Polygalacturonase, Pectate Lyase and Pectin Methylesterase Activity in Pathogenic Strains of Phytophthora capsici Incubated under Different Conditions

Abstract

Pectolytic enzymes are found mainly in fungi and bacteria. The most widely occurring enzymes are polygalacturonase (PGs), pectin methylesterase (PMEs) and pectate lyase (PLs) produced during the infection process and during culturing. The secretion of these enzymes results in the disorganization of the plant cell walls, which is responsible for the pathogenicity of the pathogens. These enzymes degrade the pectin of plants causing maceration of plant tissues and the enzyme activity increases under favourable environmental conditions. We have found that Phytophthora capsici, a pathogenic oomycete, produces levels of these three enzymes equal to those produced by soft-rotting Erwinia chrysanthemi. The activity of PGs, PLs and PMEs was investigated at the optimum temperature, pH and ionic strength in highly pathogenic P. capsici strains cultivated in two kinds of liquid medium containing either crude pepper extracts plus pectin or pectin as the carbon source. Virulence tests and enzymes activity showed that there was a high correlation between the enzyme activity and the pathogenicity of P. capsici. The effects of different carbon sources on the enzyme activity showed that pepper extract plus pectin was the best source for the carbon source.

Structure and Properties of a Non-processive, Salt-requiring, and Acidophilic Pectin Methylesterase from Aspergillus niger Provide Insights into the Key Determinants of Processivity Control

“…1). As well as being ubiquitous in plants, and frequently manifesting in a staggering number of isoforms (more than 66 for Arabidopsis thaliana) (8,10), PMEs are found in phytopathogenic bacteria and fungi (17)(18)(19)(20)(21)(22)(23)(24)(25)(26) and in Archaea (especially Halobacteriaceae (27)), and they have also been observed in the genomes of several phytophagous insects (28 -30) and in human gut microflora (31). Recently, plant pollen PMEs have been identified as a key human allergen (32,33).…”

Isolation of nine Phytophthora capsici pectin methylesterase genes which are differentially expressed in various plant species

“…Previous studies revealed that PMEs was a highly specific enzyme for the D-galacturonan structure and its activity was affected by several factors such as pH, ionic strength and temperature [39]. For example, Aspergillus niger PMEs had an optimal pH of 5 for enzymatic activity [40], whereas the pH optimum for P. capsici PMEs was 6.5 [10]. In addition, pectin and pectic acid in plant hosts induced microorganisms to produce PME.…”

“…Highvirulent P. capsici strain SD33 [5,10] was used in these studies, and genomic DNA was extracted as previously described [21]. A genomic library of P. capsici was constructed as previously described [11] and screened using five pairs of degenerate primers (Table 1) designed ba- Table 1.…”

“…Little is known of the activity of pectin methylesterase in P. capsici except that it was first detected during the infection process and its activity was found during all steps of infection [10]. In these studies, we wish to characterize expression patterns that may be observed in different hosts, which could be beneficial for further analysis of P. capsici infection and shed light on why P. capici has a broad host range.…”

“…Pectin methylesterase (PME; EC 3.1.1.11) removes the methyl group from esterified galacturonic acid residues in pectin chains [9]. Our previous studies revealed that the CWDEs were contributing to virulence of P. capsici during the course of infection [10,11] in a manner similar to that of CWDEs from bacterial [12,13] and fungal pathogens [14 − 17]. These studies have shown that pectinases, which are among the CWDEs secreted by P. capsici, play an important role in the infection process.…”