Abstract
Knowledge remains limited about how fungal pathogens that colonize living plant cells translocate effector proteins inside host cells to regulate cellular processes and neutralize defense responses. To cause the globally important rice blast disease, specialized invasive hyphae (IH) invade successive living rice (Oryza sativa) cells while enclosed in host-derived extrainvasive hyphal membrane. Using live-cell imaging, we identified a highly localized structure, the biotrophic interfacial complex (BIC), which accumulates fluorescently labeled effectors secreted by IH. In each newly entered rice cell, effectors were first secreted into BICs at the tips of the initially filamentous hyphae in the cell. These tip BICs were left behind beside the first-differentiated bulbous IH cells as the fungus continued to colonize the host cell. Fluorescence recovery after photobleaching experiments showed that the effector protein PWL2 (for prevents pathogenicity toward weeping lovegrass [Eragrostis curvula]) continued to accumulate in BICs after IH were growing elsewhere. PWL2 and BAS1 (for biotrophy-associated secreted protein 1), BIC-localized secreted proteins, were translocated into the rice cytoplasm. By contrast, BAS4, which uniformly outlines the IH, was not translocated into the host cytoplasm. Fluorescent PWL2 and BAS1 proteins that reached the rice cytoplasm moved into uninvaded neighbors, presumably preparing host cells before invasion. We report robust assays for elucidating the molecular mechanisms that underpin effector secretion into BICs, translocation to the rice cytoplasm, and cell-to-cell movement in rice.
Highlights
Intracellular animal and plant pathogens, including the rice blast fungus, spend at least the early stages in living host cells sequestered from the host cytoplasm by a membrane (O’Connell and Panstruga, 2006; Bhavsar et al, 2007; Kankanala et al, 2007)
All effector:fluorescent protein (FP) constructs were under control of the native promoters
Individual constructs were introduced into M. oryzae, and resulting transformants were analyzed for fluorescent protein secretion in rice sheath epidermal cells
Summary
Intracellular animal and plant pathogens, including the rice blast fungus, spend at least the early stages in living host cells sequestered from the host cytoplasm by a membrane (O’Connell and Panstruga, 2006; Bhavsar et al, 2007; Kankanala et al, 2007). For the eukaryotic pathogens, which are less-studied than prokaryotic pathogens, this raises the major question of how effectors are delivered across the plasma membrane to reach the host cytoplasm. We are addressing this question by studying rice blast disease, which is Hemibiotrophy in blast disease is characterized by successive biotrophic invasions of rice (Oryza sativa) cells by intracellular invasive hyphae (IH) that are surrounded by a plant-derived extrainvasive hyphal membrane (EIHM) (Kankanala et al, 2007). Intracellular invasion by the blast fungus differs from the invasion by rust and mildew fungi, which grow extracellularly and produce intracellular haustoria separated from host cytoplasm by extrahaustorial membrane (Mendgen and Hahn, 2002; O’Connell and Panstruga, 2006)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
