Butterfly eggs prime anti-herbivore defense in an annual but not perennial Arabidopsis species

While plant anti-herbivore defenses of the annual plant species Arabidopsis thaliana were shown to be primable by Pieris brassicae eggs, the primability of the phylogenetically closely related perennial Arabidopsis lyrata has not yet been investigated. Previous studies revealed that closely related wild Brassicaceae plant species, the annual Brassica nigra and the perennial Brassica oleracea, exhibit an egg-primable defense trait, even though they have different life spans. Here, we tested whether P. brassicae eggs prime anti-herbivore defenses of the perennial A. lyrata. We exposed A. lyrata to P. brassicae eggs and larval feeding and assessed their primability by i) determining the biomass of P. brassicae larvae after feeding on plants with and without prior P. brassicae egg deposition and ii) investigating the plant transcriptomic response after egg deposition and/or larval feeding. For comparison, these studies were also conducted with A. thaliana. Consistent with previous findings, A. thalianas response to prior P. brassicae egg deposition negatively affected conspecific larvae feeding upon A. thaliana. However, this was not observed in A. lyrata. Arabidopsis thaliana responded to P. brassicae eggs with strong transcriptional reprogramming, whereas A. lyrata responses to eggs were negligible. In response to larval feeding, A. lyrata exhibited a greater transcriptome change compared to A. thaliana. Among the strongly feeding-induced A. lyrata genes were those that are egg-primed in feeding-induced A. thaliana, i.e., CAX3, PR1, PR5 and PDF1.4. These results suggest that A. lyrata compensates for its lack of egg-mediated primability by a stronger response to larval feeding.