Occurrence of quinoiizidine alkaloids in legumes

Legumes are able to fix atmospheric nitrogen via symbiotic Rhizobia in root nodules. Thus, nitrogen is easily available for secondary metabolism, and it is probably not surprising that nitrogen-containing SM (alkaloids, nonprotein amino acids [NPAAs], cyanogens, protease inhibitors, lectins) are a common theme in i 10 36

legumes.

Quinolizidine alkaloids figure as the most prominent group of alkaloids in legumes, present in members of "genistoid alliance s.l." of the subfamily Papilionoideae including the tribes Genisteae, Crotalarieae, Podalyrieae/Liparieae, Thermopsideae, Euchresteae, Brongniartiaeae, and Sophoreae.15,48 Also ,dipiperidine alkaloids of the ammodendrine type, which also derive from lysine as a precursor, exhibit a comparable distribution pattern.

As can be seen from Figure 9.1, most taxa of the genistoid alliance accumulate QAs. An obvious exception are members of the large tribe Crotalarieae, that either sequester PAs and/or NPAAs. In Lotonis some taxa produce QAs, others PAs. Since Crotalaria and Lotonis derive from ancestors which definitely produced QAs but not PAs, we suggest that the genes encoding biosynthetic enzymes of QA formation must still be present. It is unlikely that corresponding genes have been lost. More likely the QA genes have been turned off in Crotalaria and partially in Lotononis. The formation of PAs instead appears to be a new acquisition for chemical defense, which probably evolved independently. In a few other taxonomic groups which cluster within QA accumulating genera, QAs are hardly detectable or levels are very low, such as in Ulex, Calicotome, or Spartocytisus. These taxa have extensive spines in common that apparently have substituted chemical defense; in this case, the presence or absence of QAs is clearly a trait reflecting rather different ecological strategies than taxonomic relationships.

Occurrence of Quinolizidine alkaloids

Rafnia amplexicaulis Crotalaria macrocarpa Crotalaria pumila Crotalaria natalica

Anagyris foetida

Virgilia divaricat CLiycplaorpiiaa sgpeleninsdtenoisd

Podalyria calyptr<

Dalbergia granadillo Tipuana tipu Arachis hypogaea Amicia zygomeris_

Colutea ■iabilrssc Sutherlandia frute Caragana arborescens •alimodendron halodendron

Trigonella crética Ononis spinosa Trifolium pratense

Campylotropis , macrocarpa

Eutaxia obovata Pultenaea daphnoi Daviesia cordata Burtonia scabra Goodia lotifolia

Enterolobium cvclocaroum

Tamaríndus índica

Figure 9.1

Adenocarpus complicatus Chamaespartium sagittale Genista florida Cytisophyllum sessilifoliu Teline monspessulana Argyrocytisus battandieri Stauracanthus genistoides

Calicotome villosa Chamaecytisus proliferus Cytisus scoparius Spartocytisus supranubius Laburnum anagyroides Lupinus albescens Lupinus albus

Genisteae

Rafnia amplexicaulis Crotalaria macrocarpa Crotalaria pumila Crotalaria natalica

Crotalarieae

Anagyris foetida

Thermopsideae

Sophoreae II

Virgilia divaricat CLiycplaorpiiaa sgpeleninsdtenoisd

Podalyria calyptr<

Podalyrieae

Brongniartieae

Dalbergia granadillo Tipuana tipu Arachis hypogaea Amicia zygomeris_

Dalbergieae/ Aeschynomeneae

Astragalus Gueldensta Oxytropis cam

Hedysareae

Astragalus Gueldensta Oxytropis cam

Colutea ■iabilrssc Sutherlandia frute Caragana arborescens •alimodendron halodendron

Galegeae

Vicieae

Trigonella crética Ononis spinosa Trifolium pratense

Ornithopus compressu Dorycnium hirsutum Lotus corniculatus Tetragonolobus purpureus

•Hspsu^ verscsuatus

Coronilla emerus

Trifolieae

Loteae (Coronilleae)

pseudaca

Campylotropis , macrocarpa

Robinieae

Desmodieae

•ardenbergia comptonia Kennedia coccinea Mucuna macrocarpa Amphicarpaea bracteata Neonotonia wightii Pueraria lobata

Pachyrrhizus erosus Calopogonium caeruleum Glycine max Dolichos glabra Phaseolus vulgaris Sphenostylis stenocarpa Macrotyloma africanum Vigna unguiculata jy~'~igia strobi

Phaseoleae

Millettieae

1 purpureum

Eutaxia obovata Pultenaea daphnoi Daviesia cordata Burtonia scabra Goodia lotifolia btusangelicum

Mirbelieae

Bossiaeeae

Ormosia formosana Myroxylon balsamum Sophora secundiflora Castanospermum australe Cladrastis sinensis Styphnolobium japonicum

Sophoreae I

Acacieae

Enterolobium cvclocaroum

Ingeae

Neptunia plena Leucaena leucocephala Parkia roxburghii -■■-'■ -istachys glomerat ithera miirosperi

Mimoseae/ Parkieae

Senna pletirocarpa

Parkinsorneiagi aacu "~~""1lÍÍussiÍií

Caesalpinieae/ Cassieae

Cercideae

Tamaríndus índica brachypetala

Detarieae

" Polygala chamaebiuxius

Outgroup

Figure 9.1

Distribution of alkaloids in legumes. Branches leading to taxa that accumulate QA are printed in bold.

dentatum

Within the genistoid alliance, all taxa (except the few examples mentioned before) produce alkaloids of the sparteine/lupanine type, at least as minor alkaloids. a-Pyridone alkaloids, such as anagyrine and cytosine, are apparently already present in the more ancestral tribes of the Papilionoideae, but also in the more advanced Cytisus/Genista complex of the Genisteae, suggesting that already the ancestor of genistoids must have possessed the biosynthetic capacity to produce these alkaloids. This suggests also that the pathway leading to a-pyridone alkaloids is present at the genomic level in the early stages of legume phylogeny, but not expressed in most advanced taxa.59

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