Cloning, Expression and Characterization of Protein Elicitors from the Soyabean Pathogenic Fungus Phytophthora sojae

Abstract

The oomycete Phytophthora sojae is a severe pathogen of soybean. Several resistance genes against races of P. sojae exist in soybean but the nature of corresponding avirulence genes is unknown. Clones encoding four different isoforms of a protein elicitor from P. sojae (sojein 1–4) belonging to the class of acidic α‐elicitins have been isolated. These 98 amino acid proteins show high homology to elicitins from other Phytophthora species. The different sojein isoforms were expressed in Escherichia coli as His‐tagged fusion proteins. Purified sojein as well as recombinant sojein isoforms induce hypersensitive reaction (HR)‐like lesions in tobacco but are not active as race‐specific elicitors in soybean. However all sojein isoforms induce defence‐related genes like those encoding phenylalanine ammonia lyase, glutathione‐S‐transferase and chalcone synthase in tobacco and soybean plants and cell cultures. It is concluded that sojeins contribute to the induction of defence responses but that they are not involved in race specific recognition of the P. sojae races by soybean plants.

Variation in structure and activity among elicitins from Phytophthora sojae

“… * The SOJA family includes SOJA‐2 (identical to Sojein2 ; AJ007859), and nearly identical sequences SOJA‐1 ( Sojein1 ; AJ007858), SOJA‐3 ( Sojein3 ; AJ007860) and SOJA‐4 ( Sojein4 ; AJ007858) ( Becker et al ., 2000 ). …”

“…The activities of the various elicitin domains in inducing hypersensitive response (HR)‐like symptoms in Nicotiana species are shown as positive (+), negative (–), or not determined (ND). Results are summarized from this investigation or from previous studies for SOJA‐2 ( Becker et al ., 2000 ; Mao and Tyler, 1996 ). Expression in mycelia cultures (MY), infected plant tissue (IN), and zoospores (ZO) was determined from the analysis of expressed sequence tags (shown in detail in Fig.…”

Stigmasterol and Cholesterol Regulate the Expression of Elicitin Genes in Phytophthora sojae

“…Primer Specificity for Elicitin Amplification P. sojae contains at least nine elicitin genes (Qutob et al 2003), two of which are class-I and named SOJA and SOJB (referred to as sojein in Mao andTyler 1996 andBecker et al 2000). The letters A and B following SOJ further classify the elicitins according to their isoelectric (pI) points as either acidic (A, pI<5) or basic (B, pI>5), depending on the total number of Lys residues present in the elicitin domain Qutob et al 2003).…”

“…The letters A and B following SOJ further classify the elicitins according to their isoelectric (pI) points as either acidic (A, pI<5) or basic (B, pI>5), depending on the total number of Lys residues present in the elicitin domain Qutob et al 2003). Moreover, four isotypes of the SOJA gene are present, (originally named sojein 1-4 in Mao andTyler 1996 andBecker et al 2000) that differ from each other by a few amino acid substitutions within the elicitin domain, which results in a slightly different amino acid content. Primers for the SOJA and SOJB elicitin genes were designed from their cDNA sequences available on the National Center for Biotechnology Information (NCBI) web-site (Table 1), whereas primers for the internal control Actin gene (ActA) were designed from sequences of the gene available for P. sojae on the US Department of Energy's Joint Genome Initiative (JGI) web-site (Table 1).…”

Distribution and Expression of Elicitin Genes in the Interspecific Hybrid OomycetePhytophthora alni

“…Although elicitin genes are not appropriate for phylogenetic studies because of their multigenic family feature, they can be used as a tool for identification purposes since the amino acid sequence of a given elicitin may provide a signature at the species level (25). In addition, the 3Ј untranslated regions (3ЈUTRs) of class I elicitin genes are strictly conserved within an individual species but diverge between species to such an extent that sequence alignment is almost impossible (1,6,11;Panabières et al,unpublished results).…”