable methylome, with only 92 drought-induced DMRs, than IR64 plants with 506 DMRs. Gene ontology analyses of the DMR-associated genes in drought-stressed plants revealed that changes to the DNA methylation status of genotype-specific genes are associated with the epigenetic regulation of drought stress responses. Transcriptome analysis further helped to identify a set of 12 and 23 DMR-associated genes that were differentially expressed in DK151 and IR64, respectively, under drought stress compared with respective controls. Correlation analysis indicated that DNA methylation has various effects on gene expression, implying that it affects gene expression directly or indirectly through diverse regulatory pathways. Our results indicate that drought-induced alterations to DNA methylation may influence an epigenetic mechanism that regulates the expression of unique genes responsible for drought stress tolerance.

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The purpose of the present study was to study the effects of resveratrol on cognitive function in rats with vascular dementia and to investigate the molecular mechanisms of its neuroprotective effects. Forty-five SD rats were randomly divided into 3 groups: The control group (Con group, n=15), the model group (VD group, n=15) and the resveratrol-treated VD group (Res group, n=15). The VD rats (the VD group and the Res group) were generated by bilateral common carotid artery occlusion. The rats in the Res group received daily resveratrol treatment intraperitoneally for 4 weeks. Cognitive function was tested using the Morris water maze test. The levels of SOD and MDA (oxidative stress indicators) were detected by ELISA kits. The protein expression of Bax, Bcl-2 and caspase-3 was detected by western blotting. Compared with the rats in the Con group, the rats in the VD group exhibited decreased cognitive function, significantly increased hippocampal content of MDA, Bax and caspase-3 (P<0.05), and significantly reduced hippocampal expression of SOD and Bcl-2 (P<0.05). Compared with the rats in the VD group, the rats in the Res group exhibited increased cognitive ability, reduced hippocampal content of MDA, Bax and caspase-3 (P<0.05), and increased hippocampal expression of SOD and Bcl-2 (P<0.05). Resveratrol treatment significantly improved the spatial learning and memory of the VD rats. The mechanism associated with the neuroprotective effects of resveratrol may be closely related to the inhibition of the apoptosis pathway and oxidative stress injury.

Integration of transcriptomics and metabolomics data can provide detailed information for better understanding the molecular mechanisms underlying salt tolerance in rice. In the present study, we report a comprehensive analysis of the transcriptome and metabolome of rice overexpressing the OsDRAP1 gene, which encodes an ERF transcription factor and was previously identified to be conferring drought tolerance. Phenotypic analysis showed that OsDRAP1 overexpression (OE) improved salt tolerance by increasing the survival rate under salt stress. OsDRAP1 affected the physiological indices such as superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) to enhance redox homeostasis and membrane stability in response to salt stress. Higher basal expression of OsDRAP1 resulted in differential expression of genes that potentially function in intrinsic salt tolerance. A core set of genes with distinct functions in transcriptional regulation, organelle gene expression and ion transport were substantially up-regulated in the OE line in response to salt stress, implying their important role in OsDRAP1-mediated salt tolerance. Correspondingly, metabolome profiling detected a number of differentially metabolites in the OE line relative to the wild type under salt stress. These metabolites, including amino acids (proline, valine), organic acids (glyceric acid, phosphoenolpyruvic acid and ascorbic acid) and many secondary metabolites, accumulated to higher levels in the OE line, demonstrating their role in salt tolerance. Integration of transcriptome and metabolome analysis highlights the crucial role of amino acids and carbohydrate metabolism pathways in OsDRAP1-mediated salt tolerance.

Rice (Oryza sativa) is very sensitive to chilling stress at seedling and reproductive stages, whereas wild rice, O. longistaminata, tolerates non-freezing cold temperatures and has overwintering ability. Elucidating the molecular mechanisms of chilling tolerance (CT) in O. longistaminata should thus provide a basis for rice CT improvement through molecular breeding. In this study, high-throughput RNA sequencing was performed to profile global transcriptome alterations and crucial genes involved in response to long-term low temperature in O. longistaminata shoots and rhizomes subjected to 7 days of chilling stress. A total of 605 and 403 genes were respectively identified as up- and down-regulated in O. longistaminata under 7 days of chilling stress, with 354 and 371 differentially expressed genes (DEGs) found exclusively in shoots and rhizomes, respectively. GO enrichment and KEGG pathway analyses revealed that multiple transcriptional regulatory pathways were enriched in commonly induced genes in both tissues; in contrast, only the photosynthesis pathway was prevalent in genes uniquely induced in shoots, whereas several key metabolic pathways and the programmed cell death process were enriched in genes induced only in rhizomes. Further analysis of these tissue-specific DEGs showed that the CBF/DREB1 regulon and other transcription factors (TFs), including AP2/EREBPs, MYBs, and WRKYs, were synergistically involved in transcriptional regulation of chilling stress response in shoots. Different sets of TFs, such as OsERF922, OsNAC9, OsWRKY25, and WRKY74, and eight genes encoding antioxidant enzymes were exclusively activated in rhizomes under long-term low-temperature treatment. Furthermore, several cis-regulatory elements, including the ICE1-binding site, the GATA element for phytochrome regulation, and the W-box for WRKY binding, were highly abundant in both tissues, confirming the involvement of multiple regulatory genes and complex networks in the transcriptional regulation of CT in O. longistaminata. Finally, most chilling-induced genes with alternative splicing exclusive to shoots were associated with photosynthesis and regulation of gene expression, while those enriched in rhizomes were primarily related to stress signal transduction; this indicates that tissue-specific transcriptional and post-transcriptional regulation mechanisms synergistically contribute to O. longistaminata long-term CT. Our findings provide an overview of the complex regulatory networks of CT in O. longistaminata.

