Acropetal and basipetal cardenolide transport in Erysimum cheiranthoides (wormseed wallflower)

Plant specialized metabolites are often subject to within-plant transport and have tissue-specific distribution patterns. Among plants in the Brassicaceae, the genus Erysimum is unique in producing not only glucosinolates but also cardenolides as defense against insect herbivory. Ten cardenolides were detected with varying abundance in different tissues of Erysimum cheiranthoides (wormseed wallflower). As is predicted by the optimal defense theory, cardenolides were most abundant in young leaves and reproductive tissues. The lowest concentrations were observed in senescing leaves and roots. Crosses between wildtype E. cheiranthoides and a mutant line with an altered cardenolide profile showed that the seed cardenolide phenotype is determined entirely by the maternal genotype. Prior to the development of the first true leaves, seedling cotyledons also had the maternal cardenolide profile. Hypocotyl grafting experiments showed that the root cardenolide profile is determined entirely by the aboveground plant genotype. In further grafting experiments, there was no evidence of cardenolide transport into the leaves, but a mixed cardenolide profile was observed in the stems and inflorescences of plants that had been grafted at vegetative and flowering growth stages, respectively. Together, these results indicate that E. cheiranthoides leaves are a site of cardenolide biosynthesis and therefore also the plant tissue that is most likely to be expressing the relevant biosynthetic genes.

Less Is More: A Mutation in the Chemical Defense Pathway of Erysimum cheiranthoides (Brassicaceae) Reduces Total Cardenolide Abundance but Increases Resistance to Insect Herbivores

Many plants produce structurally related defensive metabolites with the same target sites in insect herbivores. Two possible drivers of this chemical diversity are: (i) interacting effects of structurally related compounds increase resistance against individual herbivores, and (ii) variants of the same chemical structures differentially affect diverse herbivore species or feeding guilds. Erysimum cheiranthoides L (Brassicaceae; wormseed wallflower) produces abundant and diverse cardenolide toxins, which are derived from digitoxigenin, cannogenol, and strophanthidin, all of which inhibit Na+/K+-ATPases in animal cells. Here we describe an E. cheiranthoides mutant with 66% lower cardenolide content, resulting from greatly decreased cannogenol- and strophanthidin-derived cardenolides, partially compensated for by increases in digitoxigenin-derived cardenolides. This compositional change created a more even cardenolide distribution, decreased the average cardenolide polarity, but did not impact glucosinolates, a different class of chemical defenses. Growth of generalist herbivores from two feeding guilds, Myzus persicae Sulzer (Hemiptera: Aphididae; green peach aphid) and Trichoplusia ni Hübner (Lepidoptera: Noctuidae; cabbage looper), was decreased on the mutant line compared to wildtype. Both herbivores accumulated cardenolides in proportion to plant content, with T. ni accumulating higher total concentrations than M. persicae. Helveticoside, an abundant cardenolide in E. cheiranthoides, was absent in M. persicae, suggesting that this compound is not present in the phloem. Our results support the hypothesis that cardenolide diversity protects plants against different herbivores, with digitoxigenin-derived compounds providing better protection against insects like M. persicae and T. ni, whereas cannogenol and strophanthidin provide better protection against other herbivores of E. cheiranthoides.FundingThis research was funded by US National Science Foundation awards 1907491 to AAA and 1645256 to GJ and AAA, Swiss National Science Foundation grant PZ00P3-161472 to TZ, and a Triad Foundation grant to GJ.

Rzadkie gatunki flory kalcyfilnej w zbiorowiskach segetalnych na terenie województwa lubelskiego

Celem badań była dokumentacja stanowisk rzadkich gatunków kalcyfilnej flory segetalnej na terenie woj. lubelskiego. W pracy przedstawiono wyniki badań terenowych prowadzonych w latach 2005–2010 na polach zlokalizowanych na glebach rędzinowych. Każdą agrocenozę, w której stwierdzono występowanie gatunku uznanego za rzadki i zagrożony wyginięciem, traktowano jako odrębne stanowisko. Z grupy rzadkich taksonów kalcyfilnych w zbiorowiskach segetalnych na terenie woj. lubelskiego stwierdzono występowanie: Adonis aestivalis, Anagallis foemina, Anchusa arvensis, Anthemis tinctoria, Bromus secalinus, Camelina microcarpa, Cerinthe minor, Chaenorrhinum minus, Conringia orientalis, Consolida regalis, Erysimum cheiranthoides, Euphorbia exigua, Fumaria vaillantii, Lathyrus tuberosus, Melampyrum arvense, Melandrium noctiflorum, Muscari comosum, Neslia paniculata, Odontites verna, Salvia verticillata, Sherardia arvensis, Silene dichotoma, Stachys annua, Thlaspi perfoliatum, Valerianella dentata, Valerianella rimosa, Veronica agrestis, Veronica polita. Gatunki te zarejestrowano w 54 miejscowościach.