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Auxin induces exocytosis of acid phosphatase in coleoptiles from Zea Mays
Author(s) -
Pfeiffer Wolfgang
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1996.tb06684.x
Subject(s) - coleoptile , acid phosphatase , extracellular , biochemistry , phosphatase , auxin , biology , chemistry , enzyme , gene
Auxin‐stimulated elongation growth of maize coleoptiles has been suggested to be associated with enhanced exocytotic activity. However, the problem in plants is one of finding a soluble parameter, which can be used as a direct measure of exocytosis (H. D. Blackbourn and N. H. Battey [1993]. Physiol. Plant. 89: 27–32). In yeast, acid phosphatase (EC 3.1.3.2) is used as a marker for secretory activity (E. Harsay and A. Bretscher [1995]. J. Cell Biol. 131: 297–310). Therefore, extracellular acid phosphatase activities in maize tissues were investigated. Coleoptile (7.36 nkat mg ‐1 ) and mesocotyl (8.9) showed higher specific extracellular acid phosphatase activities than primary leaf (6.0), root (4.9) and root tip (2.7). In coleoptiles extracellular acid phosphatase activity was 6.7% of total homogenate activity (mesocotyls 10.6%). Auxin (30 μM IAA) increased the extracellular acid phosphatase activity of coleoptiles (146% of control). This effect was tissue‐specific; extracellular acid phosphatase activity of mesocotyls was not enhanced by IAA. The stimulating effect of auxin on extracellular acid phosphatase activity in coleoptiles was reversed by the protonophore nigericin (0.3 μM). Furthermore, localization of an acid phosphatase activity in Golgi vesicles was shown by co‐migration of the Golgi marker latent IDPase (EC 3.6.1.6) and acid phosphatase activity (65% of total microsomal activity) on isopycnic continuous sucrose density gradients. Tonoplast‐enriched membrane frctions (24% of microsomal acid phosphatase) and plasma membrane‐enriched fractions (11%) contained lower amounts of acid phosphatase. The data presented suggest that acid phosphatase activity is a useful marker for hormone‐induced secretory activity in plant cells.