Stomatal closure induced by phytosphingosine-1-phosphate and sphingosine-1-phosphate depends on nitric oxide and pH of guard cells in Pisum sativum
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Phyto-S1P and S1P induced stomatal closure in epidermis of pea ( Pisum sativum ) by raising the levels of NO and pH in guard cells.
Phosphosphingolipids, such as phytosphingosine-1-phosphate (phyto-S1P) and sphingosine-1-phosphate (S1P), are important signaling components during drought stress. The biosynthesis of phyto-S1P or S1P is mediated by sphingosine kinases (SPHKs). Although phyto-S1P and S1P are known to be signaling components in higher plants, their ability to induce stomatal closure has been ambiguous. We evaluated in detail the effects of phyto-S1P, S1P and SPHK inhibitors on signaling events leading to stomatal closure in the epidermis of Pisum sativum. Phyto-S1P or S1P induced stomatal closure, along with a marked rise in nitric oxide (NO) and cytoplasmic pH of guard cells, as in case of ABA. Two SPHK inhibitors, DL-threo dihydrosphingosine and N’,N’-dimethylsphingosine, restricted ABA-induced stomatal closure and prevented the increase of NO or pH by ABA. Modulators of NO or pH impaired both stomatal closure and increase in NO or pH by phyto-S1P/S1P. The stomatal closure by phyto-S1P/S1P was mediated by phospholipase D and phosphatidic acid (PA). When present, PA elevated the levels of pH, but not NO of guard cells. Our results demonstrate that stomatal closure induced by phyto-S1P and S1P depends on rise in pH as well as NO of guard cells. A scheme of signaling events initiated by phyto-S1P/S1P, and converging to cause stomatal closure, is proposed.
KeywordsAbscisic acid LCB signaling Pea Phosphosphingolipids Sphingosine kinase Stomata
- DL-threo DHS
Long chain base
Long chain base phosphate
Slow anion channel
This work was supported by grants (to ASR) from the Department of Biotechnology (No. BT/PR9227/PBD/16/748/2007), Council of Scientific and Industrial Research (CSIR, No. 38(1195)/08/EMR-II), JC Bose Fellow of Department of Science and Technology (No. SR/S2/JCB-06/2006), and Department of Science and Technology-Japanese Society for Promotion of Science (No. DST/INT/JSPS/P-121/10) project (to ASR & KK). MRP, PR, VA, and SA were all supported by Research Fellowships from CSIR/UGC, New Delhi, India. The facilities in our Department and School were supported by grants from DST-FIST, UGC-SAP-CAS and DBT-CREBB, all from New Delhi, India. We thank Ms Nalini, Technical Assistant, Central Instrumentation Laboratory, for her help in using the confocal microscope.
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Conflict of interest
The authors have no conflicts of interest to declare.
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