MiR-223 modulates multidrug resistance via downregulation of ABCB1 in hepatocellular carcinoma cells.

Multidrug resistance (MDR) has become a major impediment to a successful treatment for liver cancer patients, and one of the common reasons for MDR is the activation of ABCB1 gene, leading to the over-expression of P-glycoprotein (P-gp), which conferred cancer cells be resistant to a broad range of anticancer drugs. MicroRNAs (miRNAs) are a class of short, non-coding RNA moleculars that can regulate gene expression at the post-transcriptional level. In the current study, the aim is to explore whether miRNA participates in the regulation of MDR mediated by ABCB1. We found that the expression of ABCB1 was correlated with the doxorubicin IC50 dose in eight hepatocellular carcinoma (HCC) cell lines: Hep3B, HCC3, LM-6, SMMC7721, Huh-7, SK-Hep-1, HepG2 and BEL-7402. Using the bioinformatics, we discovered that there were several miRNAs that can bind to the 3'UTR of ABCB1 gene. Among these candidate miRNAs, miR-223 was chosen for further study. Then, EGFP reporter assay, real-time PCR and Western blot were performed to verify that miR-223 targeted ABCB1 3'UTR directly, and miR-223 downregulated ABCB1 at both mRNA and protein levels. Finally, we found that the over-expression of miR-223 increased the HCC cell sensitivity to anticancer drugs, and the inhibition of miR-223 had the opposite effect. Importantly, the over-expression or silencing of ABCB1 can rescue the cell response to the anticancer drugs mediated by miR-223 over-expression or inhibition, respectively. In conclusion, our findings indicated that miR-223 played an important role in the regulation of MDR mediated by ABCB1, and it suggests that miR-223 may be considered as a therapeutic biomarker for HCC patients who had MDR problems induced by high expression of ABCB1.

Dissecting functions of KATANIN and WRINKLED1 in cotton fiber development by virus-induced gene silencing.

Most of the world's natural fiber comes from cotton (Gossypium spp.), which is an important crop worldwide. Characterizing genes that regulate cotton yield and fiber quality is expected to benefit the sustainable production of natural fiber. Although a huge number of expressed sequence tag sequences are now available in the public database, large-scale gene function analysis has been hampered by the low-efficiency process of generating transgenic cotton plants. Tobacco rattle virus (TRV) has recently been reported to trigger virus-induced gene silencing (VIGS) in cotton leaves. Here, we extended the utility of this method by showing that TRV-VIGS can operate in reproductive organs as well. We used this method to investigate the function of KATANIN and WRINKLED1 in cotton plant development. Cotton plants with suppressed KATANIN expression produced shorter fibers and elevated weight ratio of seed oil to endosperm. By contrast, silencing of WRINKLED1 expression resulted in increased fiber length but reduced oil seed content, suggesting the possibility to increase fiber length by repartitioning carbon flow. Our results provide evidence that the TRV-VIGS system can be used for rapid functional analysis of genes involved in cotton fiber development.

Development of marker-free transgenic Jatropha plants with increased levels of seed oleic acid.

BACKGROUND: Jatropha curcas is recognized as a new energy crop due to the presence of the high amount of oil in its seeds that can be converted into biodiesel. The quality and performance of the biodiesel depends on the chemical composition of the fatty acids present in the oil. The fatty acids profile of the oil has a direct impact on ignition quality, heat of combustion and oxidative stability. An ideal biodiesel composition should have more monounsaturated fatty acids and less polyunsaturated acids. Jatropha seed oil contains 30% to 50% polyunsaturated fatty acids (mainly linoleic acid) which negatively impacts the oxidative stability and causes high rate of nitrogen oxides emission. RESULTS: The enzyme 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine delta 12-desaturase (FAD2) is the key enzyme responsible for the production of linoleic acid in plants. We identified three putative delta 12 fatty acid desaturase genes in Jatropha (JcFAD2s) through genome-wide analysis and downregulated the expression of one of these genes, JcFAD2-1, in a seed-specific manner by RNA interference technology. The resulting JcFAD2-1 RNA interference transgenic plants showed a dramatic increase of oleic acid (> 78%) and a corresponding reduction in polyunsaturated fatty acids (< 3%) in its seed oil. The control Jatropha had around 37% oleic acid and 41% polyunsaturated fatty acids. This indicates that FAD2-1 is the major enzyme responsible for converting oleic acid to linoleic acid in Jatropha. Due to the changes in the fatty acids profile, the oil of the JcFAD2-1 RNA interference seed was estimated to yield a cetane number as high as 60.2, which is similar to the required cetane number for conventional premium diesel fuels (60) in Europe. The presence of high seed oleic acid did not have a negative impact on other Jatropha agronomic traits based on our preliminary data of the original plants under greenhouse conditions. Further, we developed a marker-free system to generate the transgenic Jatropha that will help reduce public concerns for environmental issues surrounding genetically modified plants. CONCLUSION: In this study we produced seed-specific JcFAD2-1 RNA interference transgenic Jatropha without a selectable marker. We successfully increased the proportion of oleic acid versus linoleic in Jatropha through genetic engineering, enhancing the quality of its oil.

A critical domain of the Cucumber mosaic virus 2b protein for RNA silencing suppressor activity.

Alignment of Cucumber mosaic virus (CMV) 2b protein sequences from two CMV subgroups revealed two highly variable regions. To examine contributions of variable sequence domains to the suppressor activity, we performed a comparative study between 2b proteins of a subgroup I strain (SD-CMV) and a subgroup II strain (Q-CMV). Here we show that the suppressor activity of SD2b is stronger than that of Q2b and that a domain existent in SD2b but absent in Q2b is a major determinant of the suppressor activity of SD2b. We further show that the same domain is responsible for inhibition of Nicotiana benthamiana AGO4-1 transcription. Our results implicate AGO4 as a mediator for CMV 2b to suppress systemic silencing and DNA methylation.

Identification of a movement protein of rice yellow stunt rhabdovirus.

Rice yellow stunt rhabdovirus (RYSV) encodes seven genes in its negative-sense RNA genome in the order 3'-N-P-3-M-G-6-L-5'. The existence of gene 3 in the RYSV genome and an analogous gene(s) of other plant rhabdoviruses positioned between the P and M genes constitutes a unique feature for plant rhabdoviruses that is distinct from animal-infecting rhabdoviruses in which the P and M genes are directly linked. However, little is known about the function of these extra plant rhabdovirus genes. Here we provide evidence showing that the protein product encoded by gene 3 of RYSV, P3, possesses several properties related to a viral cell-to-cell movement protein (MP). Analyses of the primary and secondary protein structures suggested that RYSV P3 is a member of the "30K" superfamily of viral MPs. Biolistic bombardment transcomplementation experiments demonstrated that RYSV P3 can support the intercellular movement of a movement-deficient potexvirus mutant in Nicotiana benthamiana leaves. In addition, Northwestern blot analysis indicated that the RYSV P3 protein can bind single-stranded RNA in vitro, a common feature of viral MPs. Finally, glutathione S- transferase pull-down assays revealed a specific interaction between the RYSV P3 protein and the N protein which is a main component of the ribonucleocapsid, a subviral structure believed to be involved in the intercellular movement of plant rhabdoviruses. Together, these data suggest that RYSV P3 is likely a MP of RYSV, thus representing the first example of characterized MPs for plant rhabdoviruses.