Asexual spore biology,
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The asexual spores of P. infestans play very important roles in the disease cycle. The spores serve as the primary inoculum for epidemics caused by P. infestans. Many generations of the asexual cycle occur per season, spreading disease through a field. Chemical or environmental conditions that suppress asexual sporulation can control late blight and other diseases by breaking this cycle. Consequently, identifying factors that control sporulation, plus ways to interrupt the normal cell cycle, will lead to new strategies for crop protection.

Sporulation occurs toward the end of the life cycle. Older hyphae produce asexual spores upon a specialized aerial hypha called the sporangiophore. Usually, sporangiophores are branched and bear multiple spores. The spores contain multiple nuclei, which can partition into individual zoospores upon germination (see below). Unlike the spores (conidia) of true fungi, Phytophthora spores do not desiccate and remain metabolically active.

Soon after they germinate, the sporangia are capable of forming specialized structures for penetrating a host plant.

hyphae forming aerial sporangiophores.

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Asexual sporangia

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A few of the questions that we are trying to answer in our studies of asexual sporulation include:

1. What genes and proteins are required for forming spores?
2. What is the metabolic/cellular trigger of sporulation?
3. How is the pattern of transcription altered in hyphae to "turn on" the genes expressed during sporulation?
4. What sequence elements within promoters are required for spore-specific patterns of expression?
5. Which components of spores are used for germination?