Transcriptional programs controlling sporulation in Phytophthora respond to nutrition, humidity, and cryptochrome-mediated light signals
- 1Department of Microbiology and Plant Pathology, University of California, Riverside, United States of America.
Abstract
Many filamentous pathogens employ environmental signals to regulate sporulation, maximizing the likelihood that their spores survive to colonize a new host. In the oomycete Phytophthora, little is known of the transcriptional program that underlies sporangia formation and how it is influenced by environmental inputs such as light, humidity, and nutrients. By studying time courses of the potato blight pathogen P. infestans on artificial media and tomato leaves, we identified over 4000 genes up-regulated during sporulation. These are associated with signal transduction, cell structure, vesicle trafficking, metabolism, flagellar assembly, and other processes required for sporangium formation and germination. Most of their mRNAs remain abundant in mature sporangia. Media manipulation and metabolomic studies indicated that sporulation is triggered by nitrogen limitation, with asparagine and possibly other amino acids playing the main role. Light, which delays sporulation in P. infestans, apparently influences a later regulatory step since while many sporulation-induced transcripts oscillate with a day/night cycle, others are light-neutral. Both blue and red wavelengths result in the light response, which is likely mediated by a cryptochrome. One cryptochrome was shown to be required for sporulation based on gene silencing experiments. Humidity appears to regulate a late checkpoint, since while spore development requires high humidity, low humidity has only limited effects on sporulation-associated transcription. Comparative studies with P. capsici, which unlike P. infestans requires light for sporulation, yielded evidence of substantial rewiring of the transcriptional program between the species. The contrasting light responses within the genus correlate with whether species are primarily leaf colonizers such as P. infestans or root colonizers such as P. capsici. Author summary: Many disease-causing microbes use environmental cues to control the production of spores, which are used to spread the pathogen to new hosts. To better understand sporulation, we tracked changes in gene activity during spore production by Phytophthora infestans, a major pathogen of potato and tomato. We identified several thousand genes that become active during sporulation to build spores and prepare them for germination. We found that a shortage of amino acids triggers spore formation, and that the pathways that control sporulation respond to light and humidity. Species that primarily infect leaves, such as P. infestans, mostly sporulate at night, which minimizes damage to their spores from daytime light and heat. In contrast, light stimulates spore production in species of Phytophthora that colonize underground plant tissues, promoting sporulation on tissues emerging from soil where dispersal is more likely. These contrasting responses to light were associated with species-specific changes in the transcriptional program that controls sporulation. Our findings identify biological pathways that could be targeted by new chemicals to help reduce crop losses caused by disease.
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BibTeX
@article{vu2026transcriptional,
title = {{Transcriptional programs controlling sporulation in Phytophthora respond to nutrition, humidity, and cryptochrome-mediated light signals}},
author = {Andrea L Vu and Timothy A Harris and Howard S Judelson},
journal = {PLOS Pathogens},
year = {2026},
month = oct,
doi = {10.1371/journal.ppat.1014705},
url = {https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014705},
note = {CC BY},
}
RIS
TY - JOUR
TI - Transcriptional programs controlling sporulation in Phytophthora respond to nutrition, humidity, and cryptochrome-mediated light signals
AU - Andrea L Vu
AU - Timothy A Harris
AU - Howard S Judelson
PY - 2026
DA - 2026/10/12
JO - PLOS Pathogens
DO - 10.1371/journal.ppat.1014705
UR - https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014705
AB - Many filamentous pathogens employ environmental signals to regulate sporulation, maximizing the likelihood that their spores survive to colonize a new host. In the oomycete Phytophthora, little is known of the transcriptional program that underlies sporangia formation and how it is influenced by environmental inputs such as light, humidity, and nutrients. By studying time courses of the potato blight pathogen P. infestans on artificial media and tomato leaves, we identified over 4000 genes up-regulated during sporulation. These are associated with signal transduction, cell structure, vesicle trafficking, metabolism, flagellar assembly, and other processes required for sporangium formation and germination. Most of their mRNAs remain abundant in mature sporangia. Media manipulation and metabolomic studies indicated that sporulation is triggered by nitrogen limitation, with asparagine and possibly other amino acids playing the main role. Light, which delays sporulation in P. infestans, apparently influences a later regulatory step since while many sporulation-induced transcripts oscillate with a day/night cycle, others are light-neutral. Both blue and red wavelengths result in the light response, which is likely mediated by a cryptochrome. One cryptochrome was shown to be required for sporulation based on gene silencing experiments. Humidity appears to regulate a late checkpoint, since while spore development requires high humidity, low humidity has only limited effects on sporulation-associated transcription. Comparative studies with P. capsici, which unlike P. infestans requires light for sporulation, yielded evidence of substantial rewiring of the transcriptional program between the species. The contrasting light responses within the genus correlate with whether species are primarily leaf colonizers such as P. infestans or root colonizers such as P. capsici. Author summary: Many disease-causing microbes use environmental cues to control the production of spores, which are used to spread the pathogen to new hosts. To better understand sporulation, we tracked changes in gene activity during spore production by Phytophthora infestans, a major pathogen of potato and tomato. We identified several thousand genes that become active during sporulation to build spores and prepare them for germination. We found that a shortage of amino acids triggers spore formation, and that the pathways that control sporulation respond to light and humidity. Species that primarily infect leaves, such as P. infestans, mostly sporulate at night, which minimizes damage to their spores from daytime light and heat. In contrast, light stimulates spore production in species of Phytophthora that colonize underground plant tissues, promoting sporulation on tissues emerging from soil where dispersal is more likely. These contrasting responses to light were associated with species-specific changes in the transcriptional program that controls sporulation. Our findings identify biological pathways that could be targeted by new chemicals to help reduce crop losses caused by disease.
SN - 1553-7374
SN - 1553-7366
ER -