The phytochrome-interacting factor genes PIF1 and PIF4 are functionally diversified due to divergence of promoters and proteins.

Phytochrome-interacting factors (PIFs) are basic helix-loop-helix transcription factors that regulate light responses downstream of phytochromes. In Arabidopsis (Arabidopsis thaliana), eight PIFs (PIF1-8) regulate light responses, either redundantly or distinctively. Distinctive roles of PIFs may be attributed to differences in mRNA expression patterns governed by promoters or variations in molecular activities of proteins. However, elements responsible for the functional diversification of PIFs have yet to be determined. Here, we investigated the role of promoters and proteins in the functional diversification of PIF1 and PIF4 by analyzing transgenic lines expressing promoter-swapped PIF1 and PIF4, as well as chimeric PIF1 and PIF4 proteins. For seed germination, PIF1 promoter played a major role, conferring dominance to PIF1 gene with a minor contribution from PIF1 protein. Conversely, for hypocotyl elongation under red light, PIF4 protein was the major element conferring dominance to PIF4 gene with the minor contribution from PIF4 promoter. In contrast, both PIF4 promoter and PIF4 protein were required for the dominant role of PIF4 in promoting hypocotyl elongation at high ambient temperatures. Together, our results support that the functional diversification of PIF1 and PIF4 genes resulted from contributions of both promoters and proteins, with their relative importance varying depending on specific light responses.

Epidermal phyB requires RRC1 to promote light responses by activating the circadian rhythm.

Phytochrome B (phyB) expressed in the epidermis is sufficient to promote red light responses, including the inhibition of hypocotyl elongation and hypocotyl negative gravitropism. Nonetheless, the downstream mechanism of epidermal phyB in promoting light responses had been elusive. Here, we mutagenized the epidermis-specific phyB-expressing line (MLB) using ethyl methanesulfonate (EMS) and characterized a novel mutant allele of RRC1 (rrc1-689), which causes reduced epidermal phyB-mediated red light responses. The rrc1-689 mutation increases the alternative splicing of major clock gene transcripts, including PRR7 and TOC1, disrupting the rhythmic expression of the entire clock and clock-controlled genes. Combined with the result that MLB/prr7 exhibits the same red-hyposensitive phenotypes as MLB/rrc1-689, our data support that the circadian clock is required for the ability of epidermal phyB to promote light responses. We also found that, unlike phyB, RRC1 preferentially acts in the endodermis to maintain the circadian rhythm by suppressing the alternative splicing of core clock genes. Together, our results suggest that epidermal phyB requires RRC1 to promote light responses by activating the circadian rhythm in Arabidopsis thaliana.

Multiblock Copolymers for Recycling Polyethylene-Poly(ethylene terephthalate) Mixed Waste.

Plastic pollution is one of the most pressing global environmental issues we face today, in part due to the continued rise in production and use of disposable plastic products. Polyolefins and polyesters are two of the most prevalent polymers in the world accounting for ∼80% of total nonfiber plastic production. Recycling, despite being intrinsically environmentally friendly and sometimes economically viable, remains at a surprisingly low level (<9% in the U.S.) with most plastic waste ending up in landfills. One reason for this low rate of recycling stems from the challenge of recycling mixed waste streams and multicomponent plastics. In mixed waste streams, physical presorting of components prior to recycling requires significant effort, which translates to added cost. For multicomponent plastics (e.g., multilayer films such as food wrappers), the individual plastic components cannot be efficiently physically separated, and they are immiscible with poor interfacial adhesion when melt reprocessed. Thus, direct recycling of mixed plastics by melt reprocessing results in products that lack desired end-use properties. In this study, we describe the synthesis of novel poly(ethylene terephthalate)-polyethylene multiblock copolymers (PET-PE MBCPs) and evaluate their utility as adhesive tie layers in multilayer films and compatibilizer additives for melt reprocessed blends. PET and PE are targeted because they are two of the most prevalent commercial polymers in the world and are high volume waste streams. The work described here demonstrates two key findings. First, the PET-PE MBCPs serve as effective adhesive tie layers between neat PET/PE films with adhesive strength comparable to that of commercially available adhesives. Second, PET/PE (80/20 wt %) blends containing ∼0.5 wt % PET-PE MBCP were melt mixed to mimic recycling mixed plastic waste, and they were found to exhibit mechanical properties better than neat PET. Overall, this study demonstrates that PET-PE MBCPs could significantly enhance the ability to recycle PET/PE mixed waste streams by serving the role as both an adhesive promoting layer and a compatibilizer additive.

