Abstract
In Arabidopsis (Arabidopsis thaliana), a hypersensitive-like response (HR-like response) is triggered underneath the eggs of the large white butterfly Pieris brassicae (P. brassicae), and this response is dependent on salicylic acid (SA) accumulation and signaling. Previous reports indicate that the clade I L-type LECTIN RECEPTOR KINASE-I.8 (LecRK-I.8) is involved in early steps of egg recognition. A genome-wide association study was used to better characterize the genetic structure of the HR-like response and discover loci that contribute to this response. We report here the identification of LecRK-I.1, a close homolog of LecRK-I.8, and show that two main haplotypes that explain part of the variation in HR-like response segregate among natural Arabidopsis accessions. Besides, signatures of balancing selection at this locus suggest that it may be ecologically important. Disruption of LecRK-I.1 results in decreased HR-like response and SA signaling, indicating that this protein is important for the observed responses. Furthermore, we provide evidence that LecRK-I.1 functions in the same signaling pathway as LecRK-I.8. Altogether, our results show that the response to eggs of P. brassicae is controlled by multiple LecRKs.
Highlights
Eggs of herbivorous insects deposited on plant leaves are immobile and inert structures, they represent a future threat when hatching larvae start to feed
We found that high linkage disequilibrium (LD) with other surrounding markers was only observed for SNPs found in the gene sequence of like receptor kinases (LecRKs)-I.1 (Fig. 2B), suggesting that this gene may be causal for the differences in hypersensitive response (HR)-like responses elicited by egg extract (EE)
We describe here the identification of LecRK-I.1 as a component of the EE-triggered signaling pathway in Arabidopsis that affects the induction of HR-like responses during this interaction
Summary
Eggs of herbivorous insects deposited on plant leaves are immobile and inert structures, they represent a future threat when hatching larvae start to feed. A release of volatiles or changes in leaf surface chemistry attract natural egg predators (Hilker and Meiners, 2006; Fatouros et al, 2012) While these defense mechanisms impact egg mortality individually, some studies found that the co-induction of both direct and indirect defense strategies synergistically impact egg survival (Fatouros et al, 2014). Introgression of egg-killing traits in cultivated varieties has been reported in O. sativa (Yamasaki et al, 2003; Yang et al, 2014). It is still a mostly unexploited strategy due to a lack of mechanistic understanding of these responses at molecular and cellular levels (Reymond, 2013; Fatouros et al, 2016)
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