An amino acid ester of menthol elicits defense responses in plants.

KEY MESSAGE: Valine menthyl ester (ment-Val) acts as a plant defense potentiator for several crop species including soybean. Terpenoids, including menthol, exhibit potent abilities as plant defense potentiators in agriculture and horticulture. In the current study, we developed new terpene derivatives that consisted of menthol and various amino acids and that were expected to act as powerful plant defense potentiators. We used 6 amino acids possessing low-reactive sidechains to synthesize an array of amino acid ester of menthol (ment-aa) compounds. Transcript levels of two defense genes (pathogenesis-related protein 1 [PR1] and trypsin inhibitor [TI]) were evaluated in leaves of soybean plants 24 h after application of aquatic solution of menthol or menthol-aa, and revealed that the valine menthyl ester (ment-Val) alone elevated the transcript level of defense genes, and it did so only at the low dose of 1 µM, not at higher or lower doses tested. Moreover, it appeared that histone acetylation was involved in this effect. Application of ment-Val enabled soybean plants to sustain the increased transcript levels in their leaves for up to 3 days. Moreover, when ment-Val was additionally applied at day 4, at which time the transcript level had declined to the basal level, the transcript level was re-elevated, indicating the possibility that ment-Val could be repeatedly used to sustain pest control. Ment-Val was found to be chemically stable and effective for defense of several crop species. Collectively, these data show that terpenoid conjugates are useful for pest control instead of or in addition to pesticides.

Soy and Arabidopsis receptor-like kinases respond to polysaccharide signals from Spodoptera species and mediate herbivore resistance.

Plants respond to herbivory by perceiving herbivore danger signal(s) (HDS(s)), including "elicitors", that are present in herbivores' oral secretions (OS) and act to induce defense responses. However, little is known about HDS-specific molecules and intracellular signaling. Here we explored soybean receptor-like kinases (RLKs) as candidates that might mediate HDS-associated RLKs' (HAKs') actions in leaves in response to OS extracted from larvae of a generalist herbivore, Spodoptera litura. Fractionation of OS yielded Frα, which consisted of polysaccharides. The GmHAKs composed of their respective homomultimers scarcely interacted with Frα. Moreover, Arabidopsis HAK1 homomultimers interacted with cytoplasmic signaling molecule PBL27, resulting in herbivory resistance, in an ethylene-dependent manner. Altogether, our findings suggest that HAKs are herbivore-specific RLKs mediating HDS-transmitting, intracellular signaling through interaction with PBL27 and the subsequent ethylene signaling for plant defense responses in host plants.

Synthesis of an O-sulfo Lewis(X) analog as glycolipid antigen.

The title compound containing dihydroceramide as a ligand for CD1d was accomplished using the mannosyl, glucosaminyl, and fucosyl donors, and a sphinganine analogue, as suitable building blocks. The 2-O-unprotected mannosyl donor was coupled effectively with the sphinganine analog to afford the mannnosyl sphinganine derivative. The coupling of the glucosaminyl donor with the mannnosyl sphinganine acceptor required triflic acid as a promoter and the promoter change to silver triflate led to the undesired glycal production. The reduction of azide group using Zn powder was the key process, in which the amount of acetic acid was restricted to avoid the benzoyl migration and N-trichloroacetyl deprotection. The trisaccharide glycolipid was sulfonated at the 3-position of fucose moiety.

Solvent-induced anomeric diastereoselectivity switching using a single glycosyl donor.

Highly diastereoselective glycosylation reactions have been developed; however, not all glycosylation reactions are diastereoselective and these reactions have probably not been reported. For some fucosylation reactions, unusually low or abnormally opposite selectivities have been demonstrated. In the present study, the fucosylation reaction of long-chain hydrocarbon alcohols, ethyl 9-hydroxynonanoate and decanol using a series of the 2-O-benzyl-protected fucopyranosyl donors were investigated. The resulting products demonstrated the solvent-induced diastereoselectivity switching using diethyl ether (Et(2)O) or dichloromethane (CH(2)Cl(2)). Practical α-selectivities were observed using ether solvents. In contrast, practical ß-selectivities were observed using CH(2)Cl(2). The anomeric diastereoselectivity switching was similarly observed in the alcohol galactosylation reaction. The larger spin-lattice relaxation time constant (T(1)) actually indicated that molecular motion of ethyl 9-hydroxynonanoate was more vigorous in Et(2)O than in CH(2)Cl(2), suggesting its dissociation in Et(2)O and association in CH(2)Cl(2). The bulkiness of the associated alcohols is most likely responsible for the observed diastereoselectivity.

Atomic force microscopy studies of ganglioside GM1alpha in dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine mixed monolayers and hybrid bilayers.

The membrane states of the alpha-series ganglioside GM1alpha in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) mixed monolayers and hybrid bilayers were investigated using atomic force microscopy (AFM). The AFM image for the GM1alpha/DOPC/DPPC ternary monolayers showed the formation of GM1alpha-raft in the DOPC matrix. As increase of the surface pressure, GM1alpha are condensed in DPPC-rich domains; long and slender GM1alpha-rafts are separated from the DPPC-rich domains into the DOPC matrix. The GM1alpha/DOPC/DPPC ternary monolayers were deposited on mica coated with the first layer (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine: DPPE) using the Langmuir-Schaeffer technique. The AFM image for the hybrid bilayers showed that same molecules were heterogeneously concentrated according to increase of the surface pressure to form GM1alpha-raft, DPPC-rich domain and DOPC matrix, being in agreement with the observation on the monolayer experiment. The found phenomenon implies that a binding of lectin to GM1alpha causes the increase of the surface pressure, the localization of GM1alpha and the succeeding formation of the raft as a first step of a specific signal transduction.

Synthesis of alpha-series ganglioside GM1alpha containing C20-sphingosine.

A synthesis of alpha-series ganglioside GM1alpha (III(6)Neu5AcGgOse4Cer) containing C20-sphingosine(d20:1) is described. Glycosylation of 2-(trimethylsilyl)ethyl 2,3,6-tri-O-benzyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside with the glucosamine donor ethyl 3-O-acetyl-2-deoxy-4,6-O-[(4-methoxyphenyl)methylene]-2-phthalimido-1-thio-beta-D-glucopyranoside furnished a beta-(1-->4)-linked trisaccharide. Reductive cleavage of the p-methoxybenzylidene group followed by intramolecular inversion of its triflate afforded the desired trisaccharide, which was transformed into a trisaccharide acceptor via removal of the phthaloyl and O-acetyl groups followed by N-acetylation. A tetrasaccharide acceptor was obtained by glycosylation of the trisaccharide acceptor with dodecyl 2,3,4,6-tetra-O-benzoyl-1-thio-beta-D-galactopyranoside, followed by removal of the p-methoxybenzyl group. Coupling of the tetrasaccharide acceptor with ethyl (methyl 4,7,8,9-tetra-O-acetyl-3,5-dideoxy-1-thio-5-trichloroacetamido-D-glycero-D-galacto-2-nonulopyranosid)onate and subsequent radical reduction gave the desired GM1alpha saccharide derivative, which was coupled with (2S,3R,4E)-2-azido-3-O-benzoyl-4-eicosene-1,3-diol after conversion into the imidate.