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Strigolactones (SLs) play prominent roles in regulating shoot branching and root architecture in model plants. However, their roles in non-model (particularly woody) plants remain unclear. Liriodendron chinense is a timber tree species widely planted in southern China. The outturn percentage and wood quality of L. chinense are greatly affected by the branching characteristics of its shoot, and the rooting ability of the cuttings is key for its vegetative propagation. Here, we isolated and analyzed the function of the MORE AXILLARY GROWTH 1 (LcMAX1) gene, which is involved in L. chinense SL biosynthesis. RT-qPCR showed that LcMAX1 was highly expressed in the roots and axillary buds. LcMAX1 was located in the endoplasmic reticulum (ER) and nucleus. LcMAX1 ectopic expression promoted primary root growth, whereas there were no phenotypic differences in shoot branching between transgenic and wild-type (WT) A. thaliana plants. LcMAX1 overexpression in the max1 mutant restored them to the WT A. thaliana phenotypes. Additionally, AtPIN1, AtPIN2, and AtBRC1 expressions were significantly upregulated in transgenic A. thaliana and the max1 mutant. It was therefore speculated that LcMAX1 promotes primary root growth by regulating expression of auxin transport-related genes in A. thaliana, and LcMAX1 inhibits shoot branching by upregulating expression of AtBRC1 in the max1 mutant. Altogether, these results demonstrated that the root development and shoot branching functions of LcMAX1 were similar to those of AtMAX1. Our findings provide a foundation for obtaining further insights into root and branch development in L. chinense.

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Background Liriodendron chinense is a distinctive ornamental tree species due to its unique leaves and tulip-like flowers. The discovery of genes involved in leaf development and morphogenesis is critical for uncovering the underlying genetic basis of these traits. Genes in the AP2/ERF family are recognized as plant-specific transcription factors that contribute to plant growth, hormone-induced development, ethylene response factors, and stress responses. Results In this study, we identified 104 putative AP2/ERF genes in the recently released L. chinense genome and transcriptome database. In addition, all 104 genes were grouped into four subfamilies, the AP2, ERF, RAV, and Soloist subfamilies. This classification was further supported by the results of gene structure and conserved motif analyses. Intriguingly, after application of a series test of cluster analysis, three AP2 genes, LcERF 94, LcERF 96, and LcERF 98, were identified as tissue-specific in buds based on the expression profiles of various tissues. These results were further validated via RT-qPCR assays and were highly consistent with the STC analysis. We further investigated the dynamic changes of immature leaves by dissecting fresh shoots into seven discontinuous periods, which were empirically identified as shoot apical meristem (SAM), leaf primordia and tender leaf developmental stages according to the anatomic structure. Subsequently, these three candidates were highly expressed in SAM and leaf primordia but rarely in tender leaves, indicating that they were mainly involved in early leaf development and morphogenesis. Moreover, these three genes displayed nuclear subcellular localizations through the transient transformation of tobacco epidermal cells. Conclusions Overall, we identified 104 AP2/ERF family members at the genome-wide level and discerned three candidate genes that might participate in the development and morphogenesis of the leaf primordium in L. chinense.

The unique 'mandarin jacket' leaf shape is the most famous trait ofBased on transcriptome data of leaves at different developmental stages fromIn this study, we found that theThese results suggest that

Background Liriodendron chinense (Hemsl.) Sarg. is an economically and ecologically important deciduous tree species that has been studied for many years. Although the complete L. chinense genome has been sequenced, the gene co-expression modules and tissue-specific genes of L. chinense remain unknown. Results Here, we used the bracts, petals, sepals, stamens, pistils, leaves, and the shoot apex of L. chinense as materials and analysed their gene co-expression modules and tissue-specific genes via hybrid sequencing. We identified 3,032 DEGs between the floral and vegetative tissues and 2,126 tissue-specific genes. By using WGCNA analysis, we identified 13 gene co-expression modules, and KEGG pathway enrichment analysis revealed that tissue-specific genes and genes from different modules were enriched in different pathways. Genes associated with plant defence were highly expressed in the bracts, genes participating in plant hormone signal transduction were highly expressed in the shoot apex, and genes participating in photosynthesis were highly expressed in the leaves, petals and sepals. Moreover, we identified 10 MIKC-type MADS-box genes that were classified as member of the AP3/PI, SVP, SEP, AG/SHP/STK, AGL12, SOC1 and TM8 subfamily. Phylogenetic analysis showed that the expression profiles of these ten genes were consistent with those reported in Arabidopsis and Populus , indicating that these genes are highly conserved evolutionarily and related to floral and vegetative tissue development. The small number of MIKC-type MADS-box genes in L. chinense was probably owing to its incomplete genome annotation. Conclusions In this work, we provided a reference transcriptome for L. chinense research by using hybrid sequencing. We identified 2,126 tissue-specific genes and 3,032 DEGs that contributed greatly to the functional differences between vegetative organs and floral organs. By using WGCNA analysis, 13 gene co-expression modules and 52 hub genes from six co-expression modules of interest were identified. Moreover, we identified 10 MIKC-type MADS-box genes that might be related to the development and growth regulation of floral and vegetative organs. These findings will improve our understanding of gene co-expression, tissue specific genes and flower development model of L. chinense .

