บทคัดย่องานวิจัย

หมวดหมู่ : ฐานข้อมูลงานวิจัย

Catalane activity, protein accumulation, and expression during postharvest senescence of carnations and in response to inhibitors of ethylene synthesis or action

Altman, Steven A.

Thesis of, Ph.D., University of Maryland College Park, 1991, 278 pages.

1991

บทคัดย่อ

CATALASE ACTIVITY, PROTEIN ACCUMULATION, AND EXPRESSION DURING POSTHARVEST SENESCENCE OF CARNATIONS AND IN RESPONSE TO INHIBITORS OF ETHYLENE SYNTHESIS OR ACTION (DIANTHUS CARYOPHYLLUS).

Catalase, a tetrameric hemeoprotein, is ubiquitously present in aerobic cytochrome-bearing plant cells.  The role of catalase in postharvest senescence of plant tissues is not well characterized.  Senescence-associated increases in catalase activity have been observed in many plant tissues, consistent with the view of senescence as an oxidative phenomenon culminating in loss of cell integrity.

 Postharvest changes in catalase activity, in accumulation of catalase protein, and in mRNA accumulation, both in untreated control flowers and in flowers treated with inhibitors of ethylene synthesis or action, were characterized in white Sim carnations (Dianthus caryophyllus L.  cv Elliott's White).  Carnations served as a model system for these studies because their climacteric-type postharvest physiology is similar to that of many major horticultural food crops.

 Endogenous catalase activity in carnation petal apices, determined polarographically, was found to increase within 4-6 hr of harvest, reaching peak activity at approximately 5 d postharvest and declining thereafter.  Aminotriazole and silver thiosulfate anionic complex repressed the overall level and abolished the postharvest increase in catalase activity.  Aminoethoxyvinylglycine did not affect the level or increase in catalase activity but delayed time to peak activity until approximately 10 d postharvest.

 Subsequently, two electrophoretically distinct immunoreactive catalase isoforms were identifiedIn untreated petal tissue, accumulation of the predominant low molecular weight isoform (LMW) increased beginning at harvest, reaching maximal accumulation at approximately 5 d postharvest, coincident with the observed peak of catalase activityAccumulation of a low abundance high molecular weight isoform (HMW) initially remained unchanged, then increased to maximal accumulation at approximately 9 d postharvest coincident with the respiratory climacteric.  Data obtained from treatment of petal tissues with ethylene synthesis or action inhibitors suggests that changes in accumulation of the HMW catalase isoform may be regulated by endogenous ethylene.

 A heterologous cDNA clone encoding a low specific activity catalase was used to identify a 2.8 kb carnation mRNA which may encode the HMW catalase isoform in both petal apices and in stem internode tissue.  In untreated petal tissue, this message is apparently rare, and may account for the low accumulation of HMW observed during carnation postharvest senescence.