Identification of alkyl substituted 2h-furo[2,3-c]pyran-2-ones as germination stimulants present in smoke

The butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), is a major compound in smoke responsible for promoting the seed germination of a wide range of plant species. We now report the structure of five alkyl substituted variants of 1 that are also present in smoke. The concentrations of these analogues, as well as that of 1, in a typical smoke-water solution have been determined using highperformance liquid chromatography (HPLC) purification followed by gas chromatography-mass spectrometry (GC-MS) analysis. The analogue, 3,5-dimethyl-2H-furo[2,3-c]pyran-2-one (3), was identified at levels that indicate that it is a contributor to the overall germination-promoting activity of crude smoke extracts

Synthesis of the seed germination stimulant 3-methyl-2H-furo[2,3-c]pyran-2-one

3-Methyl-2H-furo[2,3-c]pyran-2-one 1 was recently identified as the key agent in smoke, responsible for promoting the seed germination of a diverse range of fire-dependent and fire-independent plant species from around the world. The synthesis of this novel compound, obtained in three steps from pyromeconic acid, is described

A compound from smoke that promotes seed germination

Exposure of seeds to aerosol smoke or crude smoke extracts stimulates the germination of a number of fire-dependent and fire-independent plant species. We now report the identity of a germination-promoting compound present in plant- and cellulose-derived smoke. The structure of this compound, deduced from spectroscopic analysis and confirmed by synthesis, was shown to be that of the butenolide 3-methyl-2H-furo[2,3-c]pyran-2-one (1). Here we show that 1 promotes germination of a number of plant species at a level similar to that observed with plant-derived smoke water

Karrikins promote germination of physiologically dormant seeds of Chrysanthemoides monilifera ssp. monilifera (boneseed)

Summary: Physiological dormancy in weed species has significant implications for weed management, as viable seeds may persist in soil seedbanks for many years. The major stimulatory compound in smoke, karrikinolide (KAR1), promotes germination in a range of physiologically dormant weed species allowing targeted eradication methods to be employed. Control of Chrysanthemoides monilifera ssp. monilifera (boneseed), a Weed of National Significance in Australia, may benefit from adopting such an approach. In this study, we hypothesised that seeds of C. monilifera ssp. monilifera exhibit physiological dormancy, germinate more rapidly as dormancy is alleviated, show fluctuations in sensitivity to KAR1 and form a persistent soil seedbank. Seeds responded to 1 μM KAR1 (40-60% germination) even during months (i.e. March, April, July, August) when seeds were observed to be more deeply dormant (control germination: 7-20%). Seeds germinated readily over a range of cooler temperatures (i.e. 10, 15, 20, 20/10 and 25/15°C) and were responsive to KAR2 (~50% germination) as well. Eradication efforts for C. monilifera ssp. monilifera may benefit from use of karrikins to achieve synchronised germination from soil seedbanks, even at times of the year when C. monilifera ssp. monilifera seeds would be less likely to germinate, allowing more rapid depletion of the soil seedbank and targeted control of young plants. © 2013 European Weed Research Society

Structural analysis of a potent seed germination stimulant

A single-crystal x-ray crystallographic study of a seed germination stimulant isolated from plant-derived smoke was presented. The stimulant, 3-methyl-3H-furo[2,3-c]pyran-2-one, crystallized in monoclinic space group, with one molecule devoid of crystallographic symmetry comprising the asymmetric unit of the structure. The stimulant stimulates germination at levels as allow as 1 ppb in smoke-responsive species. The distances within the six-membered ring are symmetrical with the double bonds highly localized

Preparation of 2H-Furo[2,3-c]pyran-2-one Derivatives and Evaluation of Their Germination-Promoting Activity

The butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), has recently been identified as the germination stimulant present in smoke that promotes the germination of seeds from a wide range of plant species. In this paper, we describe the preparation of a number of analogues of 1 and compare their efficacy in promoting seed germination of three highly smoke-responsive plant species, Lactuca sativa L. cv. Grand Rapids (Asteraceae), Emmenanthe penduliflora Benth. (Hydrophyllaceae), and Solanum orbiculatum Poir. (Solanaceae). The results show that the methyl substituent at C-3 in 1 is important for germination-promoting activity while substitution at C-7 reduces activity. In contrast, bioactivity is mostly retained with analogues substituted at C-4 or C-5

Effects of a butenolide present in smoke on light-mediated germination of Australian Asteraceae

