Chang Hyun Khang

University of Georgia | UGA · Department of Plant Biology

To cause the devastating rice blast disease, the hemibiotrophic fungus Magnaporthe oryzae produces invasive hyphae (IH) that are enclosed in a plant-derived interfacial membrane, known as the extra-invasive hyphal membrane (EIHM), in living rice cells. Little is known about when the EIHM is disrupted and how the disruption contributes to blast dise...

Structured Illumination Microscopy enables live imaging with sub-diffraction resolution. Unfortunately, optical aberrations can lead to loss of resolution and artifacts in Structured Illumination Microscopy rendering the technique unusable in samples thicker than a single cell. Here we report on the combination of Adaptive Optics and Structured Ill...

The blast fungus, Magnaporthe oryzae , causes severe destruction to rice and other crops worldwide. As the fungus infects rice, it develops unique cellular structures, such as an appressorium and a narrow penetration peg, to permit successful invasion of host rice cells. Fundamental knowledge about these cellular structures and how organelles, such...

During plant infection, fungi secrete effector proteins in coordination with distinct infection stages. Thus, the success of plant infection is determined by precise control of effector gene expression. We analysed the PWL2 effector gene of the rice blast fungus Magnaporthe oryzae to understand how effector genes are activated specifically during t...

Pathogens utilize multiple types of effectors to modulate plant immunity. Although many apoplastic and cytoplasmic effectors have been reported, nuclear effectors have not been well characterized in fungal pathogens. Here, we characterize two nuclear effectors of the rice blast pathogen Magnaporthe oryzae. Both nuclear effectors are secreted via th...

The arrangement of the nuclear envelope in the rice blast fungus, Magnaporthe oryzae, was previously undetermined. Here, we identified two conserved components of the nuclear envelope, a core nucleoporin, Nup84, and an inner nuclear membrane protein, Src1. Live-cell super-resolution structured illumination microscopy revealed that Nup84-tdTomato an...

Unlike most characterized bacterial plant pathogens, the broad-host-range plant pathogen Pantoea ananatis lacks both the virulence-associated type III and type II secretion systems. In the absence of these typical pathogenicity factors, P. ananatis induces necrotic symptoms and extensive cell death in onion tissue dependent on the HiVir proposed se...

Structured Illumination Microscopy enables live imaging with resolutions of ~120 nm. Unfortunately, optical aberrations can lead to loss of resolution and artifacts in Structured Illumination Microscopy rendering the technique unusable in samples thicker than a single cell. Here we report on the combination of Adaptive Optics and Structured Illumin...

Onion ( Allium. cepa L), garlic ( A. sativum L.), and other members of the Allium genus produce volatile antimicrobial thiosulfinates upon cellular damage. Allicin has been known since the 1950s as the primary antimicrobial thiosulfinate compound and odorant produced by garlic. However, the roles of endogenous thiosulfinate production in host-bacte...

To cause rice blast disease, Magnaporthe oryzae must properly organize microtubules and position nuclei during colonization of host cells. Live cell confocal imaging of fluorescently-tagged microtubules and nuclei of M. oryzae invasive hyphae reveals that microtubules form a cage-like arrangement around nuclei during interphase and that the mitotic...

During biotrophy, filamentous pathogens such as the rice blast fungus Magnaporthe oryzae deliver effector proteins into live host cells to facilitate colonization. We describe three complementary assays for visualizing M. oryzae effector translocation into the rice cytoplasm and cell-to-cell movement during infection. Our assays make use of live-ce...

We describe a fluorescence imaging method to visualize the dynamics of the central vacuole in rice cells during invasion by the blast fungus Magnaporthe oryzae. This method utilizes the combination of confocal microscopy, rice sheath cells (optically transparent), fluorescently tagged M. oryzae (red fluorescence), and fluorescein diacetate staining...

Magnaporthe oryzae is a filamentous fungus, which causes significant destruction to cereal crops worldwide. To infect plant cells, the fungus develops specialised constricted structures such as the penetration peg and the invasive hyphal peg. Live-cell imaging of M. oryzae during plant infection reveals that nuclear migration occurs during intermed...

