Inducible defense provided by Neotyphodium to Lolium arundinacea and lolium pratense: an ecological and molecular approach

Plants have evolved a range of responses to herbivory ranging from tolerance to both inducible and constitutive chemical defenses. Previous research has shown lolines produced by Neotyphodium coenophialum are inducible by host damage. In this paper, we examined whether this inducibility can also be caused by damage from an invertebrate herbivore and whether this phenomenon also occurs in N. uncinatum. We also investigated whether changes in gene expression for lolC, a gene in the loline biosynthesis pathway, accompanies changes in defense response. For N. coenophialum, both mechanical and herbivore damage had a negative effect on subsequent aphid herbivores. For N. uncinatum, damage did not cause an increase in defense, although there was an increase in endophyte-free hosts. Relative expression of lolC varied significantly over time, and between damage types for N. uncinatum with herbivore damaged plants having a lower relative lolC -1 expression. Keywords: Neotyphodium, gene expression, inducible defense, loline, lolC

The genome and genes of Epichloe festucae

The ascomycete Epichloë festucae is a model endophyte that 1) switches between mutualistic and antagonistic states, 2) is seed transmissible, 3) has a sexual state amenable to genetic analysis, and 4) is rich in bioprotective alkaloids. This fungus grows systemically and intercellularly throughout the life of its host plant. On each reproductive tiller the fungus either infects benignly and transmits clonally in seeds, or produces its sexual state (stroma) and chokes inflorescence development. The E. festucae genome was estimated at 29 Mb in six chromosomes. The genome sequence was assembled from cloned insert end reads (4.2 x coverage) and preassembled pyrosequencing reads (454-sequencing: 20 x raw, 1.7 x assembled), giving 3967 supercontigs, of which 1004 were larger than 2 kb and covered 92% of the genome. Gene prediction with FGENESH identified ~10,000 putative genes. We also sequenced 25,000 ESTs from each of two normalised libraries — one of choked inflorescences, the other of benignly infected inflorescences — yielding 5077 E. festucae unigenes, annotated by BLAST and InterPro. Sequence data and annotations are stored in a database for visualisation and inspection with the GBrowse browser. The genomic sequences can be queried by BLAST at http://www.genome.ou.edu/blast/ ef_blastall.html. Keywords: bioinformatics, DNA sequence, Epichloë festucae, expressed sequence tags, Festucae pratensis, fungal genomics, Lolium pratense

Endophyte-mediated multitrophic interactions in Lolium pratense

The nature of plant-endophyte relationships may be affected by the addition of interacting species. Firstly, we show how the root hemiparasitic plant (Rhinanthus serotinus) can steal defending mycotoxins produced by the symbiotic endophytic fungus (Neotyphodium uncinatum) living within their shared host grass (Lolium pratense). The uptake of defensive mycotoxins from the endophyte infected host increases resistance of the hemiparasitic plant to the aphid (Aulacorthum solani). Endophyte infection increased performance of the hemiparasite but reduced the growth of the host grass, changing the mutualistic endophytic fungus to parasitic. Secondly, we present the interactions among endophyte, host plant, aphid herbivore (Rhopalosiphum padi) and aphid transmitted grass virus (BYDV). Endophyte infection lowered the frequency of BYDV in L. pratense. The reproduction of R. padi aphids was decreased on endophyte-infected plants compared to uninfected. With these results we would like to emphasise the importance of experiments with several community members to shed light on the complexity of endophyte-mediated community interactions. Keywords: Lolium pratense, Neotyphodium uncinatum, Rhinanthus serotinus, BYDV, aphid, multitrophic interactions

Endophytic fungus decreases plant virus infections in meadow ryegrass ( Lolium pratense )

We studied the effects of fungal endophyte infection of meadow ryegrass ( Lolium pratense = Festuca pratensis ) on the frequency of the barley yellow dwarf virus (BYDV). The virus is transferred by aphids, which may be deterred by endophyte-origin alkaloids within the plant. In our experiment, we released viruliferous aphid vectors on endophyte-infected and endophyte-free plants in a common garden. The number of aphids and the percentage of BYDV infections were lower in endophyte-infected plants compared to endophyte-free plants, indicating that endophyte infection may protect meadow ryegrass from BYDV infections.