Dehydrogenase ascorbic reductase (DHAR) is a critical enzyme involved in resistance to environmental stress. However, few DHAR genes have been identified in woody plants. Liriodendron chinense is a relict tree species of Magnoliaceae. Due to its outstanding ornamental features and fine wood properties, L. chinense is becoming increasingly applied in both timber production and landscaping. A broad ability to adapt is the initial premise of extensive planting of trees; as a result, discovery and functional validation of resistance genes are extremely important. In this study, a putative DHAR gene was isolated from L. chinense. The full-length coding sequence of the LcDHAR gene was cloned and expressed in Escherichia coli. The enzyme was then isolated and purified to investigate its activity and obtain its Michaelis constant. The results showed that the LcDHAR gene encodes a 216-aa protein that contains a complete DHAR domain. Subcellular localization assay revealed LcDHAR a cytoplasmic protein. We further calculated KmGSH and KmDHA values of 1.04 mM and 0.81 mM, respectively, for LcDHAR. Moreover, overexpression of the LcDHAR gene in Arabidopsis thaliana led to a higher content of AsA as well as enhanced salt and drought stress resistance. In addition, the transgenic plants produced leaves at an earlier time and the root length was significantly longer than that of col-0 wild-type line under gradient salt and drought stresses. Taken together, the results of this study reveal that LcDHAR might play a protective role in response to salt and drought stresses and provide a partial framework for LcDHAR gene regulation of DHA and AsA contents in Liriodendron.

This work focuses on the adsorption kinetics of dicynthaurin with lipid monolayers, the effect of peptide adsorption on the structure of the lipid condensed chain lattice, peptide orientation and secondary structure in the adsorbed state. The studies with DPPG as model system revealed strong adsorption and massive incorporation of the peptide into the monolayer. Infrared reflection absorption spectroscopy (IRRAS) experiments showed that the secondary structure of the peptide is maintained upon adsorption. Specular X-ray reflectivity showed the destabilization of the condensed phase of the pure lipid monolayer and revealed a tilted orientation of the long axis of the peptide helix of about 40 degrees from the surface normal. Incorporation of the peptide was found to be pressure dependent, and at high pressure a "squeeze-out" was observed; however, the peptide remained localized to the interface, as suggested by infrared data. These findings were supported by optical fluorescence microscopy measurements which showed the squeeze-out of the peptide on water, but not under physiological conditions. The results suggest that dicynthaurin is able to adsorb to the phosphatidylglycerol-rich inner cytoplasmic membrane of bacteria and alter membrane integrity. To identify and interact with membrane motifs that are characteristic of microbes, but which are absent in eukaryotic cells, might be an intrinsic ability of peptide antibiotics.

This paper reports the first study on the interaction of the antimicrobial peptide dicynthaurin with 1,2-dipalmitoyl-glycerophosphatidyl-glycerol investigated in monolayers at the air-liquid interface. The influence of the peptide on the two-dimensional phase behavior of the negatively charged lipid was elucidated by means of pressure-area isotherm measurements, fluorescence microscopy, and grazing incidence X-ray diffraction measurements. The pure peptide forms a stable monolayer at the air-liquid interface up to 30 mN/m as shown for both the monomeric and the dimeric cynthaurins. The peptide lipid interaction was monitored in isotherm measurements showing a strong adsorption of the peptide and stabilization at the interface promoted by the lipid monolayer. The X-ray diffraction measurements in agreement with fluorescence microscopy studies showed that the peptide destabilizes the condensed chain lattice, leading to a complete fluidization of the condensed lipid phase on physiological buffer. The adsorption of the peptide to the negatively charged lipid monolayer and the fluidization of the condensed chain lattice suggest a direct link to the peptides' ability to expand the bacterial membrane that would be relevant for the in vivo mode of action.

The new hydrophobic azo dye 4-(N-phenyl-N-decylamino)-4'-nitroazobenzene (AzoC10) has been synthesized. It is compared with 4-(N-phenylamino)-4'-nitroazobenzene (Azo) in terms of reactivity (k(iso) of the thermal cis-->trans isomerization, microsecond flash photolysis) and of the solvatochromic behavior (lambda(max) of the trans-isomer, UV/vis absorption), respectively, within membrane mimeting amphiphile microstructures in aqueous solutions of poly(ethylene oxide)(m)-poly(propylene oxide)(n)-poly(ethylene oxide)(m) micelles and of extruded vesicles. The temperature-induced micelle formation and phase transitions in bilayers of vesicles, respectively, caused characteristic discontinuous changes of k(iso) and lambda(max) with temperature. They differ between the two dyes due to their different solubilization sites and different impact on their microenvironment.

