In addition to regulating growth and development, the most important function of microRNAs (miRNAs) in plants is the regulation of a variety of cellular processes underlying plant adaptation to environmental stresses. To gain a deep understanding of the mechanism of drought tolerance in rice, genome-wide profiling and analysis of miRNAs was carried out in drought-challenged rice across a wide range of developmental stages, from tillering to inflorescence formation, using a microarray platform. Among the 30 miRNAs identified as significantly down- or up-regulated under the drought stress, 11 down-regulated miRNAs (miR170, miR172, miR397, miR408, miR529, miR896, miR1030, miR1035, miR1050, miR1088, and miR1126) and eight up-regulated miRNAs (miR395, miR474, miR845, miR851, miR854, miR901, miR903, and miR1125) were revealed for the first time to be induced by drought stress in plants, and nine (miR156, miR168, miR170, miR171, miR172, miR319, miR396, miR397, and miR408) showed opposite expression to that observed in drought-stressed Arabidopsis. The most conserved down-regulated miRNAs were ath-miR170, the miR171 family, and ath-miR396, and the most conserved up-regulated miRNAs were ptc-miR474 and ath-miR854a. The identification of differentially expressed novel plant miRNAs and their target genes, and the analysis of cis-elements provides molecular evidence for the possible involvement of miRNAs in the process of drought response and/or tolerance in rice.

Salinity is one of the most important abiotic stress affecting the world rice production. The cultivation of salinity-tolerant cultivars is the most costeffective and environmentally friendly approach for salinity control. In recent years, CRISPR/Cas9 systems have been widely used for target-site genome editing; however, their application for the improvement of elite rice cultivars has rarely been reported. Here, we report the improvement of the rice salinity tolerance by engineering a Cas9-OsRR22-gRNA expressing vector, targeting the OsRR22 gene in rice. Nine mutant plants were identified from 14 T 0 transgenic plants. Sequencing showed that these plants had six mutation types at the target site, all of which were successfully transmitted to the next generations. Mutant plants without transferred DNA (T-DNA) were obtained via segregation in the T1 generations. Two T2 homozygous mutant lines were further examined for their salinity tolerance and agronomic traits. The results showed that, at the seedling stage, the salinity tolerance of T2 homozygous mutant lines was significantly enhanced compared to wild-type plants. Furthermore, no significantly different agronomic traits were found between T2 homozygous mutant lines and wild-type plants. Our results indicate CRISPR/ Cas9 as a useful approach to enhance the salinity tolerance of rice.

A novel gene, OsAHL1, containing an AT-hook motif and a PPC domain was identified through genome-wide profiling and analysis of mRNAs by comparing the microarray of drought-challenged versus normally watered rice. The results indicated OsAHL1 has both drought avoidance and drought tolerance that could greatly improve drought resistance of the rice plant. Overexpression of OsAHL1 enhanced multiple stress tolerances in rice plants during both seedling and panicle development stages. Functional studies revealed that OsAHL1 regulates root development under drought condition to enhance drought avoidance, participates in oxidative stress response and also regulates the content of chlorophyll in rice leaves. OsAHL1 specifically binds to the A/T rich sequence region of promoters or introns, and hence directly regulates the expression of many stress related downstream genes.

Our work aims to elucidate the effect how microRNA‐148b (miR‐148b) participated in myocardial ischemia/reperfusion (I/R) injury via regulation of Wnt/β‐catenin signaling pathway. The in vivo myocardial I/R models of SD rats and in vitro hypoxia/reoxygenation (H/R) models of H9C2 cells were established. The heart function and infarction area of rats and lactic dehydrogenase (LDH), creatine kinase (CK), malondialdehyde (MDA), and superoxide dismutase (SOD) levels were evaluated. Myocardial cell viability was measured using positron emission tomography combined with computer tomography and (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, and the apoptosis was assessed by terminal deoxynucleotidyl transferase‐mediated nick‐end labeling method and flow cytometry; quantitative reverse‐transcription polymerase chain reaction and western blot were used to detect the related molecules expressions. The myocardial infarction area of rats was significantly increased with reductions in LVSP, + dp/dtmax, − dp/dtmax, LVFS%, LVEF% and standardized uptake value and elevation in left ventricular developed pressure after ischemia/reperfusion (I/R), and the LDH, CK, and MDA levels were enhanced with the decreased SOD. The apoptotic rates were higher in I/R rats and H/R H9C2 cells with upregulated miR‐148b and cleaved caspase‐3, but decreased Bcl‐2/Bax ratio; and meanwhile, the Wnt/β‐catenin pathway was inhibited. Additionally, the H/R‐induced H9C2 cells also exhibited decreased cell viability. MiR‐148b overexpression further aggravated I/R injury of rats, whereas inhibition of miR‐148b reduced I/R and H/R injury through activation of Wnt/β‐catenin pathway. In addition, Wnt‐1 small interfering RNA exposure abolished the effect of miR‐148b inhibitor on H/R injury of H9C2 cells. Inhibition of miR‐148b improved the antioxidative ability and myocardial cell survival to suppress its apoptosis by activating Wnt/β‐catenin signaling pathway, thus ameliorating the myocardial I/R injury.

