Cytosolic and Nucleosolic Calcium Signaling in Response to Osmotic and Salt Stresses Are Independent of Each Other in Roots of Arabidopsis Seedlings

Abstract

Calcium acts as a universal second messenger in both developmental processes and responses to environmental stresses. Previous research has shown that a number of stimuli can induce [Ca2+] increases in both the cytoplasm and nucleus in plants. However, the relationship between cytosolic and nucleosolic calcium signaling remains obscure. Here, we generated transgenic plants containing a fusion protein, comprising rat parvalbumin (PV) with either a nuclear export sequence (PV-NES) or a nuclear localization sequence (NLS-PV), to selectively buffer the cytosolic or nucleosolic calcium. Firstly, we found that the osmotic stress-induced cytosolic [Ca2+] increase (OICIcyt) and the salt stress-induced cytosolic [Ca2+] increase (SICIcyt) were impaired in the PV-NES lines compared with the Arabidopsis wildtype (WT). Similarly, the osmotic stress-induced nucleosolic [Ca2+] increase (OICInuc) and salt stress-induced nucleosolic [Ca2+] increase (SICInuc) were also disrupted in the NLS-PV lines. These results indicate that PV can effectively buffer the increase of [Ca2+] in response to various stimuli in Arabidopsis. However, the OICIcyt and SICIcyt in the NLS-PV plants were similar to those in the WT, and the OICInuc and SICInuc in the PV-NES plants were also same as those in the WT, suggesting that the cytosolic and nucleosolic calcium dynamics are mutually independent. Furthermore, we found that osmotic stress- and salt stress-inhibited root growth was reduced dramatically in the PV-NES and NLS-PV lines, while the osmotic stress-induced increase of the lateral root primordia was higher in the PV-NES plants than either the WT or NLS-PV plants. In addition, several stress-responsive genes, namely CML37, DREB2A, MYB2, RD29A, and RD29B, displayed diverse expression patterns in response to osmotic and salt stress in the PV-NES and NLS-PV lines when compared with the WT. Together, these results imply that the cytosolic and nucleosolic calcium signaling coexist to play the pivotal roles in the growth and development of plants and their responses to environment stresses.

Dual Color Sensors for Simultaneous Analysis of Calcium Signal Dynamics in the Nuclear and Cytoplasmic Compartments of Plant Cells

“…Moreover, The NaCl-induced nucleoplasmic Ca 2+ signal had a higher amplitude than the cytoplasmic Ca 2+ signal, which contrasts with the cold-induced Ca 2+ signal, smaller in amplitude. These results support the induction of nuclear Ca 2+ signals independently of the cytoplasmic Ca 2+ release, as implied by a recent study regarding the NaCl-induced cytoplasmic/nuclear Ca 2+ dynamics (Huang et al, 2017 ). Alternatively, the cytoplasmic Ca 2+ release might be contributing to the generation of the nuclear Ca 2+ signal either by diffusion or by triggering a Ca 2+ -induced Ca 2+ release mechanism at the nuclear envelope.…”

The SOS2-SCaBP8 Complex Generates and Fine-Tunes an AtANN4-Dependent Calcium Signature under Salt Stress

“…The results ( Figure 1G; Videos S1, S2, and S3) showed that salt stress triggered a rapid increase in [Ca 2+ ] cyt as indicated by changes in the FRET signals of YC3.6 in the root cells of wild-type YC3.6 plants. The maximal changes in FRET signals (DE app /E apprest ) of YC3.6 in the wild-type nearly reached 0.2, similar to previous studies (Huang et al, 2017). However, the maximal changes of YC3.6 signals almost reached 0.5-0.6 in sos2 and scabp8 mutants, indicating a significantly greater increase in [Ca 2+ ] cyt (Figures 1H and 1I).…”

Pharmacological Strategies for Manipulating Plant Ca2+ Signalling

“…It is also used for the calibration of fluorescent Ca 2+ indicators in animal cells [ 138 ]. As an alternative to the chemical Ca 2+ buffers, one could also employ Ca 2+ binding proteins, such as parvalbumin to locally buffer cytoplasmic Ca 2+ signals [ 292 ]. In non-plant systems, optogenetic modulation of light-gated cation channels allows for very precise modulation of Ca 2+ entry [ 293 ].…”