The rice blast fungus Pyricularia oryzae (syn. Magnaporthe oryzae, Magnaporthe grisea), a member of the order Magnaporthales in the class Sordariomycetes, is an important plant pathogen and a model species for studying pathogen infection and plant-fungal interaction. In this study, we generated genome sequence data from five additional Magnaporthal...

The hemibiotrophic fungus Magnaporthe oryzae produces invasive hyphae enclosed in a plant-derived interfacial membrane, known as the extra-invasive hyphal membrane (EIHM), in living rice cells. Little is known about when the EIHM is disrupted and how the disruption contributes to blast disease. Here we show that EIHM disruption correlates with the...

Background To cause an economically important blast disease on rice, the filamentous fungus Magnaporthe oryzae forms a specialized infection structure, called an appressorium, to penetrate host cells. Once inside host cells, the fungus produces a filamentous primary hypha that differentiates into multicellular bulbous invasive hyphae (IH), which ar...

To investigate the mitotic dynamics of an appressorium, we used live-cell confocal imaging of a fluorescence-based mitotic reporter strain of Magnaporthe oryzae. We present evidence that the M. oryzae appressorium remains viable and mitotically active well after host penetration. These results suggest the potential roles of the appressorium during...

To investigate the mitotic dynamics of an appressorium, we used time-lapse confocal imaging of a fluorescence-based mitotic reporter strain of Magnaporthe oryzae . We present evidence that: (i) appressoria remain viable and mitotically active after host penetration, (ii) appressorial mitosis, like invasive hyphal mitosis, is semi-closed, (iii) sist...

Background To cause an economically important blast disease on rice, the filamentous fungus Magnaporthe oryzae forms a specialized infection structure, called an appressorium, to penetrate host cells. Once inside host cells, the fungus produces a filamentous primary hypha that differentiates into multicellular bulbous invasive hyphae (IH), which ar...

To study nuclear dynamics of _Magnaporthe oryzae,_ we developed a novel mitotic reporter strain with GFP-NLS (localized in nuclei during interphase but in the cytoplasm during mitosis) and H1-tdTomato (localized in nuclei throughout the cell cycle). Time-lapse confocal microscopy of the reporter strain during host cell invasion provided several new...

Annual ryegrass (Lolium multiflorum Lam.) is a highly nutritive, fast-growing, C3 cool-season annual forage. Blast or gray leaf spot is a fungal disease of ryegrass caused by Magnaporthe orygae (anamporph Pyricularia oryzae). The disease kills seedlings as well as adult plants. Blast-resistant annual ryegrass cultivars are not available at present....

Plant cell death plays important roles during plant-pathogen interactions. To study pathogen-induced cell death, there is a need for cytological tools that allow determining not only host cell viability, but also cellular events leading to cell death with visualization of pathogen development. Here we describe a live cell imaging method to provide...

of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Relative abundance of transcripts from the 57 conidiation-specific TF genes during conidiation and/or in conidia. (PDF)

Conditions used to extract RNA samples for gene expression analyses. (PDF)

Primers used for quantitative real-time PCR. (PDF)

Conidiation at four different time points. (A) Pictures of fungal culture on cellulose nitrate membrane filter laid with on V8-Juice agar medium from 0 h to 24 h. (B) Numbers of conidia (per plate) at the indicated time. (C) Diagram illustrating conidiation process based on microscopic observation. Three genes involved at different stages of conidi...

T-DNA insertion sites in eight mutants defective in conidiation-specific TF genes and resulting phenotypes. Phenotypes of these mutants are derived from Magnaporthe oryzae T-DNA insertion mutant library (http://atmt.snu.ac.kr). (PDF)

List of TF genes up-regulated under developmental conditions. (PDF)

Because most efforts to understand the molecular mechanisms underpinning fungal pathogenicity have focused on studying the function and role of individual genes, relatively little is known about how transcriptional machineries globally regulate and coordinate the expression of a large group of genes involved in pathogenesis. Using quantitative real...