Background Stigma exsertion rate (SER) is a key determinant of outcrossing in hybrid rice seed production. A quantitative trait locus (QTL) for stigma exsertion rate in rice, qSER-7 , has previously been detected on chromosome 7 by using a F 2 population derived from two indica cytoplasmic male sterility (CMS) maintainers, Huhan 1B and II-32B. Results The chromosomal location of qSER-7 was precisely delimited by fine-scale mapping. Near-isogenic lines (NILs) were established, one of which isolated the locus in the qSER-7 II-32B line, which contains an introgressed segment of II-32B in the Huhan 1B genetic background, and exhibits a significantly higher stigma exsertion rate than that of the recurrent parent. Using 3192 individuals from the BC 4 F 2 segregation population, the QTL qSER-7 was narrowed down to a 28.4-kb region between the markers RM3859 and Indel4373 on chromosome 7. According to the rice genome annotation database, three genes were predicted within the target region. Real-time PCR analysis showed significantly higher expression levels of LOC_Os07g15370 and LOC_Os07g15390 in II-32B than in Huhan 1B. LOC_Os07g15370(OsNRAMP5) was a previously reported gene for Mn and Cd transporter. The stigma exertion rates of OsNRAMP5 -overexpressing plants were significantly higher than that of wild type plants, in contrast, a T-DNA insertion mutant osnramp5 showed a lower stigma exertion rate. Conclusions In the present study, the QTL qSER-7 was isolated to a region between the markers RM3859 and Indel4373. Two candidate genes were selected based on the expression difference between the two parents, which can facilitate the further cloning of the gene underlying the quantitative trait associated with qSER-7 as well as the marker-assisted transfer of desirable genes for stigma exsertion rate improvement in rice. Electronic supplementary material The online version of this article (10.1186/s12284-019-0304-z) contains supplementary material, which is available to authorized users.

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A field demonstration trial comparing the growth status, yield ability and water use efficiency of drought-tolerant rice (Oryza sativa L.) varieties and normal paddy rice variety under drip irrigation and paddy irrigation was carried out for two years in Shanghai, China. Under drip irrigation, both inbred and hybrid water-saving and drought resistant rice (WDR) varieties showed better yield capacity than paddy rice varieties tested. WDR varieties under drip irrigation attained more than 95% of the yield level that is achieved in paddy field, while the paddy varieties under the same drip condition reached only about 75%.The methane gas emission was obviously decreased under drip irrigation condition, while the emission of other greenhouse gas like nitrous oxide or carbon dioxide was not observed significant difference between drip and paddy irrigation. It could be concluded that it is practicable to grow water saving and drought resistant rice through drip irrigation. Drip irrigation maintained a competitive grain yield and water productivity, and greatly reduced pollution risk to the environment. Considering the conservative amount of fertilizer application, less than the amount of fertilization in normal paddy field, the yield potential of rice could be improved by increasing the amount of fertilizer as top application in drip irrigation system.

Water is crucial for plant growth and survival. The transcellular water movement is facilitated by aquaporins (AQPs) that rapidly and reversibly modify water permeability. The abundance of AQPs is regulated by its synthesis, redistribution and degradation. However, the molecular mechanism of proteasomal degradation of AQPs remains unclear. Here, we demonstrate that a novel E3 ligase, OsRINGzf1, mediated the degradation of AQPs in rice. OsRINGzf1 is the candidate gene from a drought-related quantitative trait locus (QTL) on the long arm of chromosome 4 in rice (Oryza sativa) and encodes a Really Interesting New Gene (RING) zinc finger protein 1. OsRINGzf1 possesses the E3 ligase activity, ubiquitinates and mediates OsPIP2;1 degradation, thus reducing its protein abundance. The content of OsPIP2;1 protein was decreased in OsRINGzf1 overexpression (OE) plants. The degradation of OsPIP2;1 was inhibited by MG132. The OsRINGzf1 OE plants, with higher leaf-related water content (LRWC) and lower leaf water loss rate (LWLR), exhibited enhanced drought resistance, whereas the RNAi and knockout plants of OsRINGzf1 were more sensitive to drought. Together, our data demonstrate that OsRINGzf1 positively regulates drought resistance through promoting the degradation of OsPIP2;1 to enhance water retention capacity in rice.