Phylogenetic Patterns of Swainsonine Presence in Morning Glories

Abstract

Endosymbionts play important roles in the life cycles of many macro-organisms. The indolizidine alkaloid swainsonine is produced by heritable fungi that occurs in diverse plant families, such as locoweeds (Fabaceae) and morning glories (Convolvulaceae) plus two species of Malvaceae. Swainsonine is known for its toxic effects on livestock following the ingestion of locoweeds and the potential for pharmaceutical applications. We sampled and tested herbarium seed samples (n = 983) from 244 morning glory species for the presence of swainsonine and built a phylogeny based on available internal transcribed spacer (ITS) sequences of the sampled species. We show that swainsonine occurs only in a single morning glory clade and host species are established on multiple continents. Our results further indicate that this symbiosis developed ∼5 mya and that swainsonine-positive species have larger seeds than their uninfected conspecifics.

Phylogenetic patterns of bioactive secondary metabolites produced by fungal endosymbionts in morning glories (Ipomoeeae, Convolvulaceae)

“…In grasses, Epichlo€ e infection has been found to reduce seed predation of symbiotic grasses by rodents (Uchitel et al, 2011) and birds (Madej & Clay, 1991). Herein, using data from Cook et al (2019), Beaulieu et al (2021), Quach et al (2022), and new IDT data, we find that species with secondary metabolites produced by an endosymbiont (EA, IDT, or SWN) have significantly larger seed size than those lacking the symbiosis (55.7 mg vs 32.7 mg, P = 0.0005, respectively). Interestingly, we found that within EA+ species, those that are also IDT+ have smaller, but nonsignificant, seed size than IDTÀ species (47.0 and 60.8 mg, respectively), suggesting that the production of additional types of alkaloids may involve additional costs to the host plant or is dependent on the endosymbiont species.…”

“…Notably, the SWN‐producing endosymbionts in morning glories are unrelated to those in locoweed legumes and to the Periglandula endosymbionts in other morning glories (Fig. 2; Quach et al ., 2022). Outside of these three families (Convolvulaceae, Fabaceae, and Poaceae), there is little evidence of widespread heritable fungal endosymbiosis in plants.…”

“…Within this single large clade there are several subclades; for example, there are two subclades specific to taxa that originate from Africa and Australia, respectively. Notably, while SWN is a single molecule, concentrations are greater among host taxa that originate from Africa (Quach et al ., 2022). Results from a different plant system (Braun et al ., 2003; Cook et al ., 2013) suggest that the genotype of the symbiont in SWN+ legumes is primarily responsible for determining SWN concentrations in the host.…”

Swainsonine Induces Liver Inflammation in Mice via Disturbance of Gut Microbiota and Bile Acid Metabolism

“…As alkaloid-synthesizing herbaceous legumes, locoweeds including toxic Oxytropis and Astraglus species are collectively responsible for the majority of livestock poisoning losses and seriously threaten animal husbandry on grasslands in China and the United States . Locoweeds have an impact not only on the livestock industry but also on ecology because locoweeds such as Oxytropis ochrocephala have evolved in a variety of adaptations, including drought, cold, and salt tolerance; as a result, they have replaced other plants and become dominant in the rangeland plant communities. , Swainsonine is the main toxic component of locoweed plants, and its chemical structure is shown in Figure S1, which can bring about livestock poisoning such as locoism marked by nervous system disorder. , In addition, the depression, behavior alteration, loss of weight, and even death of livestock may be caused by the ingestion of swainsonine-containing plants, and economic losses have been estimated to be tens of millions of dollars annually …”

“…4,5 In addition, the depression, behavior alteration, loss of weight, and even death of livestock may be caused by the ingestion of swainsonine-containing plants, and economic losses have been estimated to be tens of millions of dollars annually. 6 Liver inflammation is responsible for 32,000 deaths in the United States 7 and more than 1 million deaths every year worldwide. 8 Emerging evidence linking to liver diseases is related to intestinal disorders and hepatic metabolism, mainly via the gut−liver axis.…”