Virus-induced gene complementation reveals a transcription factor network in modulation of tomato fruit ripening

Plant virus technology, in particular virus-induced gene silencing, is a widely used reverse- and forward-genetics tool in plant functional genomics. However the potential of virus technology to express genes to induce phenotypes or to complement mutants in order to understand the function of plant genes is not well documented. Here we exploit Potato virus X as a tool for virus-induced gene complementation (VIGC). Using VIGC in tomato, we demonstrated that ectopic viral expression of LeMADS-RIN, which encodes a MADS-box transcription factor (TF), resulted in functional complementation of the non-ripening rin mutant phenotype and caused fruits to ripen. Comparative gene expression analysis indicated that LeMADS-RIN up-regulated expression of the SBP-box (SQUAMOSA promoter binding protein-like) gene LeSPL-CNR, but down-regulated the expression of LeHB-1, an HD-Zip homeobox TF gene. Our data support the hypothesis that a transcriptional network may exist among key TFs in the modulation of fruit ripening in tomato

RNA silencing suppressors : how viruses fight back

RNA silencing is a collective term that refers to diverse RNA-directed processes resulting in sequence-specific degradation of target RNA and repression of gene expression, either at transcriptional or post-transcriptional levels. In animals, fungi and plants, RNA silencing represents a mechanism guided by small RNAs against virus infection. Viruses can be inducers and targets of RNA silencing, and have evolved active and passive strategies to counter the cellular antiviral mechanism. This review discusses various approaches, including protein- and RNA-mediated silencing suppression and viral escape of RNA silencing without suppression, to highlight how viruses could fight back to survive under the universal host surveillance

Decreased level of ferredoxin I in Tobacco mosaic virus-infected tobacco is associated with development of the mosaic symptom

A decrease of ferredoxin I (Fd I) level was detected in the Tobacco mosaic virus (TMV)-infected tobacco (Nicotiana tabacum) leaves and the extent of decrease was uneven in the leaves showing mosaic symptoms. The Fd I level in the dark-green regions which contain less TMV was higher than that in the chlorotic regions of the same leaf, but was lower than that in the healthy control plants. The N. benthamiana plants with the Fed-1 gene being silenced by a chimeric viral vector showed chlorotic and yellowish phenotype in which H2O2 accumulated to a high level. In antisense Fed-1 transgenic N. benthamiana plants, the multiplication of TMV in infected plants and the accumulation of the viral coat protein in the chloroplasts were enhanced by the decrease of Fd I. Taken together, these results suggest that the unevenly decreased level of Fd I in TMV-infected tobacco leaves may contribute to the expression of chlorosis and mosaic symptoms. (C) 2008 Elsevier Ltd. All rights reserved

More Features in Bound Representations Does Not Require Extra Object-based Attention in Working Memory

PURPOSE: Feature binding is a core concept in many research fields, including the study of working memory (WM).We recently proposed that binding in WM is not passive, but requires more object-based attention to actively bind distinct single features into a coherent unit (Gao et al., Attention, Perception, &amp; Psychophysics, 2017; Shen, Huang, &amp; Gao, Journal of Experimental Psychology: Human Perception and Performance, 2015). However, a hallmark of object-based attention&mdash;the amount of attention is not modulated by the number features contained in an object&mdash;has not been examined. In the current study, we closed this gap by examining whether this hallmark of object-based attention still holds in WM. METHODS: In two experiments, we required the participants to memorize three bound representations, and manipulated the number of features (2 vs. 3 features) contained in each binding. To examine the role of object-based attention in retaining bindings in WM, we also manipulated whether a secondary task consuming object-based attention was interpolated into the maintenance phase of WM (with vs. without secondary task). If more object-based attention was required after an extra feature was added into the bound representation, then the secondary task would result in worse performance for 3-featured binding than 2-featured binding. RESULTS: In two experiments, we consistently found that the added secondary task significantly impaired the binding performance. However, the added secondary task impaired the 2-featured and 3-featured bindings to the same extent. CONCLUSION: The number of features contained in binding does not modulate the required object-based attention for binding in WM, suggesting that WM and perception share the same hallmark of object-based attention.</p

Retaining Bindings of Integral Features in Working Memory: The Role of Object-based Attention

PURPOSE: Over the past decade, it has been debated whether retaining bindings in working memory (WM) requires more attention than retaining constituent features, focusing on domain-general attention and space-based attention. Recently we proposed that retaining bindings in WM needs more object-based attention than retaining constituent features (Gao et al., 2017; Shen, Huang, &amp; Gao, 2015). However, the composed features in the tested bindings all belong to separable feature dimensions. It has been suggested that there are two types of feature relations: Separable features (e.g., color and shape in a colored shape) and integral features (e.g., width and height of a rectangle). While our brain encodes separable features independently, it is difficult to encode the integral features separately. Consequently, the object-based attention hypothesis of retaining bindings in WM may be constrained to separable features, and retaining bindings of integral features does not require more object-based attention than the constitute single features. METHODS: In the current study we addressed this issue by requiring the participants to memorize both width and height of three rectangles or the binding between the two feature dimensions. In the critical condition, we added a secondary transparent motion task during the delay interval of the change-detection task, such that the secondary task competed for object-based attention with the to-be-memorized stimuli. If more object-based attention is required for retaining bindings than for retaining constituent features, the secondary task should impair the binding performance to a larger degree relative to the performance of constituent features. RESULTS: In contrast to the prediction of object-based attention hypothesis, the added secondary task equally impaired the performance of single features and binding. CONCLUSION: Retaining bindings of integral features in WM does not require more object-based attention than the constitute single features, providing a key constraint to the object-based attention hypothesis.</p

