CRC TRR 175/2: Challenged (by) parasites—Plastid-mediated acclimation kinetics of a plant-plant-pathosystem (SP A08)

Plastids are a plant cells’ center to sense, coordinate, and respond to abiotic challenges, while also being a hub for plant defense against biotic stressors. Dual biotic:abiotic combinations of stressors are perceived by plants as a new state of environmental challenge, but the nature of plastid integration into plant responses to dual challenges remain unexplored. This project aims to identify novel players of plastid-mediated acclimation by studying the kinetics of Arabidopsis under dual-challenge conditions. At the same time, we will elucidate the role of plastid-mediated environmental responses in the pathogenic plant Phelipanche ramosa (Orobanchaceae, “broomrape”), which serves as the biotic stressor. We will i) determine and compare the acclimation kinetics of parasitized Arabidopsis when exposed to high light, heat, or cold by phenotyping the semi-in vitro grown Arabidopsis:P.ramosa pathosystem, ii) analyze molecular responses of both pathosystem partners under dual-challenge conditions by RNA sequencing, RNA modification-sensitive ELISA, and ROS assays, and iii) evaluate the fitness of P.ramosa-challenged Arabidopsis mutants with functional deficiencies in key modulators and integrators of plastid acclimation. These data will be analyzed using time course-dependent coexpression networks, focusing primarily on plastid-centered pathways. A subsequent synergistic analysis will fuse Arabidopsis’ (and P.ramosa’s) differential responses in single- versus dual-challenge situations on the transcript (RNAseq) and post-transcriptional level (ELISA) with the physiological reaction (ROS production). The novelty of this biotic:abiotic study lies in its design with a biotic stressor that is a plant itself: P. ramosa lives completely of the resources of its host Arabidopsis. The pathogenic plant cannot photosynthesize, which allows studying conserved acclimation responses, with the potential to unveil responses independent from canonical key functions of the chloroplast in fully autotrophic plants. Therefore, our study of plastid-based response kinetics of the Arabidopsis:P.ramosa pathosystem promises to identify novel, very basal modulations in molecular acclimation processes.