The epidermis coordinates thermoresponsive growth through the phyB-PIF4-auxin pathway.

In plants, an elevation in ambient temperature induces adaptive morphological changes including elongated hypocotyls, which is predominantly regulated by a bHLH transcription factor, PIF4. Although PIF4 is expressed in all aerial tissues including the epidermis, mesophyll, and vascular bundle, its tissue-specific functions in thermomorphogenesis are not known. Here, we show that epidermis-specific expression of PIF4 induces constitutive long hypocotyls, while vasculature-specific expression of PIF4 has no effect on hypocotyl growth. RNA-Seq and qRT-PCR analyses reveal that auxin-responsive genes and growth-related genes are highly activated by epidermal, but not by vascular, PIF4. Additionally, inactivation of epidermal PIF4 or auxin signaling, and overexpression of epidermal phyB suppresses thermoresponsive growth, indicating that epidermal PIF4-auxin pathways are essential for the temperature responses. Further, we show that high temperatures increase both epidermal PIF4 transcription and the epidermal PIF4 DNA-binding ability. Taken together, our study demonstrates that the epidermis regulates thermoresponsive growth through the phyB-PIF4-auxin pathway.

Detection of Matrix Metalloproteinase Activity by Bioluminescence via Intein-Mediated Biotinylation of Luciferase.

We report bioluminescence analysis of matrix metalloproteinase (MMP) activity in biological substances using a surface-bound luciferase probe. Intein-fused luciferase protein enables site-specific biotinylation of luciferase in the presence of N-terminus cysteine-biotin via intein-mediated splicing process, resulting in a strong association with high bioluminescence signal onto a NeutrAvidin-coated surface. When the peptide substrate for MMP-7 was inserted into a region between luciferase and intein, the biotinylated probe detected MMP-7 activity by cleaving the peptide, and surface-induced bioluminescence signal was strongly reduced in the MMP-secreted media or mouse tissue extracts, compared with that in MMP-deficient control set. Our approach is anticipated to be useful for generating biotinylated proteins and for their applications in diagnosing MMP activity in human diseases.

Structural transitions and guest/host complexing of liquid crystal helical nanofilaments induced by nanoconfinement.

A lamellar liquid crystal (LC) phase of certain bent-core mesogenic molecules can be grown in a manner that generates a single chiral helical nanofilament in each of the cylindrical nanopores of an anodic aluminum oxide (AAO) membrane. By introducing guest molecules into the resulting composite chiral nanochannels, we explore the structures and functionality of the ordered guest/host LC complex, verifying the smectic-like positional order of the fluidic nematic LC phase, which is obtained by the combination of the LC organization and the nanoporous AAO superstructure. The guest nematic LC 4'-n-pentyl-4-cyanobiphenyl is found to form a distinctive fluid layered ordered LC complex at the nanofilament/guest interface with the host 1,3-phenylene bis[4-(4-nonyloxyphenyliminomethyl)benzoate], where this interface contacts the AAO cylinder wall. Filament growth form is strongly influenced by mixture parameters and pore dimensions.

Airflow-aligned helical nanofilament (B4) phase in topographic confinement.

