Molecular and General Genetics MGG

, Volume 243, Issue 3, pp 277–285

Nitrogen limitation induces expression of the avirulence gene avr9 in the tomato pathogen Cladosporium fulvum

  • G. F. J. M. Van den Ackerveken
  • R. M. Dunn
  • A. J. Cozijnsen
  • J. P. M. J. Vossen
  • H. W. J. Van den Broek
  • P. J. G. M. De Wit
Original Paper

DOI: 10.1007/BF00301063

Cite this article as:
Van den Ackerveken, G.F.J.M., Dunn, R.M., Cozijnsen, A.J. et al. Molec. Gen. Genet. (1994) 243: 277. doi:10.1007/BF00301063

Abstract

The avirulence gene avr9 of the fungal tomato pathogen Cladosporium fulvum encodes a race-specific peptide elicitor that induces the hypersensitive response in tomato plants carrying the complementary resistance gene Cf9. The avr9 gene is not expressed under optimal growth conditions in vitro, but is highly expressed when the fungus grows inside the tomato leaf. In this paper we present evidence for the induction of avr9 gene expression in C. fulvum grown in vitro under conditions of nitrogen limitation. Only growth medium with very low amounts of nitrogen (nitrate, ammonium, glutamate or glutamine) induced the expression of avr9. Limitation of other macronutrients or the addition of plant factors did not induce the expression of avr9. The induced expression of avr9 is possibly mediated by a positive-acting nitrogen regulatory protein, homologous to the Neurospora crassa NIT2 protein, which induces the expression of many genes under conditions of nitrogen limitation. The avr9 promoter contains several putative NIT2 binding sites. The expression of avr9 during the infection process was explored cytologically using transformants of C. fulvum carrying an avr9 promoter-β-glucuronidase reporter gene fusion. The possibility that expression of avr9 in C. fulvum growing in planta is caused by nitrogen limitation in the apoplast of the tomato leaf is discussed.

Key words

Cladosporium fulvumFungal avirulence geneNitrogen limitationNitrogen regulation

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • G. F. J. M. Van den Ackerveken
    • 1
    • 2
  • R. M. Dunn
    • 1
  • A. J. Cozijnsen
    • 1
  • J. P. M. J. Vossen
    • 1
  • H. W. J. Van den Broek
    • 2
  • P. J. G. M. De Wit
    • 1
  1. 1.Department of PhytopathologyAgricultural University WageningenEE WageningenThe Netherlands
  2. 2.Department of GeneticsAgricultural University WageningenHA Wageningen
  3. 3.Institut des Sciences VégétalesGif-sur-YuetteFrance
  4. 4.School of SciencesStaffordshire UniversityStoke-on-TrentUK