Endophyte-derived alkaloids relieve the growth-defence trade-off of plants

A central paradigm in plant biology is that a trade-off exists between growth and defence. This paradigm is based on recurrent observations that increased defence responses are often associated with compromised plant growth, providing obvious limits to increasing the productivity of crop plants that also must resist pests and pathogens.Using mRNA-seq, we evaluated growth and defence responses to herbivores of plants with Epichloe festucae var. lolii able (wild type (wt) and idtA removed) and unable (idtM removed) to produce bioactive alkaloids subjected to an exogenous application of GA hormone. Lolium perenne plants without (nil) and with Epichloe festucae var. lolii variants were treated with GA3 followed by a challenge with Rhopalosiphum padi aphids.Using gene-edited fungal endophytes, we demonstrated that the Epichloe festucae var. lolii-derived production of alkaloids was the mechanism that relieve the growth-defence trade-off of plants relatively independent from the host plant immunity.