The OsbZIP23 transcription factor has been characterized for its essential role in drought resistance in rice (Oryza sativa), but the mechanism is unknown. In this study, we first investigated the transcriptional activation of OsbZIP23. A homolog of SnRK2 protein kinase (SAPK2) was found to interact with and phosphorylate OsbZIP23 for its transcriptional activation. SAPK2 also interacted with OsPP2C49, an ABI1 homolog, which deactivated the SAPK2 to inhibit the transcriptional activation activity of OsbZIP23. Next, we performed genome-wide identification of OsbZIP23 targets by immunoprecipitation sequencing and RNA sequencing analyses in the OsbZIP23-overexpression, osbzip23 mutant, and wild-type rice under normal and drought stress conditions. OsbZIP23 directly regulates a large number of reported genes that function in stress response, hormone signaling, and developmental processes. Among these targets, we found that OsbZIP23 could positively regulate OsPP2C49, and overexpression of OsPP2C49 in rice resulted in significantly decreased sensitivity of the abscisic acid (ABA) response and rapid dehydration. Moreover, OsNCED4 (9-cis-epoxycarotenoid dioxygenase4), a key gene in ABA biosynthesis, was also positively regulated by OsbZIP23. Together, our results suggest that OsbZIP23 acts as a central regulator in ABA signaling and biosynthesis, and drought resistance in rice.

SummaryRecently, CRISPR‐Cas (clustered, regularly interspaced short palindromic repeats–CRISPR‐associated proteins) system has been used to produce plants resistant to DNA virus infections. However, there is no RNA virus control method in plants that uses CRISPR‐Cas system to target the viral genome directly. Here, we reprogrammed the CRISPR‐Cas9 system from Francisella novicida to confer molecular immunity against RNA viruses in Nicotiana benthamiana and Arabidopsis plants. Plants expressing FnCas9 and sgRNA specific for the cucumber mosaic virus (CMV) or tobacco mosaic virus (TMV) exhibited significantly attenuated virus infection symptoms and reduced viral RNA accumulation. Furthermore, in the transgenic virus‐targeting plants, the resistance was inheritable and the progenies showed significantly less virus accumulation. These data reveal that the CRISPR/Cas9 system can be used to produce plant that stable resistant to RNA viruses, thereby broadening the use of such technology for virus control in agricultural field.

Cold stress is one of the major limiting factors for rice (Oryza sativa) productivity. Several MYB transcriptional factors have been reported as important regulators in the cold stress response, but the molecular mechanisms are largely unknown. In this study, we characterized a cold-responsive R2R3-type MYB gene, OsMYB30, for its regulatory function in cold tolerance in rice. Functional analysis revealed that overexpression of OsMYB30 in rice resulted in increased cold sensitivity, while the osmyb30 knockout mutant showed increased cold tolerance. Microarray and quantitative real-time polymerase chain reaction analyses revealed that a few b-amylase (BMY) genes were down-regulated by OsMYB30. The BMY activity and maltose content, which were decreased and increased in the OsMYB30 overexpression and osmyb30 knockout mutant, respectively, were correlated with the expression patterns of the BMY genes. OsMYB30 was shown to bind to the promoters of the BMY genes. These results suggested that OsMYB30 exhibited a regulatory effect on the breakdown of starch through the regulation of the BMY genes. In addition, application of maltose had a protective effect for cell membranes under cold stress conditions. Furthermore, we identified an OsMYB30-interacting protein, OsJAZ9, that had a significant effect in suppressing the transcriptional activation of OsMYB30 and in the repression of BMY genes mediated by OsMYB30. These results together suggested that OsMYB30 might be a novel regulator of cold tolerance through the negative regulation of the BMY genes by interacting with OsJAZ9 to fine-tune the starch breakdown and the content of maltose, which might contribute to the cold tolerance as a compatible solute.

Jasmonates (JAs) and abscisic acid (ABA) are phytohormones known play important roles in plant response and adaptation to various abiotic stresses including salinity, drought, wounding, and cold. JAZ (JASMONATE ZIM-domain) proteins have been reported to play negative roles in JA signaling. However, direct evidence is still lacking that JAZ proteins regulate drought resistance. In this study, OsJAZ1 was investigated for its role in drought resistance in rice. Expression of OsJAZ1 was strongly responsive to JA treatment, and it was slightly responsive to ABA, salicylic acid, and abiotic stresses including drought, salinity, and cold. The OsJAZ1-overexpression rice plants were more sensitive to drought stress treatment than the wild-type (WT) rice Zhonghua 11 (ZH11) at both the seedling and reproductive stages, while the jaz1 T-DNA insertion mutant plants showed increased drought tolerance compared to the WT plants. The OsJAZ1-overexpression plants were hyposensitive to MeJA and ABA, whereas the jaz1 mutant plants were hypersensitive to MeJA and ABA. In addition, there were significant differences in shoot and root length between the OsJAZ1 transgenic and WT plants under the MeJA and ABA treatments. A subcellular localization assay indicated that OsJAZ1 was localized in both the nucleus and cytoplasm. Transcriptome profiling analysis by RNA-seq revealed that the expression levels of many genes in the ABA and JA signaling pathways exhibited significant differences between the OsJAZ1-overexpression plants and WT ZH11 under drought stress treatment. Quantitative real-time PCR confirmed the expression profiles of some of the differentially expressed genes, including OsNCED4, OsLEA3, RAB21, OsbHLH006, OsbHLH148, OsDREB1A, OsDREB1B, SNAC1, and OsCCD1. These results together suggest that OsJAZ1 plays a role in regulating the drought resistance of rice partially via the ABA and JA pathways.

