The regulation of peroxidase activity by gibberellin and auxin in pea stem segments

Abstract

Peroxidase activity in excised stem segments of Pisum sativum L. cv. Progress No. 9 increases linearly during incubation in buffered medium. Gibberellic acid (GA) causes a slight reduction in activity whereas indoleacetic acid (IAA) treatment completely prevents this rise. Excision produces two new cathodic isoperoxidases near the cut ends. Their appearance is prevented by cycloheximide, actinomycin D, and IAA; G A enhances this IAA-induced repression. GA alone stimulates one of the isozymes but does not affect the other one. Peroxidase leakage is stimulated by GA and inhibited by IAA treatment. The activity is entirely confined to the isoperoxidases produced in response to injury.IAA oxidase activity in incubated segments was slightly elevated over that of freshly cut ones. However, differences in activity among hormone treatments were small. IAA oxidase was also demonstrated in growth media and only IAA treatment reduced activity. Both peroxidases in the medium were isolated by column chromatography. Surprisingly, the purified isozymes appear to be essentially devoid of IAA oxidase activity.

Indole-3-Acetic Acid Control on Acidic Oat Cell Wall Peroxidases

“…The reduction in peroxidase activity by exogenously applied IAA has been reported in several plant systems (Gordon and Henderson 1973, Morrow and Jones 1986, Ockerse et al 1965, Ockerse and Mumford 1973, Ros Barceló et al 1989), but only a few reports describe the effect of this auxin on peroxidases from the cell walls (Morrow andJones 1986, Ros Barceló et al 1989). In pea internode sections, intercellular peroxidase activity was decreased by IAA treatment, an effect that correlated inversely with the elongation rate (Morrow and Jones 1986), and application of IAA or 2,4 dichlorophenoxiacetic acid to exponentially growing lupin hypocotyls promoted a reduction in the level of free intercellular peroxidases (Ros Barceló et al 1989).…”

“…Catabolism of IAA through oxidation has been demonstrated to be catalyzed by peroxidases in active growing tissues (Gordon and Henderson 1973, Ockerse and Mumford 1973). Several studies indicated that IAA decreased peroxidase activity in plant tissues in which this auxin induces cell elongation (Morrow and Jones 1986, Ockerse and Mumford 1973, Ros Barceló et al 1989).…”

“…Several studies indicated that IAA decreased peroxidase activity in plant tissues in which this auxin induces cell elongation (Morrow and Jones 1986, Ockerse and Mumford 1973, Ros Barceló et al 1989). The inhibited peroxidases include the IAA oxidase activity shown by certain peroxidase isoforms (Gordon andHenderson 1973, Ockerse andMumford 1973).…”

“…Several studies indicated that IAA decreased peroxidase activity in plant tissues in which this auxin induces cell elongation (Morrow and Jones 1986, Ockerse and Mumford 1973, Ros Barceló et al 1989). The inhibited peroxidases include the IAA oxidase activity shown by certain peroxidase isoforms (Gordon andHenderson 1973, Ockerse andMumford 1973). However, in these reports it is not possible to correlate reduced peroxidase activity by IAA with cell enlargement because most of the studies deal with total peroxidase activity present in crude extracts (Gordon and Henderson 1973, Morrow and Jones 1986, Ockerse and Mumford 1973; rarely has it been demonstrated that the measured peroxidase activity came from the cell walls without intracellular contamination (Morrow and Jones 1986, Ros Barceló et al 1989).…”

“…The inhibited peroxidases include the IAA oxidase activity shown by certain peroxidase isoforms (Gordon andHenderson 1973, Ockerse andMumford 1973). However, in these reports it is not possible to correlate reduced peroxidase activity by IAA with cell enlargement because most of the studies deal with total peroxidase activity present in crude extracts (Gordon and Henderson 1973, Morrow and Jones 1986, Ockerse and Mumford 1973; rarely has it been demonstrated that the measured peroxidase activity came from the cell walls without intracellular contamination (Morrow and Jones 1986, Ros Barceló et al 1989). Peroxidases associated with the cell wall compartment are expected to participate in growth modulation because cell walls must be altered for cell enlargement to occur.…”