Browsing by Author "Herlihy, John H."
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- The Impact of Iron Deficiency on Plant-Oomycete InteractionsHerlihy, John H. (Virginia Tech, 2020-04-08)Plants are sessile organisms adapted to cope with dynamic changes in their environment. Abiotic stresses, such as heat, drought, or nutrient deficiency must be overcome simultaneously with biotic threats such as pathogens and herbivores. Oomycete pathogens represent a significant threat to global food production and natural ecosystems. Novel modes of oomycete disease control could increase crop yield and reduce pesticide application. Overlaps between the plant response to iron deficiency and pathogens have been documented, but the impact of simultaneous imposition of both stresses on the plant have not been studied. Additionally, nothing is known about the impact of iron deficiency on oomycete infection, or mechanisms of oomycete iron uptake. We adapted a hydroponic system to simultaneously impose iron deficiency and monitor pathogen infection. The oomycete pathogens Hyaloperonospora arabidopsidis, and Phytophthora capsici grew less well on iron-deficient Arabidopsis thaliana, at least in part because of observed activation of immunity due to iron stress. We screened A. thaliana T-DNA insertion mutants defective in iron metabolism and transport and identified potential mechanisms of H. arabidopsidis iron acquisition. We conducted RNA sequencing to understand how A. thaliana responds to iron deficiency and root infection of P. capsici. 323 genes were differentially upregulated in iron-starved plants over three days, irrespective of pathogen infection, representing a core iron deficiency response. This group of core genes included the primary A. thaliana iron uptake pathway and genes for coumarin biosynthesis. Salicylic acid responsive genes were observed in both treatments consistent with this defense hormone's previously identified role in iron deficiency. Genes related to glucosinolate production – shown to be important in defense against P. capsici – were down regulated during infection, potentially due to the activity of virulence effectors. Our work demonstrates crosstalk between the iron deficiency response and plant immunity, and that iron acquisition remains important to the plant even after pathogen invasion. These new insights provide a first step in developing novel resistance strategies to control oomycetes in agronomically important crops.
- Iron homeostasis and plant immune responses: Recent insights and translational implicationsHerlihy, John H.; Long, Terri A.; McDowell, John M. (2020-09-25)Iron metabolism and the plant immune system are both critical for plant vigor in natural ecosystems and for reliable agricultural productivity. Mechanistic studies of plant iron home-ostasis and plant immunity have traditionally been carried out in isolation from each other; however, our growing understanding of both processes has uncovered significant connections. For example, iron plays a critical role in the generation of reactive oxygen intermediates during immunity and has been recently implicated as a critical factor for immune-initiated cell death via ferroptosis. Moreover, plant iron stress triggers immune activation, suggesting that sensing of iron depletion is a mechanism by which plants recognize a pathogen threat. The iron deficiency response engages hormone signaling sectors that are also utilized for plant immune signaling, providing a probable explanation for iron-immunity cross-talk. Finally, interference with iron acquisition by pathogens might be a critical component of the immune response. Efforts to address the global burden of iron deficiency-related anemia have focused on classical breeding and transgenic approaches to develop crops biofortified for iron content. However, our improved mechanistic understanding of plant iron metabolism suggests that such alterations could promote or impede plant immunity, depending on the nature of the alteration and the virulence strategy of the pathogen. Effects of iron biofortification on disease resistance should be evaluated while developing plants for iron biofortification.