We investigated a controlled helical nanofilament (HNF: B4) phase under topographic confinement with airflow that can induce a shear force and temperature gradient on the sample. The resulting orientation and ordering of the B4 phase in this combinational effort was directly investigated using microscopy. The structural freedom of the complex B7 phase, which is a higher temperature phase than the B4 phase, can result in relatively complex microscopic arrangements of HNFs compared with the B4 phase generated from the simple layer structure of the B2 phase. This interesting chiral/polar nanofilament behaviour offers new opportunities for further exploration of the exotic physical properties of the B4 phase.

Linkage-length dependent structuring behaviour of bent-core molecules in helical nanostructures.

We studied the correlation between the molecular structure and the formation of helical nanofilaments (HNFs) of bent-core dimeric molecules with varying linkage lengths. To obtain precise structural data, a single domain of HNFs was prepared under physical confinement using porous 1D nanochannels, made up of anodic aluminium oxide films. Electron microscopy and grazing incidence X-ray diffraction were used to elucidate the linkage length-dependent formation of HNFs.

Photomodulated Supramolecular Chirality in Achiral Photoresponsive Rodlike Compounds Nanosegregated from the Helical Nanofilaments of Achiral Bent-Core Molecules.

We prepared a nonchiral mixture of achiral bent-core molecules and photoresponsive rodlike liquid crystalline (LC) molecules. With the help of the isothermal photochemical nematic (N)-isotropic (Iso) phase transition of the photoresponsive rodlike LC molecules, the corresponding phase transition from a dark conglomerate BX phase to another distinguishable dark conglomerate B4 phase took place in the mixture. A large circular dichroism (CD) signal originating from supramolecular chirality was detected in the initial BX phase. On the other hand, the detected CD signal was decreased in the B4 phase after UV irradiation. Interestingly, the decreased CD signal could be reverted to the initial CD signal with visible irradiation. This chiroptical process revealed in this work was stable and reversible and thus opens up the possibility of practical applications such as rewritable optical storage.

Nucleation and growth of a helical nanofilament (B4) liquid-crystal phase confined in nanobowls.

The B4 helical nanofilament (HNF) liquid crystal (LC) phase is a three-dimensional (3D) helical structure composed of 2D smectic layers. Because of the complex shape of the HNF phase, it is difficult to understand the generation mechanism of HNFs in the bulk as well as in the thin-film condition. Here, we directly investigated the nucleation and growth of HNFs in nanobowls. A combination of electron microscopy and X-ray diffraction was used to reveal the transitional surface structures, in which barrel-like structures as well as short HNFs with random handedness were observed, depending on the LC film thickness. These results will be useful in achieving a better understanding of thin film structures of complex chiral structures in soft matter.

Multidimensional Helical Nanostructures in Multiscale Nanochannels.

We have investigated the various morphological changes of helical nanofilament (HNF; B4) phases in multiscale nanochannels made of porous anodic aluminum oxide (AAO) film. Single or multihelical structures could be manipulated depending on the AAO pore size and the higher-temperature phase of each molecule. Furthermore, the nanostructures of HNFs affected by the chemical affinity between the molecule and surface were drastically controlled in surface-modified nanochannels. These well-controlled hierarchical helical structures that have multidimensions can be a promising tool for the manipulation of chiral pores or the nonlinear optical applications.

Multistep hierarchical self-assembly of chiral nanopore arrays.

A series of simple hierarchical self-assembly steps achieve self-organization from the centimeter to the subnanometer-length scales in the form of square-centimeter arrays of linear nanopores, each one having a single chiral helical nanofilament of large internal surface area and interfacial interactions based on chiral crystalline molecular arrangements.

Solvent-free directed patterning of a highly ordered liquid crystalline organic semiconductor via template-assisted self-assembly for organic transistors.

Highly ordered organic semiconductor micropatterns of the liquid-crystalline small molecule 2,7-didecylbenzothienobenzothiophene (C10 -BTBT) are fabricated using a simple method based on template-assisted self-assembly (TASA). The liquid crystallinity of C10 -BTBT allows solvent-free fabrication of high-performance printed organic field-effect transistors (OFETs).