Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Either hypoxia, which stimulates ethylene biosynthesis, or temporary N starvation, which depresses ethylene production, leads to formation of aerenchyma in maize (Zea mays L.) adventitious roots by extensive lysis of cortical cells. We studied the activity of enzymes closely involved in either ethylene formation (1-amino-cyclopropane-1-carboxylic acid synthase [ACC synthase]) or cell-wall dissolution (cellulase). Activity of ACC synthase was stimulated in the apical zone of intact roots by hypoxia, but not by anoxia or N starvation. However, N starvation, as well as hypoxia, did enhance cellulase activity in the apical zone, but not in the older zones of the same roots. Cellulase activity did not increase during hypoxia or N starvation in the presence of aminoethoxyvinylglycine, an inhibitor of ACC synthase, but this inhibition of cellulase induction was reversed during simultaneous exposure to exogenous ethylene. Together these results indicate both the role of ethylene in signaling cell lysis in response to two distinct environmental factors and the significance of hypoxia rather than anoxia in stimulation of ethylene biosynthesis in maize roots.
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PMID:Induction of Enzymes Associated with Lysigenous Aerenchyma Formation in Roots of Zea mays during Hypoxia or Nitrogen Starvation. 1223 49

Plants of Zea mays L. cv TX5855 were grown in a complete, well oxygenated nutrient solution then subjected to nutrient starvation by omitting either nitrate and ammonium or phosphate from the solution. These treatments induced the formation of aerenchyma close to the apex of the adventitious roots that subsequently emerged from the base of the shoot, a response similar to that shown earlier to be induced by hypoxia. Compared with control plants supplied with all nutrients throughout, N- or P-starvation consistently depressed the rates of ethylene release by excised, 25 mm apical segments of adventitious roots. Some enzymes and substrates of the ethylene biosynthetic pathway were examined. The content of 1-amino cyclopropane-1-carboxylic acid (ACC) paralleled the differences in ethylene production rates, being depressed by N or P deficiency, while malonyl-ACC showed a similar trend. Activity of ACC synthase and of ethylene forming enzyme (g(-1) fresh weight) was also greater in control roots than in nutrient starved ones. These results indicate that much of the ethylene biosynthetic pathway is slowed under conditions of N- or P-starvation. Thus, by contrast to the effects of hypoxia, the induction of aerenchyma in roots of Zea mays by nutrient starvation is not related to an enhanced biosynthesis and/or accumulation of ethylene in the root tips.
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PMID:Decreased Ethylene Biosynthesis, and Induction of Aerenchyma, by Nitrogen- or Phosphate-Starvation in Adventitious Roots of Zea mays L. 1666 8