Dark-Stimulated Calcium Ion Fluxes in the Chloroplast Stroma and Cytosol
AUTOR(ES)
Sai, Jiqing
FONTE
American Society of Plant Biologists
RESUMO
Using transgenic Nicotiana plumbaginifolia seedlings in which the calcium reporter aequorin is targeted to the chloroplast stroma, we found that darkness stimulates a considerable flux of Ca2+ into the stroma. This Ca2+ flux did not occur immediately after the light-to-dark transition but began ∼5 min after lights off and increased to a peak at ∼20 to 30 min after the onset of darkness. Imaging of aequorin emission confirmed that the dark-stimulated luminescence emanated from chloroplast-containing tissues of the seedling. The magnitude of the Ca2+ flux was proportional to the duration of light exposure (24 to 120 h) before lights off; the longer the duration of light exposure, the larger the dark-stimulated Ca2+ flux. On the other hand, the magnitude of the dark-stimulated Ca2+ flux did not appear to vary as a function of circadian time. When seedlings were maintained on a 24-h light/dark cycle, there was a stromal Ca2+ burst after lights off every day. Moreover, the waveform of the Ca2+ spike was different during long-day versus short-day light/dark cycles. The dark-stimulated Ca2+ flux into the chloroplastidic stroma appeared to affect transient changes in cytosolic Ca2+ levels. DCMU, an inhibitor of photosynthetic electron transport, caused a significant increase in stromal Ca2+ levels in the light but did not affect the magnitude of the dark-stimulated Ca2+ flux. This robust Ca2+ flux likely plays regulatory roles in the sensing of both light/dark transitions and photoperiod.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=150780Documentos Relacionados
- Roles of Extensibility and Turgor in Gibberellin- and Dark-stimulated Growth 1
- Correlation between Ion Fluxes and Ion-stimulated Adenosine Triphosphatase Activity of Plant Roots 1
- Differential Ion Accumulation and Ion Fluxes in the Mesophyll and Epidermis of Barley1
- Elicitor-stimulated ion fluxes and O2− from the oxidative burst are essential components in triggering defense gene activation and phytoalexin synthesis in parsley
- Ion Fluxes and Phytochrome Protons in Mung Bean Hypocotyl Segments: I. Fluxes of Potassium 1