How Calcium and Cell Walls Affect Pollen Health in Peonies After Freezing

Jenn Hoskins
17th September, 2024

How Calcium and Cell Walls Affect Pollen Health in Peonies After Freezing

Image Source: Natural Science News, 2024

Key Findings

  • The study by Beijing Forestry University examined pollen viability after cryopreservation in four cultivars of Paeonia lactiflora
  • Increased Ca2+-ATPase activity and higher cytoplasmic Ca2+ levels were observed in all cultivars post-cryopreservation
  • Pollen viability was negatively correlated with cytoplasmic Ca2+ content and positively correlated with Ca2+-ATPase activity and calmodulin (CaM) content
Cryopreservation is a crucial technique for preserving the genetic material of plants, ensuring biodiversity and enabling the exchange of germplasm resources. However, the viability of pollen post-cryopreservation can vary significantly among different cultivars. A recent study conducted by Beijing Forestry University has investigated the factors influencing pollen viability after cryopreservation in four cultivars of Paeonia lactiflora, focusing on the role of calcium ions (Ca2+) and cell wall deposition[1]. The study found that the activity of Ca2+-ATPase and the levels of cytoplasmic Ca2+ increased in all four cultivars after cryopreservation. Ca2+-ATPase is an enzyme that helps regulate calcium levels within cells by pumping Ca2+ out of the cytoplasm, thereby playing a crucial role in maintaining cellular calcium homeostasis. The content of calmodulin (CaM), a protein that binds calcium and helps mediate various cellular processes, varied among the cultivars. The research showed a significant negative correlation between fresh pollen viability and cytoplasmic Ca2+ content, and a positive correlation with Ca2+-ATPase activity. Post-cryopreservation, pollen viability was negatively correlated with cytoplasmic Ca2+ content and positively correlated with CaM content. One cultivar, 'Zi Feng Chao Yang' (ZFCY), which exhibited increased viability after cryopreservation, had significantly higher levels of low-temperature tolerance-related phospholipids and proteins in its pollen cell wall compared to the other cultivars. Additionally, all cultivars maintained a clear Ca2+ gradient at the tips of pollen tubes after cryopreservation, and did not show significant callose accumulation. Callose is a polysaccharide that can deposit in cell walls and is often associated with stress responses in plants. These findings align with previous research on the role of calcium in plant stress responses. For instance, transient elevations in cytosolic calcium are a common response to various stress factors, creating unique calcium "signatures" that are decoded by cellular signaling networks[2]. The current study’s findings on Ca2+-ATPase activity and cytoplasmic Ca2+ levels further emphasize the importance of calcium regulation in maintaining pollen viability under stress conditions such as cryopreservation. Moreover, the study's insights into cell wall dynamics resonate with earlier research on pollen tube growth. The apical wall of growing pollen tubes must balance strength to withstand internal pressure and plasticity to allow growth, a process regulated by pectins and the enzyme pectin methylesterase (PME)[3]. The observed differences in cell wall composition among the Paeonia lactiflora cultivars after cryopreservation suggest that similar mechanisms may be at play in determining pollen viability. Interestingly, the study also found that the Ca2+ gradient and callose at the tips of pollen tubes were not responsible for preventing pollen tube growth post-cryopreservation. This finding contrasts with previous observations where callose deposition and calcium gradients were crucial for maintaining pollen tube integrity and growth under stress conditions[4]. This discrepancy highlights the complexity of plant stress responses and the need for further research to fully understand the underlying mechanisms. In conclusion, the study by Beijing Forestry University provides valuable insights into the factors influencing pollen viability after cryopreservation in Paeonia lactiflora. By highlighting the roles of Ca2+ signaling and cell wall composition, the research offers a deeper understanding of how different cultivars respond to cryopreservation, potentially guiding future efforts in plant germplasm preservation.

GeneticsBiochemPlant Science

References

Main Study

1) Effects of calcium ions and cell wall deposition on the pollen viability of Paeonia lactiflora after cryopreservation.

Published 15th September, 2024

https://doi.org/10.1007/s00425-024-04530-y

Related Studies

2) Calcium efflux systems in stress signaling and adaptation in plants.

https://doi.org/10.3389/fpls.2011.00085

3) Pectin methylesterase, a regulator of pollen tube growth.

Journal: Plant physiology, Issue: Vol 138, Issue 3, Jul 2005

4) Treatment with spermidine alleviates the effects of concomitantly applied cold stress by modulating Ca2+, pH and ROS homeostasis, actin filament organization and cell wall deposition in pollen tubes of Camellia sinensis.

https://doi.org/10.1016/j.plaphy.2020.10.008


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