AI Article Synopsis
- Calcium acts as a crucial signaling molecule in all eukaryotic cells, but how it creates specific signals is still not fully understood.
- In flowering plants, calcium oscillations play a vital role in pollen tube growth and fertilization, and researchers identified key proteins (CNGC channels and calmodulin 2) that function together as a molecular switch to regulate calcium levels.
- Low calcium activates the CNGC channels to increase cytosolic calcium, but once calcium binds to calmodulin 2, it causes the channels to close, demonstrating an auto-regulatory feedback loop that helps manage calcium levels during pollen tube development.
Article Abstract
Calcium is a universal signal in all eukaryotes, but the mechanism for encoding calcium signatures remains largely unknown. Calcium oscillations control pollen tube growth and fertilization in flowering plants, serving as a model for dissecting the molecular machines that mediate calcium fluctuations. We report that pollen-tube-specific cyclic nucleotide-gated channels (CNGC18, CNGC8, and CNGC7) together with calmodulin 2 (CaM2) constitute a molecular switch that either opens or closes the calcium channel depending on cellular calcium levels. Under low calcium, calcium-free calmodulin 2 (Apo-CaM2) interacts with CNGC18-CNGC8 complex, leading to activation of the influx channel and consequently increasing cytosolic calcium levels. Calcium-bound CaM2 dissociates from CNGC18/8 heterotetramer, closing the channel and initiating a downturn of cellular calcium levels. We further reconstituted the calcium oscillator in HEK293 cells, supporting the model that Ca-CaM-dependent regulation of CNGC channel activity provides an auto-regulatory feedback mechanism for calcium oscillations during pollen tube growth.
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| http://dx.doi.org/10.1016/j.devcel.2018.12.025 | DOI Listing |
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