AXR1 modulates trichome morphogenesis through mediating ROP2 stability in Arabidopsis.

Cell differentiation and morphogenesis are crucial for the establishment of diverse cell types and organs in multicellular organisms. Trichome cells offer an excellent paradigm for dissecting the regulatory mechanisms of plant cell differentiation and morphogenesis due to their unique growth characteristics. Here, we report the isolation of an Arabidopsis mutant, aberrantly branched trichome 3-1 (abt3-1), with a reduced trichome branching phenotype. Positional cloning and molecular complementation experiments confirmed that abt3-1 is a new mutant allele of Auxin resistant 1 (AXR1), which encodes the N-terminal half of ubiquitin-activating enzyme E1 and functions in auxin signaling pathway. Meanwhile, we found that transgenic plants expressing constitutively active version of ROP2 (CA-ROP2) caused a reduction of trichome branches, resembling that of abt3-1. ROP2 is a member of Rho GTPase of plants (ROP) family, serving as versatile signaling switches involved in a range of cellular and developmental processes. Our genetic and biochemical analyses showed AXR1 genetically interacted with ROP2 and mediated ROP2 protein stability. The loss of AXR1 aggravated the trichome defects of CA-ROP2 and induced the accumulation of steady-state ROP2. Consistently, elevated AXR1 expression levels suppressed ROP2 expression and partially rescued trichome branching defects in CA-ROP2 plants. Together, our results presented a new mutant allele of AXR1, uncovered the effects of AXR1 and ROP2 during trichome development, and revealed a pathway of ROP2-mediated regulation of plant cell morphogenesis in Arabidopsis.

Substrate carrier concentration dependent plasmon-phonon coupled modes at the interface between graphene and semiconductors.

The coupled modes between graphene plasmons and surface phonons of a semiconductor substrate are investigated, which can be efficiently controlled by carrier injection of the substrate. A new physical mechanism on tuning plasmon-phonon coupled modes (PPCMs) is proposed due to the fact that the energy and lifetime of substrate surface phonons depend a lot on the carrier concentration. Specifically, the change of dispersion and lifetime of PPCMs can be controlled by the carrier concentration of the substrate. The energy of PPCMs for a given momentum increases as the carrier concentration of the substrate increases. On the other hand, the momentum of PPCMs for a given energy decreases when the carrier concentration of the substrate increases. The lifetime of PPCMs is always larger than the intrinsic lifetime of graphene plasmons without plasmon-phonon coupling.

Nanofocusing of the free-space optical energy with plasmonic Tamm states.

To achieve extreme electromagnetic enhancement, we propose a plasmonic Tamm states (PTSs) configuration based on the metal-insulator-metal Bragg reflector, which is realized by periodically modulating the width of the insulator. Both the thick (2D) and thin (3D) structures are discussed. Through optimization performed by the impedance-based transfer matrix method and the finite difference time domain method, we find that both the electric field and magnetic field intensities can be increased by three orders of magnitude. The field-enhancement inside the PTSs configuration is not limited to extremely sharp waveguide terminal, which can greatly reduce processing difficulties.