The UV/Vis absorption band maximum λmax of trans-4,4′-nitrophenylaminoazobenzene, the thermal isomerization rate constant kiso of its cis-isomer, the fluorescence intensity ratio of monomer and excimer, and the fluorescence lifetime of the excimer, respectively, of 1,3-di(1-pyrenyl)propane were determined as probes for polarity, water content, and viscosity, respectively, in unilamellar vesicles of di-n-alkyl-dimethylammonium bromides and 1,2-acyl-sn-glycero-3-phosphocholines. The dependence on vesicle size, the solvent (water or HEPES buffer/NaCl solution, each with H2O or D2O), and the temperature (20–60 °C) was studied. Apparent Arrhenius activation energies and kinetic solvent isotope effects ( KSIE =k iso , H 2 O /k iso , D 2 O ) were derived. Size and stability of the vesicles prepared by extrusion were controlled by dynamic light scattering. The probe properties clearly indicate the reversibly decreasing size of didodecyldimethylammonium bromide vesicles with increasing temperature but are insensitive against vesicles size variation in most other cases. In the temperature range of the main phase transition of the bilayers, changes of the microenvironment of the probes, and their changing position in the bilayer, respectively, are reflected by characteristic changes of their properties. Buffer/NaCl solution causes vanishing influence of the lipid chain but remaining difference between cationic and zwitterionic headgroups probed by means of kiso.

The aggregation behavior of 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in the nonaqueous solvents formamide (FA) and 3-hydroxypropionitrile (HPN) has been studied. UV/Vis absorption maximum λmax and thermal cis → trans isomerization rate constant k iso of an azo dye, as well as fluorescence intensity ratios I M/I E of monomer and excimer, and the excimer lifetime τE of two dipyrenyl compounds as probe molecules have been determined. For comparison, aggregation of the amphiphile POPC molecules was followed “probe-free” by means of dynamic light scattering (DLS) measurements. Combining the results of probe molecule studies and DLS it turned out that the critical aggregation concentration of POPC in FA < 0.05mmol dm−3. At ≥ 0.2mmol dm−3, aggregates have hydrodynamic radii 30 < R h < 80nm and high microviscosity in their hydrocarbon interior. A vesicle-like structure of the aggregates can therefore be assumed. Aggregation behavior of POPC in HPN is much less pronounced, essentially small aggregates with radii of a few nanometer have been detected which include solvent molecules.

The interaction of the antimicrobial peptide dicynthaurin (ala) monomer with model membranes of zwitterionic and negatively charged lipids and mixtures thereof was studied by means of isothermal titration calorimetry (ITC), fluorescent leakage, and dynamic light scattering (DLS) measurements. For the ITC analysis, we have applied the surface partitioning equilibrium model which shows that the interaction is predominately driven by hydrophobic effects (Kb between 2 x 10(4) and 1 x 10(5) M(-1)). Under low salt conditions, the enhanced electrostatic interaction leads to larger peptide concentrations immediately above the vesicle surface, which initiates the insertion of the peptide into the bilayer more effectively. Fluorescent leakage measurements have shown a fast leakage of the fluorescent dye within seconds after peptide addition. The analysis of the leakage kinetics was performed in terms of an initial pore formation model (up to t = 1000 s) that takes the reversible surface aggregation of bound peptide monomers into account. From this analysis, a minimum aggregation number of n = 7 +/- 2 per pore is obtained.

This paper is focused on the thermodynamics and the structural investigation of the interaction of the antimicrobial peptide dicynthaurin monomer with model lipid membranes composed of mixtures of 1-palmitoyl-2-oleyl-glycerophosphocholine and -glycerophosphoglycerol. The thermodynamic binding parameters as obtained by isothermal titration calorimetry reveal strong binding toward the lipid model system dominated by large chemical binding constants which exceeds the electrostatic binding effects and thus suggests insertion of the amphipathic alpha-helical peptide into the hydrophobic membrane core. Circular dichroism study shows that the peptide exhibits trans-membrane alpha-helix secondary structure. Neutron diffraction measurements using partially deuterated sequences were successfully applied to determine the orientation of the peptide thus proving insertion into the hydrophobic membrane core. This insertion and the formation of higher order porelike aggregates is assumed to be the most relevant event in microbial membrane perturbation that in vivo finally leads to bacterial cell death on a fast time scale.

The adsorption of doubly lipidated full-length N-Ras protein on 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) monolayers was studied by lateral pressure analysis, grazing incidence X-ray diffraction (GIXD), and specular reflectivity (XR). N-Ras protein adsorbs to the DPPC monolayer (lateral pressure of 20 mN/m) from the subphase thereby increasing the lateral pressure in the monolayer by 4 mN/m. The protein insertion does not alter the tilt angle and structure of the lipid molecules at the air/water interface but influences the electron density profile of the monolayer. Further, electron density differences into the subphase were observed. The Fresnel normalized reflectivity could be reconstructed in the analysis using box models yielding electron density profiles of the DPPC monolayer in the absence and in the presence of N-Ras protein. The electron density profiles of the DPPC monolayer in the presence of Ras showed clear intensity variations in the headgroup/glycerol/upper chain region, the so-called interface region where previous bilayer studies had confirmed Ras binding.