CHELATOR USED IN PECTIN EXTRACTION TRIGGERS ETHYLENE PRODUCTION BY TOMATO FRUIT

In our search for an endogenous ethylene trigger from tomato (Lycopers icon esculentum Mill. cv Rutgers) fruit eel wall alkaline soluble pect in (ASP), we purified an active component using DEAE-Sepharose chromat ography followed by elution on Bio-Gel P-100 or Superose 12. The purif ied active fraction produced a single band on silver-stained SDS-PAGE of approximately M(r) 20000. Using two-dimensional proton-proton and p roton-carbon correlation spectroscopy, we identified the repeating sub unit as rans-1,2-diamino-cyclohexane-N,N,N',N'-tetraacetic acid (CDTA) , a chelator used to extract ASP. Although the ASP undergoes extensive dialysis during its extraction which should remove CDTA, the CDTA app arently forms a large molecular weight polymer which does not diffuse out of the dialysis tubing. Infiltration of commercially prepared CDTA into mature green tomato fruit stimulated ethylene production. The et hylene stimulatory effect of CDTA was not affected by the presence of equimolar amounts of CaCl2, or nmol g(-1) amounts of the calcium chann el blockers, nifedipine or verapamil. EDTA, EGTA, and diethylenetriami nepentaacetic acid, other divalent cation chelators, also stimulated e thylene production when they were infiltrated into tomato fruit. Neith er the purified material nor commercial CDTA stimulated ethylene produ ction when they were infiltrated into leaf tissue.