Plant volatiles regulate the activities of Ca2+ -permeable channels and promote cytoplasmic calcium transients in Arabidopsis leaf cells.
A variety of plant species emit volatile compounds in response to mechanical stresses such as herbivore attack. Although these volatile compounds promote gene expression leading to anti-herbivore responses, the underlying transduction mechanisms are largely unknown. While indirect evidence suggests that the cytoplasmic free Ca(2+) concentration ([Ca(2+)](c)) plays a crucial role in the volatile-sensing mechanisms in plants, these roles have not been directly demonstrated. In the present study, we used Arabidopsis leaves expressing apoaequorin, a Ca(2+)-sensitive luminescent protein, in combination with a luminometer, to monitor [Ca(2+)](c) transients that occur in response to a variety of volatile compounds and to characterized the pharmacological properties of the increase in [Ca(2+)](c). When leaves were exposed to volatiles, [Ca(2+)](c) was transiently raised. The [Ca(2+)](c) increases induced by acyclic compounds were disrupted by Ruthenium Red, a potential plasma-membrane and endo-membrane Ca(2+)-permeable channel inhibitor, but not by 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA), an extracellular Ca(2+)-chelator, suggesting that acyclic compounds promote Ca(2+)-release from intracellular stores. On the other hand, the electrophilic compound (E)-2-hexenal promoted Ca(2+)-influx via ROS production by natural oxidation at the aquarius phase. In a gpa1-2 mutant lacking a canonical Galpha subunit, the [Ca(2+)](c) transients induced by all tested volatiles were not attenuated, suggesting that G-protein coupled receptors are not involved in the volatile-induced [Ca(2+)](c) transients in Arabidopsis leaves.
Asai
Naoko
N
Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation, Kawaguchi, Saitama, Japan.
Nishioka
Takaaki
T
Takabayashi
Junji
J
Furuichi
Takuya
T
D000331:Aequorin / Q000378:metabolism; D001059:Apoproteins / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018515:Plant Leaves / Q000166:cytology* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013481:Superoxides / Q000378:metabolism; D055549:Volatile Organic Compounds / Q000378:metabolism*
D001059:Apoproteins; D029681:Arabidopsis Proteins; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011994:Recombinant Proteins; D055549:Volatile Organic Compounds; C060014:apoaequorin; D013481:Superoxides; D000331:Aequorin; D002118:Calcium