Plants have evolved complicated protective mechanisms to survive adverse conditions. Previously, we reported that the transcription factor OsbZIP46 regulates abscisic acid (ABA) signaling-mediated drought tolerance in rice () by modulating stress-related genes. An intrinsic D domain represses OsbZIP46 activity, but the detailed mechanism for the repression of OsbZIP46 activation remains unknown. Here, we report an OsbZIP46-interacting protein, MODD (Mediator of OsbZIP46 deactivation and degradation), which is homologous to the ABSCISIC ACID-INSENSITIVE5 binding protein AFP. was induced by ABA and drought stress, but the induction was much slower than that of In contrast to OsbZIP46, MODD negatively regulates ABA signaling and drought tolerance, and inhibits the expression of OsbZIP46 target genes. We found that MODD negatively regulates OsbZIP46 activity and stability. MODD represses OsbZIP46 activity via interaction with the OsTPR3-HDA702 corepressor complex and downregulation of the histone acetylation level at OsbZIP46 target genes. MODD promotes OsbZIP46 degradation via interaction with the U-box type ubiquitin E3 ligase OsPUB70. Interestingly, the D domain is required for both deactivation and degradation of OsbZIP46 via its interaction with MODD. These findings show that plants fine-tune their drought responses by elaborate regulatory mechanisms, including the coordination of activity and stability of key transcription factors.

Histone H2B monoubiquitination (H2Bub1) plays important roles in several physiological and developmental processes, but its roles in the regulation of plant stress responses remain elusive. Here, we report that H2Bub1 is crucially involved in abscisic acid (ABA) signaling and drought response in rice. We found that rice HISTONE MONOUBIQUITINATION2 (OsHUB2), an E3 ligase for H2Bub1, interacted with OsbZIP46, a key transcription factor regulating ABA signaling and drought response in rice. Genetic analyses suggest that OsHUB2, upregulated by drought and ABA, positively modulates ABA sensitivity and drought resistance. The H2Bub1 levels were increased in the target genes of OsbZIP46 under the drought stress and ABA treatments, which were positively correlated with their increased expression levels. Interestingly, MODD, a reported suppressor of ABA signaling and drought resistance by mediating OsbZIP46 deactivation and degradation, could reduce the H2Bub1 levels in the target genes of OsbZIP46 by recruiting a putative deubiquitinase OsOTLD1. Suppression of OsOTLD1 in vivo resulted in increased H2Bub1 levels and expression of OsbZIP46 target genes. Collectively, these findings established an elaborate mechanism of histone monoubiquitination in the fine-turning of ABA signaling and drought response by balancing H2Bub1 deposition and removal.

With the perpetuation of soil salinization, it is imperative to improve the salt and alkaline tolerance of crops. Sorghum bicolor, a C4 crop, is often grown in semiarid areas due to its high tolerance of various abiotic stresses. Whether to improve the resistance of the sorghum itself or that of other crops, it is necessary to understand the response of sorghum under saline–alkali stress. An integrative analysis of the metabolome and transcriptome of sorghum under normal conditions and treatments of moderate and severe saline–alkali stress was performed. Among the different accumulated metabolites (DAMs) and differentially expressed genes (DEGs), flavonoid-related DAMs and DEGs were clearly changed. The level of flavonoids was increased under saline–alkali stress, and the change in flavonoids was dynamic as to whether total flavonoids or most flavonoid components accumulated more under moderate saline–alkali stress compared to severe stress. Some flavonoid metabolites were significantly correlated with the expression of flavonoid biosynthesis genes. MYB transcription factors may also contribute to the regulation of flavonoids levels. These findings present the dynamic changes and possible molecular mechanisms of flavonoids under different saline–alkali stresses and provide a foundation for future research and crop improvement.

Glioblastomas are highly malignant gliomas that are extremely invasive with high rates of recurrence and mortality. It has been reported that activating transcription factor 3 (ATF3) is expressed in elevated levels in multiple malignant tumors. The purpose of this study was to investigate the function of ATF3 in the development of glioma and its clinical significance. Immunohistochemical staining, western blot analysis and RT-qPCR revealed that the mRNA and protein levels of ATF3 and matrix metalloproteinase 2 (MMP2) were higher in the glioma than in the normal human brain tissues, and that their levels were proportional to the pathological grades. By contrast, the mRNA and protein levels of mammary serine protease inhibitor (maspin; SERPINB5) were significantly lower in the glioma than in the normal brain tissue, and maspin expression was inversely proportional to the glioma pathological grade. The transfection of U373MG glioblastoma cells with ATF3-siRNA induced a number of changes in cell behavior; the cell proliferative activity was decreased and flow cytometry revealed an increased proportion of cells arrested in the G0/G1 phase of the cell cycle. In addition, TUNEL staining indicated an increased proportion of cells undergoing apoptosis and Transwell assays revealed impaired cell mobility. The sizes of the tumors grown as xenografts in nude mice were also significantly reduced by treatment of host mice with ATF3-siRNA. Taken together, these results suggest that ATF3 promotes the progression of human gliomas.