OsbZIP23 is a member of the basic leucine zipper (bZIP) transcription factor family in rice (Oryza sativa). Expression of OsbZIP23 is strongly induced by a wide spectrum of stresses, including drought, salt, abscisic acid (ABA), and polyethylene glycol treatments, while other stress-responsive genes of this family are slightly induced only by one or two of the stresses. Transactivation assay in yeast demonstrated that OsbZIP23 functions as a transcriptional activator, and the sequences at the N terminus (amino acids 1-59) and a region close to the C terminus (amino acids 210-240) are required for the transactivation activity. Transient expression of OsbZIP23-green fluorescent protein in onion (Allium cepa) cells revealed a nuclear localization of the protein. Transgenic rice overexpressing OsbZIP23 showed significantly improved tolerance to drought and high-salinity stresses and sensitivity to ABA. On the other hand, a null mutant of this gene showed significantly decreased sensitivity to a high concentration of ABA and decreased tolerance to high-salinity and drought stress, and this phenotype can be complemented by transforming the OsbZIP23 back into the mutant. GeneChip and real-time polymerase chain reaction analyses revealed that hundreds of genes were up-or down-regulated in the rice plants overexpressing OsbZIP23. More than half of these genes have been annotated or evidenced for their diverse functions in stress response or tolerance. In addition, more than 30 genes that are possible OsbZIP23-specific target genes were identified based on the comparison of the expression profiles in the overexpressor and the mutant of OsbZIP23. Collectively, these results indicate that OsbZIP23 functions as a transcriptional regulator that can regulate the expression of a wide spectrum of stress-related genes in response to abiotic stresses through an ABA-dependent regulation pathway. We propose that OsbZIP23 is a major player of the bZIP family in rice for conferring ABA-dependent drought and salinity tolerance and has high potential usefulness in genetic improvement of stress tolerance.

The TIFY family is a novel plant-specific gene family involved in the regulation of diverse plant-specific biologic processes, such as development and responses to phytohormones, in Arabidopsis. However, there is limited information about this family in monocot species. This report identifies 20 TIFY genes in rice, the model monocot species. Sequence analysis indicated that rice TIFY proteins have conserved motifs beyond the TIFY domain as was previously shown in Arabidopsis. On the basis of their protein structures, members of the TIFY family can be divided into two groups. Transcript level analysis of OsTIFY genes in tissues and organs revealed different tempo-spatial expression patterns, suggesting that expression and function vary by stage of plant growth and development. Most of the OsTIFY genes were predominantly expressed in leaf. Nine OsTIFY genes were responsive to jasmonic acid and wounding treatments. Interestingly, almost all the OsTIFY genes were responsive to one or more abiotic stresses including drought, salinity, and low temperature. Over-expression of OsTIFY11a, one of the stress-inducible genes, resulted in significantly increased tolerance to salt and dehydration stresses. These results suggest that the OsTIFY family may have important roles in response to abiotic stresses. The data presented in this report provide important clues for further elucidating the functions of the genes in the OsTIFY family.

The outermost surfaces of plants are covered with an epicuticular wax layer that provides a primary waterproof barrier and protection against different environmental stresses. Glossy 1 (GL1) is one of the reported genes controlling wax synthesis. This study analyzed GL1-homologous genes in Oryza sativa and characterized the key members of this family involved in wax synthesis and stress resistance. Sequence analysis revealed 11 homologous genes of GL1 in rice, designated OsGL1-1 to OsGL1-11. OsGL1-1, -2 and -3 are closely related to GL1. OsGL1-4, -5, -6, and -7 are closely related to Arabidopsis CER1 that is involved in cuticular wax biosynthesis. OsGL1-8, -9, -10 and -11 are closely related to SUR2 encoding a putative sterol desaturase also involved in epicuticular wax biosynthesis. These genes showed variable expression levels in different tissues and organs of rice, and most of them were induced by abiotic stresses. Compared to the wild type, the OsGL1-2-over-expression rice exhibited more wax crystallization and a thicker epicuticular layer; while the mutant of this gene showed less wax crystallization and a thinner cuticular layer. Chlorophyll leaching experiment suggested that the cuticular permeability was decreased and increased in the over-expression lines and the mutant, respectively. Quantification analysis of wax composition by GC-MS revealed a significant reduction of total cuticular wax in the mutant and increase of total cuticular wax in the over-expression plants. Compared to the over-expression and wild type plants, the osgl1-2 mutant was more sensitive to drought stress at reproductive stage, suggesting an important role of this gene in drought resistance.