This study investigated the effects of 3-methyl-2H-furo[2,3-c]pyran-2-one, a germination active butenolide present in plant-derived smoke, gibberellic acid and smoke water on seeds of Australian Asteraceae exposed to different light regimes. Seeds of all species required light, with maximum germination occurring under white light, or light dominated by 640 nm. Compared to untreated seeds, butenolide increased germination of Angianthus tomentosus, Gnephosis tenuissima, Myriocephalus guerinae, Podolepis canescens and Rhodanthe citrina at suboptimal light wavelengths and in the dark to a level equal to, or greater than, smoke water. Germination of Erymophyllum glossanthus and Gnephosis acicularis was not promoted by butenolide or smoke water under any light regime. The action of gibberellic acid was compared to that of butenolide for three species (Angianthus tomentosus, Myriocephalus guerinae and Podolepis canescens), and both compounds were found to stimulate germination. This study provides evidence that butenolide can act in a similar fashion as gibberellic acid in promoting seed germination of light-sensitive seeds. The ecological significance of these findings is discussed

Inhibition of ruminal bacteria involved in lactic acid metabolism by extracts from Australian plants

Ethanolic extracts, essential oils and plant secondary compounds from selected Australian plants were tested in vitro for their potential to selectively inhibit bacteria associated with lactic acid production in ruminants. A combination of agar dilution and microbroth dilution assays were used to determine the minimum inhibitory concentration (MIC) of the plant extracts against a panel of ruminal bacteria. Ethanolic extract from Eremophila glabra inhibited lactate producers and all other rumen bacteria at 1.260. mg/ml, except for the ruminal lactate fermenter Megasphaera elsdenii (MIC 10. mg/ml). Extracts from Acacia decurrens, A. saligna, Kennedia eximia and K. prorepens inhibited ruminal lactate producer Lactobacillus spp. only (MIC from 5 to 10. mg/ml). The MIC of essential oils ranged from 0.003 to 0.020. mg/ml, but the inhibitory effect was not specific to lactate producers. E. glabra was identified as the plant with the most favourable effect and purified compounds from this plant were investigated for further analysis. Seven serrulatane diterpenes were isolated by chromatography and tested against the major ruminal lactate producer Streptococcus bovis and a lactate fermenter M. elsdenii in a microbroth dilution assay. All but one of these inhibited S. bovis, with the MIC ranging from 0.320 to 1.080. mg/ml, with only one compound also inhibiting M. elsdenii (MIC 1.080. mg/ml). Selective inhibition of lactate producing bacteria in the rumen by some Australian plant extracts and their secondary compounds was identified and may lead to further research into the application of bioactive plants in the management of lactic acidosis in ruminants

Rice cytochrome P450 MAX1 homologs catalyze distinct steps in strigolactone biosynthesis

Strigolactones (SLs) are a class of phytohormones and rhizosphere signaling compounds with high structural diversity. Three enzymes, carotenoid isomerase DWARF27 and carotenoid cleavage dioxygenases CCD7 and CCD8, were previously shown to convert all-trans-¿-carotene to carlactone (CL), the SL precursor. However, how CL is metabolized to SLs has remained elusive. Here, by reconstituting the SL biosynthetic pathway in Nicotiana benthamiana, we show that a rice homolog of Arabidopsis MORE AXILLARY GROWTH 1 (MAX1), encodes a cytochrome P450 CYP711 subfamily member that acts as a CL oxidase to stereoselectively convert CL into ent-2'-epi-5-deoxystrigol (B-C lactone ring formation), the presumed precursor of rice SLs. A protein encoded by a second rice MAX1 homolog then catalyzes the conversion of ent-2'-epi-5-deoxystrigol to orobanchol. We therefore report that two members of CYP711 enzymes can catalyze two distinct steps in SL biosynthesis, identifying the first enzymes involved in B-C ring closure and a subsequent structural diversification step of SLs

Rice cytochrome P450 MAX1 homologs catalyze distinct steps in strigolactone biosynthesis

Strigolactones (SLs) are a class of phytohormones and rhizosphere signaling compounds with high structural diversity. Three enzymes, carotenoid isomerase DWARF27 and carotenoid cleavage dioxygenases CCD7 and CCD8, were previously shown to convert all-trans-¿-carotene to carlactone (CL), the SL precursor. However, how CL is metabolized to SLs has remained elusive. Here, by reconstituting the SL biosynthetic pathway in Nicotiana benthamiana, we show that a rice homolog of Arabidopsis MORE AXILLARY GROWTH 1 (MAX1), encodes a cytochrome P450 CYP711 subfamily member that acts as a CL oxidase to stereoselectively convert CL into ent-2'-epi-5-deoxystrigol (B-C lactone ring formation), the presumed precursor of rice SLs. A protein encoded by a second rice MAX1 homolog then catalyzes the conversion of ent-2'-epi-5-deoxystrigol to orobanchol. We therefore report that two members of CYP711 enzymes can catalyze two distinct steps in SL biosynthesis, identifying the first enzymes involved in B-C ring closure and a subsequent structural diversification step of SLs