First Report of Dieback Caused by Lasiodiplodia pseudotheobromae on Ormosia pinnata in China.

Ormosia pinnata (Lour.) Merr. is an important tree used for landscape and plant recovery of barren slopes in China. During an investigation of plant disease on landscape trees in 2018, a dieback was observed on O. pinnata trees in Guangzhou, Guangdong Province, China. Symptoms were characterized by initial dryness of the twigs and eventual death of the whole branch of the tree. Isolations from symptomatic branches yielded 13 isolates including two main morphotypes. Pathogenicity tests showed that isolate GDOP1 from Type I caused dieback of O. pinnata. Based on morphological characteristics and molecular analysis of the internal transcribed spacer rDNA (ITS1-5.8S-ITS2) and partial sequence of the translation elongation factor 1α (EF1-α), the fungus causing dieback on O. pinnata was identified as Lasiodiplodia pseudotheobromae. This is the first report of L. pseudotheobromae infecting O. pinnata in the world.

Spatial and temporal expression modes of MicroRNAs in an elite rice hybrid and its parental lines.

Heterosis is a commonly observed phenomenon in nature and refers to the superior performance of hybrids relative to both parents. The molecular mechanisms of heterosis are mostly unknown. Quantitative trait locus (QTL) mapping has been used to explain the genetic basis of heterosis, and large amounts of QTLs have been mapped for various agronomic traits, but the nature of QTL contributing to heterosis is still enigmatic. MicroRNAs (miRNAs) are master regulators in the processes of plant development and trait performance, and many miRNAs are predicted to reside in QTL intervals. We analyzed the expression modes of miRNAs, which were picked up from miRNA databases and chosen from those predicted from QTL intervals by bioinformatic approaches, in different organs at developmental stages of an elite rice hybrid and its parents. All possible modes of action for miRNA expression were detected, but most miRNAs showed nonadditive mode, and different stages and distinct organs displayed different patterns of miRNA expression. A large proportion of miRNAs were not detected for expression in leaves but expressed in the culms and roots of the hybrid at tillering stage. MiRNAs from grain-weight QTL intervals have multiple effects on grain development. Together, our results reveal that miRNAs, especially those from QTL intervals, play roles in heterotic performance in this elite rice hybrid, our results also shade new light on understanding the molecular mechanisms of heterosis.

Comparative Study of the Co-Occurring Alternaria and Colletotrichum Species in the Production of Citrus Leaf Spot.

Both of the two citrus diseases, Alternaria brown spot (ABS) and Anthracnose, caused by Alternaria and Colletotrichum spp., respectively, can produce leaf lesions which are hard to differentiate. These two diseases have been confused as causal agents of brown spot for over a decade in China. In this study, citrus leaves with or without brown spot were collected from Zhaoqing, Guangdong and Wanzhou, Chongqing, and were further used for the taxonomic and functional comparisons between the co-occurring Alternaria and Colletotrichum species. In the amplicon sequencing, the average relative abundance and the composition of Alternaria, but not Colletotrichum, increased (from 0.1 to 9.9, p = 0.059; and to 0.7, p < 0.05) and significantly altered (p < 0.01) with the brown spot in Zhaoqing and Wanzhou, respectively. Two representative isolates Alternaria sp. F12A and Colletotrichum sp. F12C, from the same brown spot, were proved with different virulence and host response activation to citrus leaves. F12A caused typical symptoms of brown spot with the average spot length expanded to 5 and 6.1 cm, and also altered the citrus global gene expression 48 and 72 h after inoculation. In addition, F12A enriched the expression of genes that were most frequently involved in plant defense. In comparison, F12C caused leaf spot limited to the wounded site, and its milder activation of host response recovered 72 h after inoculation. Our study indicates that the incidence of brown spot in China is caused by Alternaria species, and the ABS should be a fungal disease of major concern on citrus.

A novel rice calmodulin-like gene, OsMSR2, enhances drought and salt tolerance and increases ABA sensitivity in Arabidopsis.

Many abiotic stimuli, such as drought and salt stresses, elicit changes in intracellular calcium levels that serve to convey information and activate adaptive responses. Ca²âº signals are perceived by different Ca²âº sensors, and calmodulin (CaM) is one of the best-characterized Ca²âº sensors in eukaryotes. Calmodulin-like (CML) proteins also exist in plants, but their functions at the physiological and molecular levels are largely unknown. In this report, we present data on OsMSR2 (Oryza sativa L. Multi-Stress-Responsive gene 2), a novel calmodulin-like protein gene isolated from rice Pei'ai 64S (Oryza sativa L.). Expression of OsMSR2 was strongly up-regulated by a wide spectrum of stresses, including cold, drought, and heat in different tissues at different developmental stages of rice, as revealed by both microarray and quantitative real-time RT-PCR analyses. Analysis of the recombinant OsMSR2 protein demonstrated its potential ability to bind Ca²âº in vitro. Expression of OsMSR2 conferred enhanced tolerance to high salt and drought in Arabidopsis (Arabidopsis thaliana) accompanied by altered expression of stress/ABA-responsive genes. Transgenic plants also exhibited hypersensitivity to ABA during the seed germination and post-germination stages. The results suggest that expression of OsMSR2 modulated salt and drought tolerance in Arabidopsis through ABA-mediated pathways.

MiR-339 attenuates LPS-induced intestinal epithelial cells inflammatory responses and apoptosis by targeting TLR4.

BACKGROUND: Intestinal epithelial cells are important for defending against pathogen infection. LPS is an endotoxin that is highly antigenic and cytotoxic produced by bacteria. LPS disrupts the intestine epithelium integrity and induced the intestinal epithelial cell inflammation and apoptosis. Our previous study has predicted the function of exosome miRNAs through bioinformatics analysis, and we found that miR-339 had a potential function in cell inflammation response. To our knowledge, no published paper has demonstrated the miR-339 function in protecting the intestine epithelium against bacterial infection. OBJECTIVE: The objective of this study is to evaluate the miR-339 function in regulating intestinal epithelial cells to defend against bacterial infection through biological experiments and bioinformatics analyses. METHODS: Through the miR-339 transfection experiment and TLR4 interfering experiment, we evaluated the function of miR-339 and TLR4 in the process of inflammatory responses and apoptosis. Through Bioinformatics analyses and dual-luciferase reporter experiment, we identified the target gene of miR-339. RESULTS: miR-339 attenuates LPS-induced intestinal epithelial cells inflammatory responses through the TLR4/NF-κB signaling pathway and inhibited LPS-induced apoptosis through the P53 signaling pathway. TLR4 is the target gene of miR-339. TLR4 reduced LPS-induced proinflammatory responses and apoptosis. CONCLUSIONS: In conclusion, miR-339 protected the intestine epithelial cells from LPS-induced cell inflammation and apoptosis through targeting TLR4. This study expanded our understanding of how miRNAs and genes work collaboratively in regulating intestinal epithelial cells to defend against bacterial infection.