Strawberry Skin Stops Forming as the Fruit Grows

Jim Crocker
2nd July, 2024

Strawberry Skin Stops Forming as the Fruit Grows

The rapid expansion and ripening of strawberry (Fragaria x ananassa) fruit (a–d) outpace cuticle deposition, causing cuticular mass per unit area to decrease (f) despite a net increase per fruit (e), which results in significant mechanical strain (g).

Image adapted from: Straube et al. / CC BY (Source)

Key Findings

  • The study took place at Leibniz University Hannover and focused on understanding cuticle deposition in rapidly developing strawberry fruits
  • Researchers found that cutin is actively deposited on the inner surface of the strawberry cuticle during fruit development
  • The study revealed that cuticle deposition does not keep pace with the rapid increase in fruit surface area, leading to a thinning cuticle and increased strain
Strawberries, known for their rapid development and thin cuticles, present a unique challenge in maintaining effective barrier properties throughout their growth. Researchers at Leibniz University Hannover aimed to understand the developmental time course of cuticle deposition in strawberry fruit[1]. This study builds on prior knowledge about plant cuticles, their composition, and their role in protecting plants from environmental stresses. The plant cuticle is an extracellular hydrophobic layer that covers the aerial parts of all land plants, providing protection against desiccation and external environmental stresses[2]. It is primarily composed of two major components: cutin, a polymer, and cuticular waxes. Recent advancements have allowed scientists to construct nearly complete biosynthetic pathways for both waxes and cutin, revealing a complex regulatory network controlling cuticle synthesis[2]. The cuticle's role extends beyond acting as a barrier to water loss, influencing various developmental processes and interactions with microbes. A previous study highlighted that the cuticle is the major barrier against uncontrolled water loss from leaves, fruits, and other primary parts of higher plants[3]. It was found that cuticular water permeability is not correlated to the thickness of the cuticle or to wax coverage. Instead, the permeability increases with temperature and can be influenced by organic compounds. The bulk of water diffuses as single molecules across a lipophilic barrier, while a minor fraction travels along polar pores[3]. In the context of fruit development, the pattern of cuticle deposition is crucial in managing strain buildup, which can lead to surface disorders[4]. Evidence indicates that a strain gradient exists within the apple fruit cuticle, with the outer layers being more strained and susceptible to microcracking than the inner layers. This gradient is likely due to the radial deposition of new cutin on the inner surface of the cuticle, leading to a gradient in cuticular age[4]. The study conducted by Leibniz University Hannover aimed to establish the developmental timeline of cuticle deposition in strawberry fruit. Given the rapid development and thin cuticles of strawberries, understanding this process is essential for enhancing their barrier properties throughout growth. Researchers used a method involving the feeding of 13C-labeled oleic acid to developing strawberry fruits through the skin. After a 14-day incorporation period, the fruits were harvested, and the cuticular membranes (CMs) were isolated enzymatically. The CMs were then ablated to varying extents from both the inner and outer surfaces using cold atmospheric pressure plasma (CAPP). Following ablation, the CMs were dewaxed, and the 13C content was determined by mass spectrometry. The results showed that the incorporation of 13C in the cutin fraction was higher than in the wax fraction, indicating active deposition of cutin during fruit development. The 13C content was highest in non-ablated, dewaxed CM and decreased as ablation depth from the inner surface increased. There was no change in 13C content when ablation was carried out from the outer surface. As fruit development proceeded, more 13C label was found towards the middle of the DCM, providing direct evidence that cutin deposition occurs on the inner surface of the cuticle, abutting the epidermal cell wall. This finding aligns with previous research on apple fruit cuticles, which also showed a radial gradient in cuticle age, with the youngest cutin being deposited on the inner surface[4]. The study expands on the understanding of cuticle deposition by demonstrating that similar processes occur in rapidly developing fruits like strawberries, despite their thin cuticles. In summary, the study by Leibniz University Hannover provides valuable insights into the developmental timeline of cuticle deposition in strawberry fruit. By establishing that cutin is deposited on the inner surface of the cuticle, the research highlights the dynamic nature of cuticle development and its importance in maintaining barrier properties throughout fruit growth. This knowledge could inform future strategies to enhance the durability and quality of strawberry fruit, benefiting both producers and consumers.

FruitsBiochemPlant Science

References

Main Study

1) Cuticle deposition ceases during strawberry fruit development

Published 29th June, 2024

https://doi.org/10.1186/s12870-024-05327-7

Related Studies

2) The formation and function of plant cuticles.

https://doi.org/10.1104/pp.113.222737

3) Protecting against water loss: analysis of the barrier properties of plant cuticles.

Journal: Journal of experimental botany, Issue: Vol 52, Issue 363, Oct 2001

4) Direct Evidence for a Radial Gradient in Age of the Apple Fruit Cuticle.

https://doi.org/10.3389/fpls.2021.730837


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