Cloning and targeted disruption of two polygalacturonase genes in Penicillium olsonii

Abstract

The filamentous fungus Penicillium olsonii secretes several polygalacturonases (PGs) with molecular masses of about 47 kDa. These enzymes consist of several basic and acidic isoforms, with dominant activities at pI 4.5 and pI 7.9. Two polygalacturonase genes, pg1 and pg2, have been cloned. The corresponding enzymes, PG1 and PG2, consist of 370 and 380 amino acids, respectively, and show significant similarities to endo-polygalacturonases from other filamentous fungi. Targeted disruption of pg1 resulted in the elimination of all basic PG isoforms. In contrast, disruption of pg2 reduced, but did not eliminate the acidic PG activities. The PGs of P. olsonii must therefore be encoded by a gene family of at least three genes. Induction studies with various carbon sources revealed that the acidic and basic isoforms are differentially regulated. Pectin is the best inducer of the acidic PG isoforms. The basic isoforms, however, are best induced by monosaccharides like glucose, K-L-rhamnose and K-L-arabinose. ß

Carbon, nitrogen and pH regulate the production and activity of a polygalacturonase isozyme produced byPenicillium expansum

“…Our findings are consistent with those reported for Phomopsis cucurbitae, a postharvest pathogen of cantaloupe fruit, in which both optimal PG activity and fungal growth Archives of Phytopathology and Plant Protection 1107 did not coincide (Zhang et al 1999). They are also congruent with other studies showing that fungal PGs are induced by their substrate, and exhibit activity on carbon sources other than pectin (Wagner et al 2000). Nitrogen source also influenced PG activity with the most statistically significant increase occurring in culture when the fungus was grown with pectin and ammonium chloride.…”

Interaction of Sclerotinia sclerotiorum with Brassica napus: cloning and characterization of endo- and exo-polygalacturonases expressed during saprophytic and parasitic modes

“…An exo-polygalacturonase was also isolated from F. oxysporum (Garcia-Maceira et al, 2000). Evidence to support the notion that PGs are directly involved in pathogenic processes has recently been provided by targeted mutagenesis in Aspergillus flavus (Shieh et al, 1997), B. cinerea (ten Have et al, 1998), F. oxysporum (Garcia-Maceira et al, 2001), and Penicillium olsonii (Wagner et al, 2000).…”

Brassica napus possesses an expanded set of polygalacturonase inhibitor protein genes that are differentially regulated in response to Sclerotinia sclerotiorum infection, wounding and defense hormone treatment

“…A set of 19 PG genes encoding enzymes with seemingly diverse biochemical properties were isolated from Phytophthora cinnamomi (Gotesson et al 2002). Targeted mutagenesis in Aspergillus Xavus (Shieh et al 1997), B. cinerea (ten Have et al 1998), Fusarium oxysporum (Garcia-Maceira et al 2001) and Penicillium olsonii (Wagner et al 2000) has also provided direct evidence to support this concept that PGs are important pathogenicity determinants.…”