Evaluation of endophyte toxin production and its interaction with transgenic perennial ryegrass (Lolium perenne L.) with altered expression of fructosyltransferases

Abstract

Alkaloid concentration of perennial ryegrass herbage is affected by endophyte strain and host plant genotype. However, previous studies suggest that associations between host and endophyte also depends on environmental conditions, especially those affecting nutrient reserves and that water-soluble carbohydrate (WSC) concentration of perennial ryegrass plants may influence grass-endophyte associations. In this study a single transgenic event, with altered expression of fructosyltransferase genes to produce high WSC and biomass, has been crossed into a range of cultivar backgrounds with varying Epichloë endophyte strains. The effect of the association between the transgenic trait and alkaloid production was assessed and compared with transgene free control populations. In the vast-majority of comparisons there was no significant difference between alkaloid concentrations of transgenic and non-transgenic plants within the same cultivar and endophyte backgrounds. There was no significant difference between GOI+ (gene of interest positive) and GOI- (gene of interest negative) populations in Janthritrem response. Peramine concentration was not different between GOI+ and GOI- for 10 of the 12 endophytes-cultivar combinations. Cultivar Trojan infected with NEA6 and Alto with SE (standard endophyte) exhibited higher peramine and lolitrem B (only for Alto SE) concentration, in the control GOI- compared with GOI+. Similarly, cultivar Trojan infected with NEA6 and Alto with NEA3 presented higher ergovaline concentration in GOI-. Differences in alkaloid concentration may be attributable to an indirect effect in the modulation of fungal biomass. These results conclude that the presence of this transgenic insertion, does not alter the risk (toxicity) of the endophyte-grass associations. Endophyte-host interactions are complex and further research into associations with high WSC plant should be performed in a case by case basis.

Epichloë fungal endophyte interactions in perennial ryegrass (Lolium perenne L.) modified to accumulate foliar lipids for increased energy density

“…Similar reductions in endophyte-derived alkaloid concentrations, to those observed in endophyte infected DGAT + CO, have been described in previous experiments which measured endophyte-derived alkaloid concentration and mycelial biomass in perennial ryegrass cultivars with elevated levels of water-soluble carbohydrate (WSC) developed with traditional breeding techniques or from populations using recombinant technologies [ 38 , 39 ]. Using two perennial ryegrass cultivars differing in carbohydrate content infected with three Epichloë strains (AR1, AR37, and a common-toxic strain) Rasmussen et al .…”

“…In a similar set of experiments, Giraldo et al . [ 38 ] examined the interaction of secondary metabolite production in plants expressing a chimeric fusion of sucrose: sucrose 1-fructosyltransferase and fructosyltransferase genes (SST-FFT), to produce high levels of WSC. Clones of a T 0 founder plant from a single transformation event were used to generate seed derived from a range of cultivars infected with various Epichloë strains in an experiment designed to determine if insertion, or expression, of SST-FFT altered the toxicity of the endophyte-grass association.…”

“…A significant difference in alkaloid concentration was detected between SST-FFT and the null-segregant progeny in 5 of 28 combinations investigated. Peramine was reduced by 62% and 61% in two of the associations with cultivar ‘Trojan’ infected with strain NEA6 and cultivar ‘Alto’ infected with a common-toxic strain, respectively, however, no statistically significant differences in epoxyjanthitrem concentrations were identified for any of the cultivar combinations [ 38 ]. Nonetheless, stability of the SST-FFT phenotype (WSC and biomass) following introduction of the endophyte into this germplasm was not reported.…”

“…[ 45 ], may be influential in maintaining endophyte-derived alkaloid levels within Epichloë -perennial ryegrass associations with DGAT + CO. For instance, Giraldo et al . [ 38 ] proposed that differences in endophyte-derived alkaloids detected in the high WSC transgenic plants might not be related to alkaloid biosynthesis but may result from a phenomenon known as the “dilution effect” first described by Lane and Christensen [ 46 ]. This can be most succinctly described as environmental factors stimulating plant growth in excess of endophyte growth.…”

The impacts of space mutation and host genotype on endophyte role in host perennial ryegrass stress tolerance

“…Perennial ryegrass (Lolium perenne) is a globally important forage and turf grass species due to its desirable agronomic performance in temperate climates. Ryegrass has remarkable characteristics that makes it a dominant species, of which the most outstanding are high herbage yield and quality, favorable palatability and high grazing persistence (Yamada et al 2005;Giraldo et al 2018). Extensive studies have con rmed that Epichloë festucae var.…”