Differential expression of multiple PR10 proteins in western white pine following wounding, fungal infection and cold-hardening

Herein the wound-induced expression of a set of PR10 genes (PmPR10) from Pinus monticola (Dougl. Ex D. Don) is described. Thirteen different PmPR10 cDNAs were isolated and their nucleotide sequences were determined from wounded needles. Northern blot analysis showed that PmPR10 gene expression was activated with both local and systemic responses after wounding, and the accumulation of PmPR10 transcript was much more abundant and rapid in wounded needles than in unwounded tissues. Western immunoblot analysis demonstrated that PmPR10 protein synthesis was activated upon wounding, suggesting that the expression of the wound-activated PmPR10 gene was regulated at the transcription level. In wounded needles, the PR10 protein level increased from day 1 to day 8 after treatment. Western immunoblot analysis following isoelectric focusing and two-dimensional electrophoresis revealed that nine PmPR10 proteins accumulated to different extents after wounding. These proteins have a molecular mass of about 18 kDa with different isoelectrical points ranging from 5.2 to 6.0. Wound-inducible PmPR10 proteins were differentially expressed in response to cold-hardening and fungal infection. The wound-induced PmPR10 protein accumulation was enhanced by the wound-signal compound methyl jasmonate and okadaic acid, a specific inhibitor of type 1 or type 2 A serine/threonine protein phosphatases. However, it was partially suppressed by salicylic acid and abscisic acid. These data provide an opportunity to elucidate further the signal transduction pathway involved in the activation of PmPR10 protein synthesis in the defence response of white pine against mechanical injury.