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Calcium influxes and mitogen‐activated protein kinase kinase activation mediate ethylene inducing ipomoelin gene expression in sweet potato
Author(s) -
CHEN YUCHI,
LIN HSINHUNG,
JENG SHIHTONG
Publication year - 2008
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2007.01742.x
Subject(s) - egta , cytosol , gene expression , kinase , chemistry , microbiology and biotechnology , biochemistry , calcium , biology , gene , enzyme , organic chemistry
The ipomoelin gene ( IPO ) was identified to be a wound‐inducible gene from Ipomoea batatas , and its expression was stimulated by methyl jasmonate (MeJA) and hydrogen peroxide. IPO protein was also characterized as a defence‐related protein, and it is also a carbohydrate‐binding protein. In this study, the expression of IPO was used as a molecular probe to study the effects of Ca 2+ on the signal transduction of ethylene. A confocal microscope monitored the Ca 2+ within cells, and Northern blotting examined IPO expression. The presence of Ca 2+ channel blocker, including diltiazem, neomycin or ruthenium red, abolished the increase of cytosolic Ca 2+ , and reduced the IPO expression in the cells induced by ethylene. Furthermore, both Ca 2+ influxes and IPO expression stimulated by ethylene were prohibited in the presence of 10 m m ethylene glycol‐ bis (2‐aminoethyl ether)‐ N , N , N ′, N ′‐tetraacetic acid (EGTA). These results indicated that Ca 2+ influxes into the cytosol induced by ethylene are from both apoplast and organelles, and are required for activating IPO expression. However, in the presence of 1 m m EGTA, ethylene can still stimulate IPO expression, but mechanical wounding failed to do it. Therefore, Ca 2+ channels in the plasma membrane induced by ethylene have higher affinity to Ca 2+ than that stimulated by wounding. Moreover, the addition of A23187, an ionophore, raised cytosolic Ca 2+ , but was unable to stimulate IPO expression. These findings showed that IPO induction did not solely depend on Ca 2+ , and Ca 2+ elevation in cytosol is necessary but not sufficient for IPO expression. The application of PD98059, a mitogen‐activated protein kinase kinase (MAPKK) inhibitor, did not prevent Ca 2+ from increasing in the cytosol induced by ethylene, but inhibited the IPO expression stimulated by staurosporine (STA), a protein kinase inhibitor. Conclusively, elevation of cytosolic Ca 2+ by ethylene may stimulate protein phosphatase and MAPKK, which finally activates IPO expression.