KATANIN-dependent mechanical properties of the stigmatic cell wall mediate the pollen tube path in Arabidopsis

Successful fertilization in angiosperms depends on the proper trajectory of pollen tubes through the pistil tissues to reach the ovules. Pollen tubes first grow within the cell wall of the papilla cells, applying pressure to the cell. Mechanical forces are known to play a major role in plant cell shape by controlling the orientation of cortical microtubules (CMTs), which in turn mediate deposition of cellulose microfibrils (CMFs). Here, by combining imaging, genetic and chemical approaches, we show that isotropic reorientation of CMTs and CMFs in aged Col-0 and katanin1-5 (ktn1-5) papilla cells is accompanied by a tendency of pollen tubes to coil around the papillae. We show that this coiled phenotype is associated with specific mechanical properties of the cell walls that provide less resistance to pollen tube growth. Our results reveal an unexpected role for KTN1 in pollen tube guidance on the stigma by ensuring mechanical anisotropy of the papilla cell wall.

Mechanical properties of the stigmatic cell wall mediate pollen tube path in Arabidopsis

ABSTRACTSuccessful fertilization in angiosperms depends on the proper trajectory of pollen tubes through the pistil tissues to reach the ovules. Pollen tubes first grow within the cell wall of the papilla cells, applying pressure to the cell. Mechanical forces are known to play a major role in plant cell shape by controlling the orientation of cortical microtubules (CMTs), which in turn mediate deposition of cellulose microfibrils (CMFs). Here, by combining cell imaging and genetic approaches, we show that isotropic reorientation of CMTs and CMFs in aged and katanin1-5 (ktn1-5) papilla cells is accompanied by a tendency of pollen tubes to coil around the papillae. Furthermore, we uncover that aged and ktn1-5 papilla cells have a softer cell wall and provide less resistance to pollen tube growth. Our results reveal an unexpected role for KTN1 in pollen tube guidance by ensuring mechanical anisotropy of the papilla cell wall.

Solid and fluid segments within the same molecule of stratum corneum ceramide lipid

The outer layer of the skin, stratum corneum (SC) is an efficient transport barrier and it tolerates mechanical deformation. At physiological conditions, the majority of SC lipids are solid, while the presence of a small amount of fluid lipids is considered crucial for SC barrier and material properties. Here we use solid-state and diffusion nuclear magnetic resonance to characterize the composition and molecular dynamics of the fluid lipid fraction in SC model lipids, focusing on the role of the essential SC lipid CER EOS, which is a ceramide esterified omega-hydroxy sphingosine linoleate with very long chain. We show that both rigid and mobile structures are present within the same CER EOS molecule, and that the linoleate segments undergo fast isotropic reorientation while exhibiting extraordinarily slow self-diffusion. The characterization of this unusual self-assembly in SC lipids provides deepened insight into the molecular arrangement in the SC extracellular lipid matrix and the role of CER EOS linoleate in the healthy and diseased skin.

Investigation of New Ionic Plastic Crystals in Tetraalkylammonium Tetrabuthylborate

New plastic crystals of NEt3PrBBu4 and NEt2Pr2BBu4 were formed in a new region of ionic plastic crystal. In this area, globular cations and anions are assembled by weak interactions. Differential scanning calorimeter (DSC) measurements of these salts showed a low entropy change of 19:6 and 14:0 JK-1 mol-1 at each melting point, respectively. On the basis of solid-state 1H and 13C nuclear magnetic resonance (NMR) spectra and electrical conductivity measurements, isotropic reorientation and ion transfer of globular cations and anions were detected in these crystals. The other compounds of NEtxMe(4-x)BBu4 (x = 1 - 3) showed tumbling motions and low activation energies of self-diffusion in crystals

Ionic Dynamics in the Ionic Plastic Crystal NH4NO2

Using 1H NMR T1 and T1ρ measurements self-diffusion of NH4 + with an activation energy of (80 ± 10) kJ mol−1 was detected in the highest-temperature phase of NH4NO2 crystals. Narrow 15N NMR spectra of 15NH4NO2 and NH415NO2 revealed that the isotropic reorientation rates of NH4 + and NO2 − ions are rapid in the high-temperature solid phase. These results suggest that the high-temperature phase of NH4NO2 crystals forms an ionic plastic phase.

A solid state 31P NMR study of the synthesis of phosphorus sulfides from PCl3 and H2S in microporous materials

The interaction and reaction of PCl3 and PCl3-H2S mixtures with the microporous materials Silicalite, ALPO-5, NaY, NaX, and NaA have been investigated, with the intention of producing phosphorus sulfide clusters in the pores. A rich chemistry was observed and monitored by solid state 31P NMR. The presence of P4S3, α-P4S5, β-P4S6, and P4S7 inside the NaY α-cages was demonstrated, as well as a new species that is possibly a third geometric isomer of P4S4 with C3v symmetry. 129Xe NMR showed the exclusion of Xe from the micropores by the phosphorus sulfides. Sulfides lower than P4S7 are small enough that they undergo rapid pseudo-isotropic reorientation inside the NaY α-cage. Key words: phosphorus sulfides, intrazeolitic cluster synthesis.

Molecular Motions and Phase Transitions in Solid CH3NH3PbX3 (X = C1, Br, I) as Studied by NMR and NQR

The temperature dependence of 35C1, 81Br, and 127I NQR frequencies and 1Hspin-lattice relaxation times (T1) for CH3NH3PbX3 (X = Cl, Br, I) was measured through the successive phase transitions in these solids. The isotropic reorientation of the CH3NH3 ions takes place in the higher-temperature phases (tetragonal [I4/mcm] and cubic) of the three salts (Ea= 11 kJ mol -1). T1's in the lowest-temperature phases (orthorhombic) indicate that the cations undergo correlated C3-reorientation in the chloride (Ea = 5.45 kJ mol -1)and in the iodide (Ea = 5.80 kJ mol -1, whereas correlated (Ea = 2.40 kJ mol-1) and uncorrected (Ea = 7.50 kJ mol-1) C3- reorientations are excited in the bromide. It is also revealed that the rotational tunneling of the cations governs T1 at lowtemperature region in the orthorhombic phases of these salts

A multinuclear nuclear magnetic resonance study of t-butylthiol

Deuterium nmr lineshapes for polycrystalline samples of (CD3)3CSH and (CH3)3CSD have been investigated between 110 and 200 K. Unlike t-butylchloride-d9 which undergoes line narrowing in three distinctive stages, t-butylthiol-d9 undergoes almost complete motional line narrowing at 120 ± 5 K. Above the solid II ↔ solid I phase transition no quadrupolar splitting is observed, consistent with rapid "isotropic" reorientation in the solid I phase.An analysis of the 2H and 13C spin–lattice relaxation times of (CD3)3CSH, (CH3)3CSD and unlabelled t-butylthiol in both liquid and solid phases is also reported. The rotational correlation time is observed to decrease by an order of magnitude at the solid II ↔ solid I transition and to increase slightly at the melting point. Deuterium T1s in solids III and IV of the labelled species indicate abrupt changes at the phase transitions and motion slower than ω0−1 in solid IV.