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Calcium‐dependent protein kinase in maize and sorghum induced by polyethylene glycol
Author(s) -
Pestenácz Anikó,
Erdei László
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 - 10.1034/j.1399-3054.1996.970221.x
Subject(s) - abscisic acid , calmodulin , shoot , sorghum , osmotic shock , signal transduction , kinase , enzyme , polyethylene glycol , protein kinase a , peg ratio , phosphorylation , calcium , zea mays , biochemistry , biology , chemistry , botany , agronomy , gene , organic chemistry , finance , economics
Several environmental and hormonal stresses activate signal transduction in plants. Various enzymes are involved in these mechanisms. Studying one of these enzymes, we found osmotically‐induced, calcium‐dependent protein kinases (CDPKs), and hypothesized a connection between osmotic and hormonal signals. CDPKs were investigated in cultivars of relatively drought‐tolerant maize ( Zea mays L.) and drought‐tolerant sorghum ( Sorghum bicolor L.). Plants were grown hydroponically for 11 days and treated with abscisic acid (ABA, 0.1 μ M ) starting from day 5, and with polyethylene glycol 6000 starting from day 8 at 0, 100 and 200 mOsm concentrations. As a function of time, treatments lasted for 0, 15, 30, 60, 120 min and 72 h. For the determination of CDPK activity, the 25000 g supernatant of shoots and roots were used for SDS‐PAGE and autoradiography. An increased CDPK activity was found after 1 h of osmotic stress in sorghum roots and Only low levels of phosphorylation could be measured in maize. Little or no activities were detected in the shoots. The Ca 2+ ‐dependent phosphorylation appeared as 49‐ and 52‐kDa bands. Calmodulin (CaM) added in vitro did not change the enzyme activity but inhibition by a CaM antagonist, trifluoroacetic acid, was significant. We also found that pretreatment with ABA reverted the stress‐induced changes in sorghum roots. We concluded that this CDPK is involved in the early steps of the signal transduction pathway, and is connected with ABA‐induced mechanisms.