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Highly abundant and stage-specific mRNAs in the obligate pathogen Bremia lactucae

H S Judelson1, R W Michelmore

  • 1Department of Vegetable Crops, University of California, Davis 95616.

Molecular Plant-Microbe Interactions : MPMI
|July 1, 1990
PubMed

Insights

Lettuce downy mildew (Bremia lactucae) spores contain abundant, specific mRNAs crucial for germination and growth. Researchers identified five key mRNA classes, aiding understanding of pathogen development and potential transformation strategies.

Area of Science:

  • Plant Pathology
  • Molecular Biology
  • Biochemistry

Background:

  • Bremia lactucae, the lettuce downy mildew pathogen, exhibits unique molecular characteristics during its life cycle.
  • Germinating spores of B. lactucae are known to contain abundant and diverse mRNA species.

Purpose of the Study:

  • To identify and characterize abundant mRNA transcripts in germinating Bremia lactucae spores.
  • To investigate the expression patterns of these transcripts during spore germination and in planta growth.
  • To explore the potential of highly expressed genes for developing transformation vectors for B. lactucae.

Main Methods:

  • Isolation and characterization of cDNA clones from poly(A)+ RNA of germinating B. lactucae spores.
  • Analysis of mRNA expression using Northern hybridization during germination and in planta.
  • Gene copy number determination through hybridization analysis.
  • Sequencing of the ham34 gene to investigate its function and expression regulatory elements.

Main Results:

  • Five distinct classes of abundant mRNA transcripts were identified, representing over 20% of the total poly(A)+ RNA.
  • Hsp70 and ham34 mRNAs were constitutively expressed, while ham9 and ham12 were specific to spores/germinating spores, and ham37/ham27 to germinating spores.
  • Gene families varied in size, with one clone corresponding to an 11-member gene family.
  • The ham34 gene was sequenced, revealing potential for high-level gene expression.

Conclusions:

  • Germinating B. lactucae spores possess a unique transcriptome with several highly abundant and stage-specific mRNAs.
  • These abundant transcripts, particularly ham34, offer potential for developing gene expression tools for B. lactucae transformation.
  • Understanding these molecular mechanisms is crucial for developing effective disease management strategies against lettuce downy mildew.

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