Identification of Hypo-Osmosensors that Control Calcium Spiking during Pollen Germination in Plants

Core Concepts

Hypo-osmosensitive calcium-permeable channels OSCA2.1 and OSCA2.2 convert extracellular water status into calcium spiking, which is essential for pollen germination in plants.

Abstract

The content describes the identification and characterization of hypo-osmosensors that control calcium spiking during pollen germination in plants. The key points are:

Higher plants have evolved mechanisms to monitor water availability and respond to rehydration after dehydration. However, the molecular basis of this osmosensing process was unknown.

The authors developed a functional expression screen in E. coli to identify hypo-osmosensitive channels and found that OSCA2.1, a member of the OSCA protein family, functions as a hypo-osmosensitive calcium-permeable channel.

Further analysis showed that OSCA2.1 and its homolog OSCA2.2 are required for pollen germination and hypo-osmolarity-induced calcium spiking in Arabidopsis.

The OSCA2.1 and OSCA2.2 channels convert extracellular water status into calcium spiking, which is the second messenger for tracking rehydration in plants.

This study provides important insights into how plants sense and respond to changes in water availability during the critical process of pollen germination.

Stats

Pollen germination was impaired in the osca2.1/osca2.2 double-knockout mutant.
Decreasing osmolarity of the medium enhanced pollen calcium oscillations, which were mediated by OSCA2.1 and OSCA2.2.

Quotes

"OSCA2.1 and OSCA2.2 function as hypo-osmosensitive Ca2+-permeable channels in planta and in HEK293 cells."
"OSCA2.1 and OSCA2.2 convert extracellular water status into Ca2+ spiking in pollen and may serve as essential hypo-osmosensors for tracking rehydration in plants."

Key Insights Distilled From

Osmosensor-mediated control of Ca2+ spiking in pollen germination - Nature

by Songyu Pei,Q... at www.nature.com 05-22-2024

https://www.nature.com/articles/s41586-024-07445-6

Deeper Inquiries

How do the OSCA2.1 and OSCA2.2 channels specifically sense changes in extracellular osmolarity and transduce this signal into calcium spiking?

OSCA2.1 and OSCA2.2 channels act as hypo-osmosensors in plants, detecting changes in extracellular osmolarity. These channels are members of the OSCA family of proteins and are hyperosmolarity-gated calcium-permeable channels. When the osmolarity of the medium decreases, these channels are activated, allowing the influx of calcium ions into the cell. This influx of calcium ions triggers calcium spiking, which serves as the second messenger for water status in the cell. Therefore, OSCA2.1 and OSCA2.2 directly convert the extracellular water status into calcium spiking, enabling plants to sense and respond to changes in osmolarity during rehydration.

What other cellular processes or developmental stages in plants might be regulated by OSCA-mediated osmosensing and calcium signaling?

Apart from pollen germination, OSCA-mediated osmosensing and calcium signaling could potentially regulate various other cellular processes and developmental stages in plants. For instance, OSCA channels may play a role in seed germination, root growth, stomatal movement, and responses to environmental stresses such as drought and salinity. Calcium signaling is known to be involved in numerous plant processes, including cell division, cell elongation, hormone signaling, and defense responses. Therefore, OSCA-mediated osmosensing and calcium signaling could have broad implications for plant growth, development, and stress responses beyond pollen germination.

Given the importance of pollen germination for plant reproduction, could modulating OSCA-mediated osmosensing be a potential target for agricultural applications to improve crop yields?

Modulating OSCA-mediated osmosensing could indeed be a promising target for agricultural applications aimed at improving crop yields. Pollen germination is a crucial step in plant reproduction, directly impacting seed set and crop productivity. By manipulating OSCA channels or their downstream signaling pathways, it may be possible to enhance pollen germination efficiency, leading to increased fertilization rates and ultimately higher crop yields. Additionally, improving the plant's ability to sense and respond to changes in osmolarity through OSCA-mediated signaling could help crops better withstand water stress conditions, such as drought, thereby improving their resilience and productivity in challenging environments. Therefore, targeting OSCA-mediated osmosensing holds potential for optimizing plant reproductive success and overall agricultural productivity.