PLANT PHYSIOLOGY , Vol 103, Issue 4 1347-1353, Copyright © 1993 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Methyl Jasmonate Induces Papain Inhibitor(s) in Tomato Leaves
C. J. Bolter
Agriculture Canada Research Centre, 1391 Sandford Street, London, Ontario, N5V 4T3, Canada
Leaves of 18- to 24-d-old tomato (Lycopersicon esculentum) plants exposed
to gaseous methyl jasmonate (MJ) for 24 h at 30[deg]C in continuous light
contained high levels of soluble protein that inhibited papain.
Chromatographic analysis demonstrated that the active protein had a
molecular mass of 80 to 90 kD. Induction of papain inhibitor was directly
related to the concentration of air-borne MJ up to a maximum of 0.1 [mu]L
MJ per treatment and depended on the duration of exposure up to 18 h.
Inhibitor activity in plants treated for less than 18 h increased with time
after treatment. Levels remained constant for up to 4 d after treatment,
after which time activity decreased. The youngest leaf, leaf 5,
consistently lost activity at a faster rate than older, lower leaves.
Inhibitor concentration in all leaves was reduced to minimum levels by 11 d
after MJ treatment, but did not return to control levels. Treatment with MJ
in the dark did induce inhibitor activity, but at a significantly lower
rate. Polyclonal antibodies raised to purified potato tuber skin cysteine
proteinase inhibitors (CPI) cross-reacted with the tomato inhibitor,
suggesting that the tomato papain inhibitor and the potato CPI are closely
related. No papain inhibitor activity was observed in extracts from wounded
tomato leaves, nor was there any immunoreactivity with antibodies raised to
potato tuber skin CPI.
