Regulation of Constitutively Expressed and Induced Cutinase Genes by Different Zinc Finger Transcription Factors inFusarium solani f. sp. pisi(Nectria haematococca)

Abstract

Cutin monomers, generated by the low levels of constitutively expressed cutinase, induce high levels of cutinase that can help pathogenic fungi to penetrate into the host through the cuticle whose major structural polymer is cutin. We cloned three highly homologous cutinase genes, cut1, cut2, and cut3, from Fusarium solani f. pisi (Nectria haematococca). Amino acid sequence deduced from the nucleotide sequence of cut1 and cut2/3 matched with that of the peptides from cutinase 1 and cutinase 2, respectively, isolated from F. solani pisi grown on cutin as the sole carbon source. Induction of ␤-glucuronidase gene fused to the promoters of the cutinases integrated into F. solani pisi genome indicates that cut2 is constitutively expressed and induced under starvation, whereas cut1 is highly induced by cutin monomers. A palindrome binding protein (PBP) previously cloned binds only to palindrome 1 of cut1 promoter but not palindrome 1 of cut2/3 which contains two base substitutions. PBP is thought to interfere with the binding of CTF1␣, the transcription factor involved in induction, to cut1 promoter and thus keep cut1 gene repressed until induced by cutin monomers. Because PBP cannot bind palindrome 1 of cut2, this gene is not repressed. CTF1␣ does not transactivate cut2 promoter. A new Cys 6 Zn 2 motif-containing transcription factor, CTF1␤, that binds palindrome 2 was cloned and sequenced. In yeast, CTF1␤ transactivates cut2 promoter but not cut1 promoter unless its palindrome 1 is mutated, unlike CTF1␣ which transactivates cut1. Thus, CTF1␤ is involved in the constitutive expression of cut2 that causes production of low levels of cutin monomers that strongly induce cut1 using CTF1␣ as the transcription factor.Fungal infection of plants can be assisted by extracellular cutinases that help the pathogen penetrate through the outermost cuticular barrier of the host (1, 2). Conidia of highly virulent pathogens, which can directly penetrate through the cuticle, have low levels of cutinase that release small amounts of cutin monomers when the conidia contact the host surface (3). These monomers transcriptionally activate the expression of an inducible cutinase gene that is responsible for the production of high levels of cutinase that assist the infection peg to gain entry into the host through the cuticle (4). A cis element essential for the inducible expression of cutinase gene was found to be located at Ϫ159 bp in the promoter of this gene (5) in Fusarium solani f. pisi (Nectria haematococca). In this region, two overlapping palindromes were found. Palindrome 2 was found to be necessary for the inducible cutinase gene expression (5). A protein that binds the palindromic region, called palindrome binding protein (PBP), 1 (6) and a cutinase transcription factor 1␣ (CTF1␣), which selectively binds palindrome 2 and transactivates the cutinase promoter (7), have been cloned. CTF1␣, a 101-kDa protein, contains a Cys 6 Zn 2 binuclear cluster motif, sharing homology to the Cys 6 Zn 2 binuclear cluster DNA-binding domains of tr...

Regulatory Genes Controlling Fatty Acid Catabolism and Peroxisomal Functions in the Filamentous Fungus Aspergillus nidulans

“…Of particular note was the finding that the predicted proteins were highly similar to the cutinase transcription factors CTF␣ and CTF␤ of Nectria hematococca. These proteins have been found to bind to sequences in the 5Ј region of cutinase genes in this plant pathogen (43,44). Cutin is a polymer containing hydroxy-oleate, strongly suggesting a connection with fatty acid breakdown.…”

“…(Fig. 2C), the choice of DNA probes for analysis was guided by studies with these proteins (43,44). As summarized in Fig.…”

Expressed sequence tag (EST) analysis of two subspecies of Metarhizium anisopliae reveals a plethora of secreted proteins with potential activity in insect hosts

“…Likewise, the plant pathogen Fusarium solani penetrates plant cell walls using cutinase, produced in response to soluble monomers released by constitutive production of cutinase (Li et al, 2002). Production by M. anisopliae of homologues to cutinase transcription factor 1 (AJ272967) and cutinase G-box binding protein (AJ274235) (E 5 3610 276 and 1610 263 , respectively), previously only known to be involved in cutinase induction in F. solani (Li et al, 2002), implies similarities between the regulatory circuitry of these pathogens with very different hosts. As there is no indication of the production of cutinases by M. a. sf.…”

Putative pathogenicity genes of Aspergillus niger in sisal and their expression in vitro

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