These authors contributed equally to this work. SUMMARYIn Arabidopsis, anthocyanin biosynthesis is controlled by a MYB-bHLH-WD40 (MBW) transcriptional activator complex. The MBW complex activates the transcription of late biosynthesis genes in the flavonoid pathway, leading to the production of anthocyanins. A similar MBW complex regulates epidermal cell fate by activating the transcription of GLABRA2 (GL2), a homeodomain transcription factor required for trichome formation in shoots and non-hair cell formation in roots. Here we provide experimental evidence to show that GL2 also plays a role in regulating anthocyanin biosynthesis in Arabidopsis. From an activation-tagged mutagenized population of Arabidopsis plants, we isolated a dominant, gain-of-function mutant with reduced anthocyanins. Molecular cloning revealed that this phenotype is caused by an elevated expression of GL2, thus the mutant was named gl2-1D. Consistent with the view that GL2 acts as a negative regulator of anthocyanin biosynthesis, gl2-1D seedlings accumulated less whereas gl2-3 seedlings accumulated more anthocyanins in response to sucrose. Gene expression analysis indicated that expression of late, but not early, biosynthesis genes in the flavonoid pathway was dramatically reduced in gl2-1D but elevated in gl2-3 mutants. Further analysis showed that expression of some MBW component genes involved in the regulation of late biosynthesis genes was reduced in gl2-1D but elevated in gl2-3 mutants, and chromatin immunoprecipitation results indicated that some MBW component genes are targets of GL2. We also showed that GL2 functions as a transcriptional repressor. Taken together, these results indicate that GL2 negatively regulates anthocyanin biosynthesis in Arabidopsis by directly repressing the expression of some MBW component genes.

GLABRA1 (GL1) is an R2R3 MYB transcription factor that regulates trichome formation in Arabidopsis by interacting with the bHLH transcription factor GLABRA3 (GL3) or ENHANCER OF GL3 (EGL3). The conserved [D/E]L×2 [R/K]×3L×6L×3R amino acid signature in the R3 domain of MYB proteins has been shown to be required for the interaction of MYBs with R/B-like bHLH transcription factors. By using genetic and molecular analyses, we show that the glabrous phenotype in the nph4-1 mutant is caused by a single nucleotide mutation in the GL1 gene, generating a Ser to Phe substitution (S92F) in the conserved [D/E]L×2[R/K]×3L×6L×3R amino acid signature of GL1. Activation of the integrated GL2p:GUS reporter gene in protoplasts by cotransfection of GL1 and GL3 or EGL3 was abolished by this GL1-S92F substitution. However, GL1-S92F interacted successfully with GL3 or EGL3 in protoplast transfection assays. Unlike VPGL1GL3, the fusion protein VPGL1-S92FGL3 failed to activate the integrated GL2p:GUS reporter gene in transfected protoplasts. These results suggested that the S92 in the conserved [D/E]L×2 [R/K]×3L×6L×3R amino acid signature of GL1 is not essential for the interaction of GL1 and GL3, but may play a role in the binding of GL1 to the promoters of its target genes.

Plant hormone abscisic acid (ABA) plays a crucial role in modulating plant responses to environmental stresses. Basic helix-loop-helix (bHLH) transcription factors are one of the largest transcription factor families that regulate multiple aspects of plant growth and development, as well as of plant metabolism in Arabidopsis. Several bHLH transcription factors have been shown to be involved in the regulation of ABA signaling. We report here the characterization of bHLH129, a bHLH transcription factor in Arabidopsis. We found that the expression level of bHLH129 was reduced in response to exogenously applied ABA, and elevated in the ABA biosynthesis mutant aba1-5. Florescence observation of transgenic plants expressing bHLH129-GFP showed that bHLH129 was localized in the nucleus, and transient expression of bHLH129 in protoplasts inhibited reporter gene expression. When expressed in Arabidopsis under the control of the 35S promoter, bHLH129 promoted root elongation, and the transgenic plants were less sensitivity to ABA in root elongation assays. Quantitative RT-PCR results showed that ABA response of several genes involved in ABA signaling, including ABI1, SnRK2.2, SnRK2.3 and SnRK2.6 were altered in the transgenic plants overexpressing bHLH129. Taken together, our study suggests that bHLH129 is a transcription repressor that negatively regulates ABA response in Arabidopsis.

The emergence of multidrug-resistant-bacteria (MDRB) infection poses a major burden to modern healthcare. Early detection in the bloodstream and a new strategy development for MDRB infection treatment without antibiotics are clinically significant to save millions of lives every year. To tackle the MDRB challenge, the current manuscript reports the design of "multifunctional nanoplatforms" consisting of a magnetic core-plasmonic shell nanoparticle, a methylene blue-bound aptamer, and an MDRB Salmonella DT104 specific antibody. The reported "multifunctional nanoplatform" is capable of targeted separation from a blood sample and sensing and multimodal therapeutic killing of MDRB. Experimental data using an MDRB-infected whole-blood sample show that nanoplatforms can be used for selective magnetic separation and fluorescence imaging. In vitro light-triggered photodestruction of MDRB, using combined photodynamic and photothermal treatment, shows that the multimodal treatment regime can enhance MDRB killing significantly. We discussed the possible mechanisms on combined synergistic therapy for killing MDRB. The "multifunctional nanoplatform" reported in this manuscript has great potential for the imaging and combined therapy of MDRB in clinical settings.

For several decades, cancer has been one of the most life-threatening diseases. For enhancing anticancer efficiency with minimum side effects, combination therapy is envisioned. The current manuscript reports for the first time the development of a methylene blue (MB) bound nanoplatform, which is capable of delivering targeted diagnostic and combined synergistic photothermal and photodynamic treatment of cancer. Experimental data found that, once the nanoparticle binds with the target cell surface, it can detect LNCaP human prostate cancer cell selectively using fluorescence imaging. Our result shows that the therapeutic actions can be controlled with external NIR light. No cytotoxicity was observed in the absence of NIR light. Targeted photodynamic and photothermal treatment using 785 nm NIR light indicates that the multimodal treatment enhances the possibility of destroying LNCaP prostate cancer cells in vitro dramatically. We discuss the operating principle for the targeted imaging and possible mechanisms for combined therapeutic actions. Our experimental data show that NIR light activated combined therapy for cancer may become a highly effective treatment procedure in clinical settings.