Eukaryotic cells use microtubule-based intracellular transport for the delivery of many subcellular cargos, including organelles. The canonical view of organelle transport is that organelles directly recruit molecular motors via cargo-specific adaptors. In contrast with this view, we show here that peroxisomes move by hitchhiking on early endosomes, an organelle that directly recruits the transport machinery. Using the filamentous fungus Aspergillus nidulans we found that hitchhiking is mediated by a novel endosome-associated linker protein, PxdA. PxdA is required for normal distribution and long-range movement of peroxisomes, but not early endosomes or nuclei. Using simultaneous time-lapse imaging, we find that early endosome-associated PxdA localizes to the leading edge of moving peroxisomes. We identify a coiled-coil region within PxdA that is necessary and sufficient for early endosome localization and peroxisome distribution and motility. These results present a new mechanism of microtubule-based organelle transport in which peroxisomes hitchhike on early endosomes and identify PxdA as the novel linker protein required for this coupling.
Functions of protein SUMOylation remain incompletely understood in different cell types. The budding yeast SUMOylation machinery interacts with LIS1, a protein critical for dynein activation, but dynein-pathway components were not identified as SUMO-targets in the filamentous fungus
Rice blast is caused by the fungus Magnaporthe grisea, which elaborates specialized infection cells called appressoria to penetrate the tough outer cuticle of the rice plant Oryza sativa. We found that the formation of an appressorium required, sequentially, the completion of mitosis, nuclear migration, and death of the conidium (fungal spore) from which the infection originated. Genetic intervention during mitosis prevented both appressorium development and conidium death. Impairment of autophagy, by the targeted mutation of the MgATG8 gene, arrested conidial cell death but rendered the fungus nonpathogenic. Thus, the initiation of rice blast requires autophagic cell death of the conidium.
Periodic conductivity trends are placed in the scope of lithium-ion batteries, where increases in the ionic radii of salt components affect the conductivity of a poly(ethyleneoxide)-based polymer electrolyte. Numerous electrolytes containing varying concentrations and types of metal salts are prepared and evaluated in either one or two laboratory sessions, requiring cooperation between all students in the classroom. The experiment is suitable for either high school students with a general chemistry background or undergraduate students in introductory general chemistry courses, as a number of fundamental topics can be discussed with this simple, inexpensive, and real-world-oriented project.
Rice blast disease, caused by the fungus Magnaporthe oryzae , destroys enough rice each year to feed 60 million people, and is a major threat to global food security. To establish disease, M. oryzae forms a specialized infection structure called an appressorium, which it uses to physically break into rice leaves. Essential for this process is the timely assembly of a septin ring structure at the base of the appressorium. Septins are a conserved family of GTP‐binding proteins, forming hetero‐oligomeric rods and filaments that are organized into higher‐order structures at the cell cortex. The M. oryzae septin ring scaffolds the formation of a donut‐shaped filamentous actin network, needed for the emergence of a polarized penetration structure from the base of the appressorium. Importantly, relatively little is understood about how higher‐order septin structures form in the right place and at the right time in appressoria to drive infection. We are using a proximity‐dependent proteomics to identify novel proteins involved in septin organization, and are functionally characterizing these using reverse genetics, and cell biological approach. We genetically tagged the septin protein Cdc11/Sep5 with TurboID, and identified a host of putatively proximal and interacting proteins. Here, we validate a number of these, and investigate their broader role in fungal biology. The outcomes of this research will provide fundamental new insight into the cellular control of septin organization in a global cereal killer.
Fungal hyphal growth and branching are essential traits that allow fungi to spread and proliferate in many environments. This sustained growth is essential for a myriad of applications in health, agriculture, and industry. However, comparisons between different fungi are difficult in the absence of standardized metrics. Here, we used a microfluidic device featuring four different maze patterns to compare the growth velocity and branching frequency of fourteen filamentous fungi. These measurements result from the collective work of several labs in the form of a competition named the “Fungus Olympics.” The competing fungi included five ascomycete species (ten strains total), two basidiomycete species, and two zygomycete species. We found that growth velocity within a straight channel varied from 1 to 4 μm/min. We also found that the time to complete mazes when fungal hyphae branched or turned at various angles did not correlate with linear growth velocity. We discovered that fungi in our study used one of two distinct strategies to traverse mazes: high-frequency branching in which all possible paths were explored, and low-frequency branching in which only one or two paths were explored. While the high-frequency branching helped fungi escape mazes with sharp turns faster, the low-frequency turning had a significant advantage in mazes with shallower turns. Future work will more systematically examine these trends.
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