Plant organellar calcium signalling: an emerging field

Abstract

This review provides a comprehensive overview of the established and emerging roles that organelles play in calcium signalling. The function of calcium as a secondary messenger in signal transduction networks is well documented in all eukaryotic organisms, but so far existing reviews have hardly addressed the role of organelles in calcium signalling, except for the nucleus. Therefore, a brief overview on the main calcium stores in plants-the vacuole, the endoplasmic reticulum, and the apoplast-is provided and knowledge on the regulation of calcium concentrations in different cellular compartments is summarized. The main focus of the review will be the calcium handling properties of chloroplasts, mitochondria, and peroxisomes. Recently, it became clear that these organelles not only undergo calcium regulation themselves, but are able to influence the Ca(2+) signalling pathways of the cytoplasm and the entire cell. Furthermore, the relevance of recent discoveries in the animal field for the regulation of organellar calcium signals will be discussed and conclusions will be drawn regarding potential homologous mechanisms in plant cells. Finally, a short overview on bacterial calcium signalling is included to provide some ideas on the question where this typically eukaryotic signalling mechanism could have originated from during evolution.

Synchrotron-based Techniques Shed Light on Mechanisms of Plant Sensitivity and Tolerance to High Manganese in the Root Environment

“…S7, B and C) showed that these two elements were colocated in the vacuoles (Fig. 3B), thereby ensuring low cytoplasmic concentrations of Ca (Stael et al, 2012) and Mn (Hughes and Williams, 1988;Peiter et al, 2007). This suggests that narrow-leafed lupin is able to translocate Mn(II) from the apoplast for storage in the vacuole, possibly via a Ca transporter (Millaleo et al, 2010), limiting the accumulation of Mn in the cytoplasm and cell wall.…”

“…m-XRF analysis indicated that Ca was located mostly in the vacuoles (Supplemental Fig. S6B), which Stael et al (2012) concluded contain approximately 80 mM Ca compared with only approximately 100 nM in the cytoplasm. The concentration of Mn must be maintained at less than 100 nM in the cytoplasm also (Hughes and Williams, 1988), but in contrast to Ca, there was low Mn in the vacuoles but high in some intervening spaces ( Fig.…”

“…S6B), the spots being interpreted as vacuoles where high Ca accumulates. It is possible to use Ca concentration as an indicator of subcellular distribution given that Ca in the vacuole (1-80 mM) is often 10,000-fold higher than in the cytoplasm (100 nM; Stael et al, 2012). There was a clear difference between Ca and Mn distribution in this region, with no vacuolar Mn evident (Supplemental Fig.…”

Rapid hyperosmotic-induced Ca 2+ responses in Arabidopsis thaliana exhibit sensory potentiation and involvement of plastidial KEA transporters

“…It has recently become evident that plastids represent a significant pool for Ca 2+ release in plants (21,37,38). We measured hyperosmotic-induced Ca 2+ responses in plastidial-localized kea mutant lines.…”

First evidence on phloem transport of nanoscale calcium oxide in groundnut using solution culture technique

“…levels fluctuate and they are in rapid control of membrane-localized Ca 2? pumps and channels located in plasmalemma, vacuoles and endoplasmic reticulum of plants (Stael et al 2011;Ng and Mcainsh 2003;Yang and Poovaiah 2003). Therefore, it is anticipated that due to the small size, high surface area-tovolume ratio and continuum in flux, nanoscale calcium oxide particles could be transported with ease through ionic channels in the plant system and also we imagine that the relatively high electrochemical potential energy of the nanoscale materials also plays an important role in phloem transport of calcium oxide nanoparticles.…”