A novel role of PR2 in abscisic acid (ABA) mediated, pathogen-induced callose deposition in Arabidopsis thaliana

• Pathogenesis-related protein 2 (PR2) is known to play a major role in plant defense andgeneral stress responses. Resistance against the fungal pathogen Leptosphaeria maculans inArabidopsis requires abscisic acid (ABA), which promotes the deposition of callose, a b-1,3-glucan polymer. Here, we examined the role of PR2 in callose deposition in relation to ABAtreatment and challenge with L. maculans and Pseudomonas syringae. Characterization of PR2-overexpressing plants and the knockout line indicated that PR2negatively affects callose deposition. Recombinant PR2 purified from Pichia pastoris showedcallose-degrading activity, and a considerable reduction in the callose-degrading activity wasobserved in the leaf extract of the PR2 knockout line compared with the wild-type. ABA pretreatment before challenge with L. maculans concomitantly repressed PR2 andenhanced callose accumulation. Likewise, overexpression of an ABA biosynthesis geneNCED3 resulted in reduced PR2 expression and increased callose deposition. We propose that ABA promotes callose deposition through the transcriptional repression ofPR2 in Arabidopsis challenged by L. maculans and P. syringae. Callose by itself is likely to actantagonistically on salicylic acid (SA) defense signaling, suggesting that PR2 may function as amodulator of callose- and SA-dependent defense responses.

Ämnesord

LANTBRUKSVETENSKAPER  -- Bioteknologi med applikationer på växter och djur -- Växtbioteknologi (hsv//swe)

AGRICULTURAL SCIENCES  -- Agricultural Biotechnology -- Plant Biotechnology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

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