Mir1 is highly upregulated and localized to nuclei during infectious hyphal growth in the rice blast fungus

Lei Li, Sheng Li Ding, Amir Sharon, Marc Joel Orbach, Jin Rong Xu

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Rice blast, caused by Magnaporthe grisea, is a devastating disease of rice throughout the world. Many recent molecular studies have focused on the early infection stages, but our knowledge about molecular events at the infectious hyphae stage is limited. In this study, 750 hygromycin-resistant transformants were isolated by transforming M. grisea Guy11 with a promoterless enhanced green fluorescent protein (EGFP) construct. In one of the transformants, L1320, EGFP signals were observed in the nuclei of infectious hyphae. The transforming vector was inserted in a predicted gene named MIR1 and resulted in a Mir1 1-107-EGFP fusion. Mir1 is a low-complexity protein with no known protein domain and has no homolog in GenBank or other sequenced fungal genomes. Quantitative real-time reverse-transcriptase polymerase chain reaction analysis and expression assays of MIR1-EGFP fusion constructs indicated that the expression of MIR1 was highly induced during plant infection. Deletion analyses identified a 458-bp region that was sufficient for the MIR1 promoter activity. Further characterization revealed that a 96-bp sequence was essential for the enhanced in planta expression. MIR1 is an M. grisea-specific gene that is highly conserved among the field isolates belonging to the M. grisea species complex. The mir1 mutants had no obvious defects in appressorial penetration and rice infection. When overexpressed with the RP27 promoter, nuclear localization of the Mir1-EGFP fusion was observed in conidia and vegetative hyphae. These data suggest that the expression but not the nuclear localization of MIR1 is specific to infectious hyphae and that reporter genes based on MIR1 may be suitable for monitoring infectious growth in M. grisea.

Original languageEnglish (US)
Pages (from-to)448-458
Number of pages11
JournalMolecular Plant-Microbe Interactions
Volume20
Issue number4
DOIs
StatePublished - Apr 2007

Fingerprint

Magnaporthe
Magnaporthe grisea
blast disease
Fungi
green fluorescent protein
Hyphae
hyphae
Genes
fungi
Growth
Fusion reactions
Fungal Genome
Infection
promoter regions
infection
rice
Fungal Spores
Polymerase chain reaction
RNA-Directed DNA Polymerase
Nucleic Acid Databases

Keywords

  • Appressorium
  • Fungus-plant interaction
  • Pathogenesis

ASJC Scopus subject areas

  • Microbiology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Biotechnology

Cite this

Mir1 is highly upregulated and localized to nuclei during infectious hyphal growth in the rice blast fungus. / Li, Lei; Ding, Sheng Li; Sharon, Amir; Orbach, Marc Joel; Xu, Jin Rong.

In: Molecular Plant-Microbe Interactions, Vol. 20, No. 4, 04.2007, p. 448-458.

Research output: Contribution to journalArticle

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abstract = "Rice blast, caused by Magnaporthe grisea, is a devastating disease of rice throughout the world. Many recent molecular studies have focused on the early infection stages, but our knowledge about molecular events at the infectious hyphae stage is limited. In this study, 750 hygromycin-resistant transformants were isolated by transforming M. grisea Guy11 with a promoterless enhanced green fluorescent protein (EGFP) construct. In one of the transformants, L1320, EGFP signals were observed in the nuclei of infectious hyphae. The transforming vector was inserted in a predicted gene named MIR1 and resulted in a Mir1 1-107-EGFP fusion. Mir1 is a low-complexity protein with no known protein domain and has no homolog in GenBank or other sequenced fungal genomes. Quantitative real-time reverse-transcriptase polymerase chain reaction analysis and expression assays of MIR1-EGFP fusion constructs indicated that the expression of MIR1 was highly induced during plant infection. Deletion analyses identified a 458-bp region that was sufficient for the MIR1 promoter activity. Further characterization revealed that a 96-bp sequence was essential for the enhanced in planta expression. MIR1 is an M. grisea-specific gene that is highly conserved among the field isolates belonging to the M. grisea species complex. The mir1 mutants had no obvious defects in appressorial penetration and rice infection. When overexpressed with the RP27 promoter, nuclear localization of the Mir1-EGFP fusion was observed in conidia and vegetative hyphae. These data suggest that the expression but not the nuclear localization of MIR1 is specific to infectious hyphae and that reporter genes based on MIR1 may be suitable for monitoring infectious growth in M. grisea.",
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