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In order to understand cold adaptability and explore additional genetic resources for the cold tolerance improvement of rice, we investigated the genetic variation of 529 rice accessions under natural chilling and cold shock stress conditions at the seedling stage using genome-wide association studies; a total of 132 loci were identified. Among them, 12 loci were common for both chilling and cold shock tolerance, suggesting that rice has a distinct and overlapping genetic response and adaptation to the two stresses. Haplotype analysis of a known gene OsMYB2, which is involved in cold tolerance, revealed indica-japonica differentiation and latitude tendency for the haplotypes of this gene. By checking the subpopulation and geographical distribution of accessions with tolerance or sensitivity under these two stress conditions, we found that the chilling tolerance group, which mainly consisted of japonica accessions, has a wider latitudinal distribution than the chilling sensitivity group. We conclude that the genetic basis of natural chilling stress tolerance in rice is distinct from that of cold shock stress frequently used for low-temperature treatment in the laboratory and the cold adaptability of rice is associated with the subpopulation and latitudinal distribution.

Cold stress is one of the major constraints for crop yield. Plants have in turn evolved highly sophisticated mechanisms involving altered physiologic and biochemical processes to cope with the cold stress. Previous studies have revealed that the INDUCER OF CBF EXPRESSION 1 (ICE1), a basic helix-loop-helix (bHLH) transcription factor, directly binds and activates the expression of C-Repeat Binding Factor/ Dehydration-Responsive-Element-Binding protein (CBF/DREB1) to regulate the cold-response pathway in Arabidopsis thaliana. However, the function of AtICE1 orthologues in rice is largely unknown. Here we identified that OsICE1 and OsICE2 in rice shared highly conserved amino acid sequence with AtICE1 in Arabidopsis. Overexpression of OsICE1 and OsICE2 in Arabidopsis significantly enhanced the cold tolerance of Arabidopsis seedlings and improved the expression of cold-response genes. Furthermore, we showed that both OsICE1 and OsICE2 physically interact with OsMYBS3, a single DNA-binding repeat MYB transcription factor that is essential for cold adaptation in rice, suggesting that OsICE1/OsICE2 and OsMYBS3 probably act through specific signal transduction mechanisms to coordinate cold tolerance in rice. These results demonstrated that the 2 OsICEs are orthologues of AtICE1 and play positive regulators in activation of cold-response genes to regulate the cold tolerance.

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis in China. Recently, a shift in molecular epidemiology from hepatitis E genotype 1 (HEV-1) to hepatitis E genotype 4 (HEV-4) has been observed in Northern China, marking a switch from human-to-human transmission to zoonosis. However, similar data from cities in Southern China are lacking. This observational study of human hepatitis E cases in Shenzhen, a metropolitan city in the Pearl River Delta region, aimed to describe the clinical features and molecular epidemiology of hepatitis E in Southern China. Over a 55-month period, we identified 20 patients with acute hepatitis E. Most were middle-aged men, and 50% of patients had concomitant liver disease, of whom 70% were identified to have non-alcoholic fatty liver disease; such patients had a trend toward higher liver enzymes. Quantitative real-time RT-PCR using archived serum samples showed that 12 patients had hepatitis E viremia at presentation. Sequencing of the RNA-dependent RNA polymerase gene was performed for five of these patients, and phylogenetic analysis revealed that these five HEV isolates belonged to subgenotype 4b and were clustered with swine HEV isolates from Southern China. Combined with other studies showing similar findings, this suggests that the molecular epidemiology of hepatitis E in China is evolving toward low-level endemicity driven by foodborne transmission from seafood or pork products. The importance of concomitant liver disease, in particular non-alcoholic fatty liver disease, as a risk factor for severe hepatitis E requires further study.

Background: 2′, 5′-oligoadenylate synthetase 2 (OAS2) has been known as an antiviral interferon-stimulated gene (ISG). However, the role of OAS2 on Zika virus (ZIKV) replication is still unknown. In this study, we sought to explore the effect of OAS2 on ZIKV replication and its underlying mechanism. Methods: We performed RNA-Seq in A549 cells with or without ZIKV infection. OAS2 or RIG-I was overexpressed by plasmid transfection or knocked down by siRNA in A549 cells. Expression levels of mRNA and protein of selected genes were detected by RT-qPCR and Western Blot, respectively. Interferon stimulated response element (ISRE) activity was examined by dual luciferase assay. Results: We found that ZIKV infection induced OAS2 expression through a RIG-I-dependent pathway. OAS2 overexpression inhibited ZIKV replication, while OAS2 knockdown increased ZIKV replication. We observed that OAS2 inhibited ZIKV replication through enhanced IFNβ expression, leading to the activation of the Jak/STAT signaling pathway. Conclusion: ZIKV infection induced OAS2 expression, which in turn exerted its anti-ZIKV activities through the IFN-activated Jak/STAT signaling pathway.