Journal Article

ABA activation of an MBP kinase in <i>Pisum sativum</i> epidermal peels correlates with stomatal responses to ABA

Edward C. Burnett, Radhika Desikan, Rosita C. Moser and Steven J. Neill

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 51, issue 343, pages 197-205
Published in print February 2000 | ISSN: 0022-0957
Published online February 2000 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jexbot/51.343.197
ABA activation of an MBP kinase in Pisum sativum epidermal peels correlates with stomatal responses to ABA

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In‐gel protein kinase assays using myelin basic protein (MBP) as substrate have been used to demonstrate that abscisic acid (ABA) activates an MBP kinase (AMBP kinase) in epidermal peels prepared from leaves of the Argenteum mutant of pea, Pisum sativum L. AMBP kinase has the characteristics of a mitogen‐activated protein kinase (MAPK): it utilizes MBP preferentially as an artificial substrate, it is rapidly and transiently activated, it is of the appropriate size (molecular weight c. 45 kDa), requires tyrosine phosphorylation for activity and is tyrosine phosphorylated upon activation. Reverse transcription‐PCR was used to generate a previously‐cloned MAPK from guard cells, epidermis and mesophyll and immunoblotting using an antibody raised against a mammalian MAPK detected MAPK‐related proteins, including one of 45 kDa, in epidermal peels, mesophyll and guard cells. Inhibition of AMBP kinase activation by PD98059, a specific inhibitor of MAPK kinase, and thus MAPK activation, correlated with PD98059‐inhibition of ABA‐induced stomatal closure and dehydrin gene expression, suggesting that ABA effects in pea epidermal peels require MAPK activation. AMBP kinase was not activated by ABA in guard cells isolated by enzyme treatment. However, a protein kinase of c. 43 kDa was activated by ABA in isolated guard cells, but not in mesophyll or epidermal tissue.

Keywords: Abscisic acid; ABA; guard cells; mitogen activated protein kinases, MAPKs; PD98059; tyrosine phosphorylation.; ABA, abscisic acid; DMSO, dimethylsulphoxide; ERK extracellular signal‐regulated protein kinase; MAPK, mitogen‐activated protein kinase; MAPKK, MAPK kinase; MBP kinase, myelin basic protein kinase; membrane intrinsic protein; RT‐PCR, reverse transcription‐polymerase chain reaction

Journal Article.  5890 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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