Phytoalexin sakuranetin attenuates endocytosis and enhances resistance to rice blast.

Phytoalexin sakuranetin functions in resistance against rice blast. However, the mechanisms underlying the effects of sakuranetin remains elusive. Here, we report that rice lines expressing resistance (R) genes were found to contain high levels of sakuranetin, which correlates with attenuated endocytic trafficking of plasma membrane (PM) proteins. Exogenous and endogenous sakuranetin attenuates the endocytosis of various PM proteins and the fungal effector PWL2. Moreover, accumulation of the avirulence protein AvrCO39, resulting from uptake into rice cells by Magnaporthe oryzae, was reduced following treatment with sakuranetin. Pharmacological manipulation of clathrin-mediated endocytic (CME) suggests that this pathway is targeted by sakuranetin. Indeed, attenuation of CME by sakuranetin is sufficient to convey resistance against rice blast. Our data reveals a mechanism of rice against M. oryzae by increasing sakuranetin levels and repressing the CME of pathogen effectors, which is distinct from the action of many R genes that mainly function by modulating transcription.

Salicylic acid inhibits rice endocytic protein trafficking mediated by OsPIN3t and clathrin to affect root growth.

Salicylic acid (SA) plays important roles in different aspects of plant development, including root growth, where auxin is also a major player by means of its asymmetric distribution. However, the mechanism underlying the effect of SA on the development of rice roots remains poorly understood. Here, we show that SA inhibits rice root growth by interfering with auxin transport associated with the OsPIN3t- and clathrin-mediated gene regulatory network (GRN). SA inhibits root growth as well as Brefeldin A-sensitive trafficking through a non-canonical SA signaling mechanism. Transcriptome analysis of rice seedlings treated with SA revealed that the OsPIN3t auxin transporter is at the center of a GRN involving the coat protein clathrin. The root growth and endocytic trafficking in both the pin3t and clathrin heavy chain mutants were SA insensitivity. SA inhibitory effect on the endocytosis of OsPIN3t was dependent on clathrin; however, the root growth and endocytic trafficking mediated by tyrphostin A23 (TyrA23) were independent of the pin3t mutant under SA treatment. These data reveal that SA affects rice root growth through the convergence of transcriptional and non-SA signaling mechanisms involving OsPIN3t-mediated auxin transport and clathrin-mediated trafficking as key components.

Colonization of endophyte Acremonium sp. D212 in Panax notoginseng and rice mediated by auxin and jasmonic acid.

Endophytic fungi can be beneficial to plant growth. However, the molecular mechanisms underlying colonization of Acremonium spp. remain unclear. In this study, a novel endophytic Acremonium strain was isolated from the buds of Panax notoginseng and named Acremonium sp. D212. The Acremonium sp. D212 could colonize the roots of P. notoginseng, enhance the resistance of P. notoginseng to root rot disease, and promote root growth and saponin biosynthesis in P. notoginseng. Acremonium sp. D212 could secrete indole-3-acetic acid (IAA) and jasmonic acid (JA), and inoculation with the fungus increased the endogenous levels of IAA and JA in P. notoginseng. Colonization of the Acremonium sp. D212 in the roots of the rice line Nipponbare was dependent on the concentration of methyl jasmonate (MeJA) (2-15 µmol/L) and 1-naphthalenacetic acid (NAA) (10-20 µmol/L). Moreover, the roots of the JA signaling-defective coi1-18 mutant were colonized by Acremonium sp. D212 to a lesser degree than those of the wild-type Nipponbare and miR393b-overexpressing lines, and the colonization was rescued by MeJA but not by NAA. It suggests that the cross-talk between JA signaling and the auxin biosynthetic pathway plays a crucial role in the colonization of Acremonium sp. D212 in host plants.

A four-dimensional potential energy surface for the Ar-D2O van der Waals complex: Bending normal coordinate dependence.

In this paper, we report a four-dimensional potential energy surface (PES) of the Ar-D2O complex. The ab initio calculations are carried out by the coupled-cluster singles and doubles level with noniterative inclusion of connected triples [CCSD(T)] method with a large basis set supplemented with bond functions. The PES includes explicit dependence on the ν2 bending normal coordinate of Q2 the D2O molecule. Two vibrationally averaged PESs with D2O molecule in its ground and first ν2 excited vibrational states are generated by integrating over the Q2 normal coordinate. Based on these two PESs, the bound state energies are determined and used in the infrared spectra prediction. The theoretical frequencies for 104 infrared transitions of Π1(11)(ν2 = 1)←Σ0(00), Σ1(11)(ν2 = 1)←Σ0(00), Π1(10)(ν2 = 1)←Σ0(01), and Π1(01)(ν2 = 1)←Σ1(01) of Ar-D2O complex are in good agreement with the available experimental values.

Low energy collisions of CN(X2Σ+) with He in magnetic fields.

A theoretical investigation of the He-CN((2)Σ(+)) complex is presented. We perform ab initio calculations of the interaction potential energy surface and carry out accurate calculations of bound energy levels of the complex including the molecular fine structure. We find the potential has a shallow minimum and supports seven and nine bound levels in complex with (3)He and (4)He, respectively. Based on the potential the quantum scattering calculation is then implemented for elastic and inelastic cross sections of the magnetically trappable low-field-seeking state of CN((2)Σ(+)) in collision with (3)He atom. The cold collision properties and the influence of the external magnetic field as well as the effect of the uncertainty of interaction potential on the collisionally induced Zeeman relaxation are explored and discussed in detail. The ratios of elastic to inelastic cross sections are large over a wide range of collision energy, magnetic field, and scaling factor of the potential, suggesting helium buffer gas loading and cooling of CN in a magnetic trap is a good prospect.

Ab initio potential energy surface and bound states for the Kr-OCS complex.

The first ab initio potential energy surface of the Kr-OCS complex is developed using the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)]. The mixed basis sets, aug-cc-pVTZ for the O, C, and S atom, and aug-cc-pVQZ-PP for the Kr atom, with an additional (3s3p2d1f) set of midbond functions are used. A potential model is represented by an analytical function whose parameters are fitted numerically to the single point energies computed at 228 configurations. The potential has a T-shaped global minimum and a local linear minimum. The global minimum occurs at R = 7.146 a(0), θ = 105.0° with energy of -270.73 cm(-1). Bound state energies up to J = 9 are calculated for three isotopomers (82)Kr-OCS, (84)Kr-OCS, and (86)Kr-OCS. Analysis of the vibrational wavefunctions and energies suggests the complex can exist in two isomeric forms: T-shaped and quasi-linear. The calculated transition frequencies and spectroscopic constants of the three isotopomers are in good agreement with the experimental values.

A first-principles study of K adsorption on Pb(111).

Ab initio total-energy density functional theory calculations with supercell models have been employed to investigate the R30 degrees and (2 x 2) structures of K on the Pb(111) surface. Four "on-surface" sites and a substitutional site were considered. The calculations showed that the substitutional site is more stable than all the on-surface sites, due to its low vacancy formation energy. The calculated R30 degrees geometry agrees well with the LEED results. The density-of-states analysis indicates that the K atom loses part of its loosely bound valence s electron. From the electron density distributions, it was found that the lowering of the work function after the substitutional adsorption can be attributed to the dipole moment, associated with the positively polarized adsorbate atom that is characterized by charge depletion from the K vacuum sides and charge accumulation in the region between K and Pb atoms. Our results indicate that the bonding of K with the Pb(111) surface has a mixed ionic and metallic bond character.