Obligate Lifestyle Research Articles

Elucidating the obligate nature and biological capacity of an invasive fungal corn pathogen.

Tar spot is a devasting corn disease caused by the obligate fungal pathogen Phyllachora maydis. Since its initial identification in the United States in 2015, P. maydis has become an increasing threat to corn production. Despite this, P. maydis has remained largely understudied at the molecular level due to difficulties surrounding its obligate lifestyle. Here, we generated a significantly improved P. maydis nuclear and mitochondrial genome using a combination of long- and short-read technologies and also provide the first transcriptomic analysis of primary tar spot lesions. Our results show that P. maydis is deficient in inorganic nitrogen utilization, is likely heterothallic, and encodes for significantly more protein coding genes, including secreted enzymes and effectors, than previous determined. Furthermore, our expression analysis suggests that following primary tar spot lesion formation, P. maydis might reroute carbon flux away from DNA replication and cell division pathways and towards pathways previously implicated in having significant roles in pathogenicity, such as autophagy and secretion. Together, our results identified several highly expressed unique secreted factors that likely contribute to host recognition and subsequent infection, greatly increasing our knowledge of the biological capacity of P. maydis, which have much broader implications for mitigating tar spot of corn.

Wheat Curl Mite: A New Source of the Eriophyoid Mite in Wheat Fields Identified

Wheat curl mites (WCMs; Aceria tosichella) are an important global pest of cultivated wheat. Their feeding activities on epidermal cells of wheat leaves result in characteristic leaf curl symptoms that prevent the unfurling of affected leaves and impair the proper emergence of heads from the boot stage. The most significant economic impact of WCM infestation, however, is their ability to vector and transmit four important viruses of wheat, specifically, wheat streak mosaic virus, Triticum mosaic virus, High Plains wheat mosaic emaravirus, and brome streak mosaic virus. Being wingless, WCMs are almost completely dependent on air currents for their dispersal. In addition, because of their obligate lifestyle, wheat field infestations are thought to originate from sources such as volunteer wheat. Corn and other cultivated and noncultivated Poaceae hosts are also known to act as green bridges between successive wheat crops. Consequently, management practices mostly target these off-season host plants but also the use of resistant varieties and other cultural control methods. Here we report the discovery of seed-borne WCM eggs, a previously unknown method of their dispersal, as a possible source of new infestations in wheat fields. This discovery expands our understanding of the biology of WCMs, with potential implications for the development of more holistic and effective management strategies for this economic pest and virus vector. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

PLoS Genetics Issue Image | Vol. 7(2) February 2011

Leaf-cutter ants are widespread neotropical herbivores that farm a fungus for food using leaves. This obligate ant-fungus symbiosis forms the foundation of their complex societies and their colonies can contain millions of workers ranging in size from small fungus tenders to large soldiers. In this issue of PLoS Genetics, Suen et al. report the genome sequence of the leaf-cutter ant Atta cephalotes. Genome comparisons with other social and non-social insects reveal features of their obligate lifestyle. These include loss of genes involved in nutrient acquisition and amino acid biosynthesis, suggesting a role in helping to stabilize this ant-fungus mutualism over its ancient coevolutionary history. Image Credit: Alex Wild.