Comparison of nanoindentation measurements between osteogenesis imferfecta type III and type IV and between different anatomic locations (Femur/Tibia versus iliac crest

Nanoindentation was used to compare the intrinsic mechanical properties of bone tissue (iliac crest biopsy) from children with type III and type IV osteogenesis imperfecta (OI). Young&apos;s modulus and hardness values were not significantly different between the two clinical severity groups on either cortical or trabecular measurement. In comparing the ratio of modulus over hardness (E/H) between OI type III and IV. The type III bone showed a marginally significant decrease for cortical bone and significant decrease for trabecular bone, which indicated that the OI type III bone was more brittle than OI type IV bone at the tissue level. In addition, nanoindentation measurements of the bone tissue harvested at femur/tibia from the same patients were compared with the results from the iliac crest biopsy. Young&apos;s modulus and hardness values were not significantly different between the two anatomic locations in either cortical or trabecular measurements. The ratio of E/H was not significantly different between the two groups. Results indicate that intrinsic modulus, hardness, and indentation deformation pattern (E/H) of OI bone tissues are not significantly different at long bone (midshaft of femur/tibia) and iliac crest. We observed that age (1.9 to 13.2 years) did not influence OI bone tissue intrinsic mechanical properties

Virus-Derived Small Interfering RNAs Affect the Accumulations of Viral and Host Transcripts in Maize

RNA silencing is a conserved surveillance mechanism against invading viruses in plants, which involves the production of virus-derived small interfering RNAs (vsiRNAs) that play essential roles in the silencing of viral RNAs and/or specific host transcripts. However, how vsiRNAs function to target viral and/or host transcripts is poorly studied, especially in maize (Zea mays L.). In this study, a degradome library constructed from Sugarcane mosaic virus (SCMV)-inoculated maize plants was analyzed to identify the cleavage sites in viral and host transcripts mainly produced by vsiRNAs. The results showed that 42 maize transcripts were possibly cleaved by vsiRNAs, among which several were involved in chloroplast functions and in biotic and abiotic stresses. In addition, more than 3000 cleavage sites possibly produced by vsiRNAs were identified in positive-strand RNAs of SCMV, while there were only four cleavage sites in the negative-strand RNAs. To determine the roles of vsiRNAs in targeting viral RNAs, six vsiRNAs were expressed in maize protoplast based on artificial microRNAs (amiRNAs), of which four could efficiently inhibit the accumulations of SCMV RNAs. These results provide new insights into the genetic manipulation of maize with resistance against virus infection by using amiRNA as a more predictable and useful approach

Quasi-static and dynamic nanoindentation studies on highly crosslinked ultra-high-molecular-weight polyethylene

In four separate studies, the effect of three methods used to highly crosslink ultra-high-molecular-weight polyethylene (UHMWPE) (gamma irradiation, electron beam irradiation, and peroxide treatment) on the polymer\u27s stiffness was investigated using quasi-static and dynamic nanoindentation. From the quasi-static studies, it was found that (a) the highest value of the elastic modulus, E (2240±157MPa) was obtained from specimens prepared from direct compression molded UHMWPE crosslinked using gamma irradiation, with a dosage of 7.5Mrad; (b) the value of E for specimens formed from direct compression molded UHMWPE was higher (1950±255MPa) compared to results obtained from specimens formed from ram extruded UHMWPE (1583±140MPa); and (c) the magnitude of the decrease in the value of E as a result of subjecting a highly crosslinked UHMWPE specimen to uniaxial tensile forces depends on the method used for the crosslinking. From the dynamic study, (d) it was found that the extent of the change in both the storage modulus and the loss modulus, as a result of subjecting a highly crosslinked UHMWPE specimen to uniaxial tension forces, depends on the method used for the crosslinking. © 2003 Elsevier Ltd. All rights reserved

Influence of an m-type thioredoxin in maize on potyviral infection

Expression of many host genes can be altered during virus infection. In a previous study of sugarcane mosaic virus (SCMV) infection in maize (Zea mays), we observed that expression of ZmTrm2, a gene encoding thioredoxin m, was up-regulated at about 10 days post-inoculation (dpi). In this present study we determined that ZmTrm2 silencing in maize by virus-induced gene silencing significantly enhanced systemic SCMV infection. In contrast transient over-expression of ZmTrm2 in maize protoplasts inhibited accumulation of SCMV viral RNA. Furthermore, we found that in inoculated Nicotiana tabacum leaves transient expression of ZmTrm2 inhibited accumulation of the RNA of tobacco vein-banding mosaic virus (TVBMV), a potyvirus infecting dicotyledonous plants. Interestingly in ZmTrm2 transiently expressed N. tabacum leaves, we detected by semi-quantitative RT-PCR a reduced level of the mRNA of class I beta-1, 3-glucanase (GluI), a protein known to have a role in cell wall callose deposition and viral movement. Our data indicate that the maize ZmTrm2 plays an inhibitory role during infection of plants by SCMV and TVBMV