Although the functions of a few effector proteins produced by bacterial and oomycete plant pathogens have been elucidated in recent years, information for the vast majority of pathogen effectors is still lacking, particularly for those of plant-pathogenic fungi. Here, we show that the avirulence effector AvrPiz-t from the rice blast fungus Magnapor...

To cause rice blast disease, the fungus Magnaporthe oryzae produces biotrophic invasive hyphae that secrete effectors at the host-pathogen interface. Effectors facilitate disease development, but some (avirulence effectors) also trigger the host's resistance gene-mediated hypersensitive response and block disease. The number of cloned M. oryzae avi...

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...

Biotrophic invasive hyphae (IH) of the blast fungus Magnaporthe oryzae secrete effectors to alter host defenses and cellular processes as they successively invade living rice (Oryza sativa) cells. However, few blast effectors have been identified. Indeed, understanding fungal and rice genes contributing to biotrophic invasion has been difficult bec...

In planta secretion of fungal pathogen proteins, including effectors destined for the plant cell cytoplasm, is critical for disease progression. However, little is known about the endoplasmic reticulum (ER) secretion mechanisms used by these pathogens. To determine if normal ER function is crucial for fungal pathogenicity, Magnaporthe oryzae genes...

To cause rice blast disease, Magnaporthe oryzae sequentially invades living plant cells using intracellular invasive hyphae (IH) that grow from cell to cell. However, detailed cellular and molecular mechanisms underlying biotrophic invasion are poorly understood. We used live-cell microscopy and fluorescent molecular probes to visualize biotrophic...

The hemibiotrophic fungus Magnaporthe oryzae causes the devastating rice blast disease using specialized intracellular invasive hyphae (IH) that successively invade living plant cells. IH differentiate from thin filamentous primary hyphae that form immediately af ter the appressorial penetration peg breaches the exterior plant surface. At this poin...

The avirulence (AVR) gene AVR-Pita in Magnaporthe oryzae prevents the fungus from infecting rice cultivars containing the resistance gene Pi-ta. A survey of isolates of the M. grisea species complex from diverse hosts showed that AVR-Pita is a member of a gene family, which led us to rename it to AVR-Pita1. Avirulence function, distribution, and ge...

Rapid translation of genome sequences into meaningful biological information hinges on the integration of multiple experimental and informatics methods into a cohesive platform. Despite the explosion in the number of genome sequences available, such a platform does not exist for filamentous fungi. Here we present the development and application of...

ABSTRACT Plant pathogen culture collections are essential resources in our fight against plant disease and for connecting discoveries of the present with established knowledge of the past. However, available infrastructure in support of culture collections is in serious need of improvement, and we continually face the risk of losing many of these c...

A better understanding of fungal biology will facilitate judicious use of beneficial fungi and will also advance our efforts to control pathogenic fungi. Molecular studies of fungal biology have been greatly aided by transformation-mediated mutagenesis techniques. Transformation via nonhomologous integration of plasmid DNA bearing a selectable mark...

The rice blast fungus, Magnaporthe grisea, requires formation of an appressorium, a dome-shaped and highly melanized infection structure, to infect its host. cAMP was identified as an important second messenger in signaling systems for appressorium formation in this fungus. To understand further the role of cAMP in infection-related morphogenesis,...

Rapid progress in fungal genome sequencing presents many new opportunities for functional genomic analysis of fungal biology through the systematic mutagenesis of the genes identified through sequencing. However, the lack of efficient tools for targeted gene replacement is a limiting factor for fungal functional genomics, as it often necessitates t...

Sequence analysis of a 13-kb telomeric region in O-137, a rice pathogenic isolate of Magnaporthe grisea, uncovered a novel gene, designated TLH1 (telomere-linked helicase 1). The TLH1 gene is a member of a gene family, and the sequences flanking this gene family have also been amplified. Genetic mapping showed that most members of the TLH gene fami...