ISSN:
1432-2048
Keywords:
Auxin-binding protein
;
Glycine max L
;
Guanosine nucleotides
;
Phospholipase A2
;
Signal transduction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The molecular mechanism of membrane-associated reactions induced by auxin was investigated in membranes isolated from cultured cells of soybean (Glycine max L.). Auxins increased the activity of phospholipase A2 in microsomes isolated from suspensioncultured soybean cells. The reaction was measured as the accumulation of radioactive lysophosphatidylcholine hydrolyzed from radioactive phosphatidylcholine in membranes which had been prelabelled with [14-C]choline in vivo. Stimulation by auxin was detectable after 1 min and was auxin-specific in that weak auxins had little effect. Auxin concentrations as low as 2·10−8 M and up to 2·10+3 M α-naphthaleneacetic acid already stimulated the phospholipase A2 activity. Guanosine and adenosine diphosphate at 100 μM, if applied during homogenization of cells, completely abolished the stimulation of phospholipase A2 by auxin and, when applied after homogenization, had no effect. Guanosine and adenosine 5′-O-thiotriphosphate, uridine 5′-diphosphate, and uridine 5′-triphosphate, all at 100 μM, had no effect in either treatment, suggesting that only nucleotides entrapped in the vesicles could exert an effect. The effect of auxin on phospholipase A2 had an optimum at pH 5.5 and was abolished completely by an antibody against the membrane-associated auxin-binding protein from maize coleoptiles, applied after homogenization. This antibody recognized a 22-kDa polypeptide in highly purified plasma membranes from cultured soybean cells. This suggests a receptor function for this auxin-binding protein and a role for a cytosolic nucleotide-binding protein in the activation of phospholipase A2 by auxin. It is concluded that phospholipase A2 has a function in plant signal transduction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00195753
Permalink