Background: High soil salinity can cause significant losses in rice productivity worldwide, mainly because salt inhibits plant growth and reduces grain yield. To cope with environmental changes, plants have evolved several adaptive mechanisms that involve the regulation of many stress-responsive genes. Results: In this study, we identified OsSTAP1, which encodes an AP2/ERF-type transcription factor, was rapidly induced by ABA, ACC, salt, cold, and PEG treatments. OsSTAP1 is localized to the nucleus and acts as a transcriptional activator in plant cells. Compared with wild type, transgenic lines overexpressing OsSTAP1 exhibited increased tolerance to salt stress with higher SOD, POD, and CAT activities, and lower Na + /K + ratios in the shoots. In addition, many other stress-responsive genes, including other ERF-and peroxidase-encoding genes, were upregulated in the OsSTAP1-overexpression lines. Conclusion: This study suggests that OsSTAP1 functions as an AP2/ERF transcriptional activator, and plays a positive role in salt tolerance by decreasing the Na + /K + ratio and maintaining cellular redox homeostasis.

N6-methyladenosine (m6A) methylation represents a new layer of the epitranscriptomic regulation of plant development and growth. However, the effects of m6A on rice responses to environmental stimuli remain unclear. In this study, we performed a methylated-RNA immunoprecipitation sequencing analysis and compared the changes in m6A methylation and gene expression in rice under salt stress conditions. Salt stress significantly increased the m6A methylation in the shoots (p value < 0.05). Additionally, 2537 and 2304 differential m6A sites within 2134 and 1997 genes were identified in the shoots and roots, respectively, under salt stress and control conditions. These differential m6A sites were largely regulated in a tissue-specific manner. A unique set of genes encoding transcription factors, antioxidants, and auxin-responsive proteins had increased or decreased m6A methylation levels only in the shoots or roots under salt stress, implying m6A may mediate salt tolerance by regulating transcription, ROS homeostasis, and auxin signaling in a tissue-specific manner. Integrating analyses of m6A modifications and gene expression changes revealed that m6A changes regulate the expression of genes controlling plant growth, stress responses, and ion transport under saline conditions. These findings may help clarify the regulatory effects of m6A modifications on rice salt tolerance.

Gibberellin 2-oxidase (GA2ox) plays an important role in the GA catabolic pathway and the molecular function of the OsGA2ox genes in plant abiotic stress tolerance remains largely unknown. In this study, we functionally characterized the rice gibberellin 2-oxidase 8 (OsGA2ox8) gene. The OsGA2ox8 protein was localized in the nucleus, cell membrane, and cytoplasm, and was induced in response to various abiotic stresses and phytohormones. The overexpression of OsGA2ox8 significantly enhanced the osmotic stress tolerance of transgenic rice plants by increasing the number of osmotic regulators and antioxidants. OsGA2ox8 was differentially expressed in the shoots and roots to cope with osmotic stress. The plants overexpressing OsGA2ox8 showed reduced lengths of shoots and roots at the seedling stage, but no difference in plant height at the heading stage was observed, which may be due to the interaction of OsGA2ox8 and OsGA20ox1, implying a complex feedback regulation between GA biosynthesis and metabolism in rice. Importantly, OsGA2ox8 was able to indirectly regulate several genes associated with the anthocyanin and flavonoid biosynthetic pathway and the jasmonic acid (JA) and abscisic acid (ABA) biosynthetic pathway, and overexpression of OsGA2ox8 activated JA signal transduction by inhibiting the expression of jasmonate ZIM domain-containing proteins. These results provide a basis for a future understanding of the networks and respective phenotypic effects associated with OsGA2ox8.