Pathogen Challenge, Salicylic Acid, and Jasmonic Acid Regulate Expression of Chitinase Gene Homologs in Pine

Abstract

To better understand the molecular regulation of defense responses in members of the genus Pinus, we tested the expression of various chitinase homologs in response to pathogen-associated signals. PSCHI4, a putative extracellular class II chitinase, was secreted into liquid medium by pine cells and was also secreted by transgenic tobacco cells that ectopically expressed pschi4. Extracellular proteins of pine were separated by isoelectric focusing; PSCHI4 was not associated with fractions containing detectable beta-N-acetylglucosaminidase or lysozyme activities. However, other fractions contained enzyme activities that increased markedly after elicitor treatment. The pschi4 transcript and protein accumulated in pine seedlings challenged with the necrotrophic pathogen Fusarium subglutinans f. sp. pini, with the protein reaching detectable levels in susceptible seedlings concomitant with the onset of visible disease symptoms. Additional chitinase transcripts, assigned to classes I and IV based on primary sequence analysis, were also induced by pathogen challenge. Jasmonic acid induced class I and class IV but not class II chitinase, whereas salicylic acid induced all three classes of chitinase. These results show that multiple chitinase homologs are induced after challenge by a necrotrophic pathogen and by potential signaling molecules identified in angiosperms. This suggests the potential importance of de novo pathogenesis-related (PR) gene expression in pathogen defense responses of pine trees.

Evaluating methyl jasmonate for induction of resistance to Fusarium oxysporum, F. circinatum and Ophiostoma novo-ulmi

“…Elicitor compounds affect the synthesis of chemical compounds in plants, but this will result in constraints in carbon allocation and ultimately with reduce plant Evaluating methyl jasmonate for induction of resistance growth or even stop the shoot elongation after the elicitor treatment (Heijari et al, 2005), as observed here. MeJA increased the resin duct density of our seedlings, but despite the general effectiveness of traumatic ducts to contain and reduce damages caused by insects and pathogens (Phillips and Croteau, 1999), F. circinatum is able to tolerate the resin and even stimulate its production on pine trees (Davis et al, 2002;Kim et al, 2010). Thus, even if an increase of resin duct density was observed, F. circinatum would be able to surpass this inducible defense strategy.…”

“…Such interaction may be especially evident in young seedlings where growth during an early establishment phase is likely to be an important component of competitive ability. Resin production is the most familiar and visible component of pine defense (Davis et al, 2002;Kim et al, 2010). It was recently observed that the relative resin production of P. nigra was much lower in 1-than in 2-year-old seedlings, suggesting that the younger trees allocated a lower proportion of the carbon budget to resin synthesis (Wainhouse et al, 2009).…”

Expression and β-glucan binding properties of Scots pine (Pinus sylvestris L.) antimicrobial protein (Sp-AMP)

“…2). The accumulation of SA in response to elicitors and pathogen challenge was earlier shown in pine (Davis et al 2002). SA is furthermore known to induce specific sets of PR genes (Pieterse and van Loon 1999) prior to the establishment of systemic acquired resistance (Grant and Lamb 2006).…”

Diverse chitinases are invoked during the activity-dormancy transition in spruce

“…In the same study, proteins encoded by P. glauca × engelmannii class II and class IV chitinase cDNAs nearly identical to Pg_GQ03904_P01.1 and Pg_GQ03206_D15.1, respectively, as well as several cluster 1/class VII P. glauca × engelmannii and Pinus contorta (lodgepole pine) chitinase cDNAs did not display chitinolytic activity (Kolosova et al 2014). Davis et al (2002) also reported class II Pinus elliottii (slash pine) and Pinus taeda (loblolly pine) chitinases that lacked chitinolytic activity. Kolosova et al (2014) demonstrated that while only class I chitinases exhibited measureable chitinolytic activity, class I, class II, and class IV interior spruce chitinases were upregulated in response to fungal pathogens (Leptographium abietinum) and weevils (Pissodes strobi).…”

“…Pathogen-responsive chitinases often belong to classes I and IV (e.g., SelaBuurlage et al 1993;Davis et al 2002;Passarinho and de Vries 2002;Hietala et al 2004;Islam et al 2010;Kolosova et al 2014) and generally exhibit diagnostic active site residues (Holm and Sander 1994;Hart et al 1995), CBDs (Iseli et al 1993), and a signal peptide targeting the proteins to the secretory pathway (Nielsen et al 1997).…”