Developmentally regulated activation of defense allows for rapid inhibition of infection in age-related resistance to Ph
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RESEARCH ARTICLE
Open Access
Developmentally regulated activation of defense allows for rapid inhibition of infection in age-related resistance to Phytophthora capsici in cucumber fruit Ben N. Mansfeld1, Marivi Colle1, Chunqiu Zhang1,2, Ying-Chen Lin1 and Rebecca Grumet1*
Abstract Background: Age-related resistance (ARR) is a developmentally regulated phenomenon conferring resistance to pathogens or pests. Although ARR has been observed in several host-pathogen systems, the underlying mechanisms are largely uncharacterized. In cucumber, rapidly growing fruit are highly susceptible to Phytophthora capsici but become resistant as they complete exponential growth. We previously demonstrated that ARR is associated with the fruit peel and identified gene expression and metabolomic changes potentially functioning as preformed defenses. Results: Here, we compare the response to infection in fruit at resistant and susceptible ages using microscopy, quantitative bioassays, and weighted gene co-expression analyses. We observed strong transcriptional changes unique to resistant aged fruit 2–4 h post inoculation (hpi). Microscopy and bioassays confirmed this early response, with evidence of pathogen death and infection failure as early as 4 hpi and cessation of pathogen growth by 8–10 hpi. Expression analyses identified candidate genes involved in conferring the rapid response including those encoding transcription factors, hormone signaling pathways, and defenses such as reactive oxygen species metabolism and phenylpropanoid biosynthesis. Conclusion: The early pathogen death and rapid defense response in resistant-aged fruit provide insight into potential mechanisms for ARR, implicating both pre-formed biochemical defenses and developmentally regulated capacity for pathogen recognition as key factors shaping age-related resistance. Keywords: Age-related resistance, Ontogenic resistance, Cucumber, Phytophthora capsici, Plant defense, Transcriptome, Co-expression networks
Background Ontogenic, developmental, or age-related resistance (ARR), wherein plants or plant organs transition from susceptibility to resistance as a result of developmental changes [1–3], has been described in several different plant-pathogen systems and in crops such as pepper, grape, rice, wheat, and several * Correspondence: [email protected] 1 Graduate Program in Plant Breeding, Genetics and Biotechnology and Department of Horticulture, Michigan State University, 1066 Bogue St, East Lansing, MI 48824, USA Full list of author information is available at the end of the article
cucurbit crops [4–8]. While providing protection in agricultural systems and potentially playing an important role in the evolution and optimization of host resistance [9], the molecular mechanisms controlling these resistances are not well understood. Evidence from various systems suggests possible physical, chemical, or physiological changes that may result from age-dependent, non-pathogen specific investment in defense such as cell wall modifications, production of antimicrobial
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