Disruption of Botrytis cinerea Pectin Methylesterase Gene Bcpme1 Reduces Virulence on Several Host Plants

Abstract

The pectinolytic enzyme pectin methylesterase (PME) hydrolyses pectin in methanol and polygalacturonic acid. In the expressed sequence tag library of Botrytis cinerea T4, we identified a 1,041 bp Bcpme1 cDNA potentially encoding a 346-amino acid protein of 37 kDa showing 46.8% identity with Aspergillus sp. PMEs. Bcpme1 is a single copy gene and is similarly expressed in glucose and pectin containing media. To evaluate the role of Bcpme1 in Botrytis cinerea virulence, a mutant in Bcpme1 was generated by gene disruption. The Bcpme1 mutant showed similar growth on rich medium but reduced growth on pectin medium. Two isozymes of pI 7.4 and 7.1 were detected in pectin liquid-culture supernatants of wild-type strain Bd90 analyzed by isoelectric focusing-polyacrylamide gel electrophoresis, while those of Bcpme1 mutant possessed only the pI 7.1 isozyme. BCPME1, the pI 7.4 isozyme, is the major PME activity, as PME activity is 75% reduced in Bcpme1 mutant. Moreover, the Bcpme1 mutant was less virulent on apple fruits, grapevine, and Arabidopsis thaliana leaves. Those phenotypes were complemented by reintroducing a Bcpme1 copy in the Bcpme1 mutant. These results showed that B. cinerea possessed more than one PME-encoding gene and that BCPME1 is an important determinant of B. cinerea virulence.

Identification of soluble secreted proteins from appressoria of Colletotrichum higginsianum by analysis of expressed sequence tags

“…We also identified a putative pectin methyl esterase that could assist host penetration. Demethylation of highly esterified cell wall pectins may be a prerequisite for their degradation by fungal endopolygalacturonases (Lionetti et al, 2007), and a pectin methyl esterase was required for the full virulence of Botrytis cinerea on Arabidopsis (Valette-Collet et al, 2003). Furthermore, our analysis suggested that C. higginsianum secretes a putative lignin peroxidase.…”

Pectin Biosynthesis Is Critical for Cell Wall Integrity and Immunity in Arabidopsis thaliana

“…This was not unexpected because B. cinerea is known to interact with pectin as part of its infection strategy. It secretes various pectin-degrading enzymes early during infection and requires some of these enzymes, including PG1, PG2, and PME1, for full virulence (ten Have et al, 1998;Valette-Collet et al, 2003;Kars et al, 2005b;Espino et al, 2010). Additionally, Arabidopsis plants expressing an antisense construct of the polygalacturonase inhibitor PGIP1 are significantly more susceptible to B. cinerea (Ferrari et al, 2006).…”

“…We hypothesized that plant immunity to B. cinerea might be affected by pectin content in the host cell wall because this pathogen requires polygalacturonases and pectin methylesterases for full virulence (ten Have et al, 1998;Valette-Collet et al, 2003;Kars et al, 2005b;Espino et al, 2010). Because B. cinerea is genetically diverse and has a high diversity of polygalacturonases (Rowe and Kliebenstein, 2007), we measured relative fungal growth at both 2 and 3 d postinoculation (dpi) using 10 different B. cinerea isolates ( Figure 6).…”

Fine mapping, physical mapping and development of diagnostic markers for the Rrs2 scald resistance gene in barley

“…Apart from cellulose and hemicellulose, pectin is the main and the most complex polysaccharide of plant cell walls. Pectinolytic enzymes are among the first to be secreted by plant pathogens and include, polygalacturonases, pectate and pectin lyases, as well as pectinesterases (Alghisi and Favaron 1995;Valette-Collet et al 2003). Plants in turn produce enzymes which can inhibit the activity of microbial enzymes.…”