Expression of β-1,3-glucanase and chitinase in healthy, stem-rust-affected and elicitor-treated near-isogenic wheat lines showing<i>Sr</i>5-or<i>Sr</i>24-specified race-specific rust resistance
Date de parution
Planta, Springer, 1997/201/2/235-244
Pathogenesis-related expression of the two antifungal hydrolases β-1,3-glucanase (EC 18.104.22.168) and chitinase (EC 22.214.171.124) was studied in wheat (<i>Triticum aestivum</i> L.) as part of the defence response to stem rust (<i>Puccinia graminis</i> f.sp.<i>tritici</i>; Pgt), mediated by the semi-dominantly acting resistance genes <i>Sr5</i> and <i>Sr24</i>. Complete resistance (infection type 0), mediated by the <i>Sr5</i> gene in cultivar Pre-<i>Sr5</i>, closely correlates with the hypersensitive response of penetrated cells at early stage of the interaction, when the first haustorium is formed. In contrast, cultivar Pre-Sr24 shows intermediate resistance (infection type 2–3) which is not directly linked to cell death. In both cases, the plant response included a rapid increase in β-1,3-glucanase activity between 24 and 48 h after inoculation. One main extracellular 30-kDa isoform of β -1,3-glucanase was present in both lines, as shown by polyacrylamide-gel electrophoresis. Two additional minor isoforms (32 and 23 kDa) were detected only in Pre- <i>Sr24</i>, and only at later time points. Increased enzyme activity and the appearance of new isoforms in the resistant lines was preceded by accumulation of mRNAs encoding β-1,3-glucanases and chitinases. However, there were no changes in chitinase activity or isoforms. A high constitutive level of chitinase activity was observed in all wheat genotypes. Serological studies indicated the presence of a class 11 chitinase of 26 kDa. Accumulation of β-1,3-glucanase and chitinase transcripts was detected before the pathogen penetrated the leaves through stomata and approximately 16 h before the typical hypersensitive response was observed, indicating that signal(s) for defense gene activation were recognised by the host plant long before a tight contact between the pathogen and a host cell is established. A glycoprotein (Pgt elicitor) derived from hyphal walls, strongly induced β-1,3-glucanase. We discuss the possible role of the elicitor in the early signalling mediating <i>Sr5</i> and <i>Sr24</i>-specified resistance in wheat.
Type de publication
Resource Types::text::journal::journal article