Homer Christina M, Voorhies Mark, Walcott Keith, Ochoa Elena, Sil Anita
Division of Infectious Diseases, University of California San Francisco, San Francisco, California, United States of America.
Department of Microbiology and Immunology, University of California San Francisco, San Francisco, California, United States of America.
PLoS Biol. 2025 Apr 15;23(4):e3003066. doi: 10.1371/journal.pbio.3003066. eCollection 2025 Apr.
Coccidioides spp. are highly understudied but significant dimorphic fungal pathogens that can infect both immunocompetent and immunocompromised people. In the environment, they grow as multicellular filaments (hyphae) that produce vegetative spores called arthroconidia. Upon inhalation by mammals, arthroconidia undergo a process called spherulation. They enlarge and undergo numerous nuclear divisions to form a spherical structure, and then internally segment until the spherule is filled with multiple cells called endospores. Mature spherules rupture and release endospores, each of which can form another spherule, in a process thought to facilitate dissemination. Spherulation is unique to Coccidioides, and its molecular determinants remain largely unknown. Here, we report the first high-density transcriptomic analyses of Coccidioides development, defining morphology-dependent transcripts and those whose expression is regulated by RYP1, a major regulator required for spherulation and virulence. Of approximately 9,000 predicted transcripts, we discovered 273 transcripts with consistent spherule-associated expression, 82 of which are RYP1-dependent, a set likely to be critical for Coccidioides virulence. ChIP-Seq revealed two distinct regulons of Ryp1: one shared between hyphae and spherules and the other unique to spherules. Spherulation regulation was elaborate, with the majority of 227 predicted transcription factors in Coccidioides displaying spherule-enriched expression. We identified provocative targets, including 20 transcripts whose expression is endospore-enriched and 14 putative secreted effectors whose expression is spherule-enriched, of which six are secreted proteases. To highlight the utility of these data, we selected a cluster of Ryp1-dependent, arthroconidia-associated transcripts and found that they play a role in arthroconidia cell wall biology, demonstrating the power of this resource in illuminating Coccidioides biology and virulence.
球孢子菌属是研究程度极低但重要的双相真菌病原体，可感染免疫功能正常和免疫功能低下的人群。在环境中，它们以多细胞细丝（菌丝）的形式生长，产生称为关节孢子的营养孢子。被哺乳动物吸入后，关节孢子会经历一个称为球形体形成的过程。它们会增大并经历多次核分裂以形成球形结构，然后在内部进行分割，直到球形体充满称为内生孢子的多个细胞。成熟的球形体破裂并释放内生孢子，每个内生孢子都可以形成另一个球形体，这一过程被认为有助于传播。球形体形成是球孢子菌属所特有的，其分子决定因素在很大程度上仍然未知。在此，我们报告了球孢子菌属发育的首次高密度转录组分析，确定了形态依赖性转录本以及那些表达受RYP1调控的转录本，RYP1是球形体形成和毒力所需的主要调节因子。在大约9000个预测转录本中，我们发现了273个与球形体相关且表达一致的转录本，其中82个依赖于RYP1，这一组转录本可能对球孢子菌属的毒力至关重要。染色质免疫沉淀测序（ChIP-Seq）揭示了Ryp1的两个不同调控子：一个在菌丝和球形体之间共享，另一个是球形体所特有的。球形体形成的调控很复杂，球孢子菌属中预测的227个转录因子中的大多数都表现出球形体富集表达。我们确定了一些有吸引力的靶点，包括20个表达在内生孢子中富集的转录本和14个表达在球形体中富集的假定分泌效应子，其中6个是分泌蛋白酶。为了突出这些数据的实用性，我们选择了一组依赖于Ryp1、与关节孢子相关的转录本，发现它们在关节孢子细胞壁生物学中发挥作用，证明了该资源在阐明球孢子菌属生物学和毒力方面的作用。
