How EXPANSIN15 Affects Flower and Fruit Growth

Greg Howard
30th January, 2024

How EXPANSIN15 Affects Flower and Fruit Growth

Without the gene EXPA15, Arabidopsis flower petals become narrow (D) and their surface cells flatten and elongate (F, H) instead of forming their typical conical shape (E, G).

Image adapted from: Bernal-Gallardo et al. / CC BY (Source)
Plant development relies on cells growing and expanding, a process crucial for forming the shapes and sizes of flowers and fruits. Researchers at CINVESTAV-IPN have been investigating the role of a specific gene, EXPANSIN15 (EXPA15), in this process[1]. EXPANSIN genes generally work by loosening the connections between plant cell wall components, allowing cells to expand. This study aimed to understand how EXPA15 contributes to the development of petals, the gynoecium (the female part of the flower), and fruits. The study began by examining what happens when EXPA15 isn’t functioning correctly. By analysing mutant plants – plants with a defective EXPA15 gene – researchers found that EXPA15 plays a role in determining the shape and size of petals. These mutant plants had altered petal cell shapes and a different number of cells, indicating that EXPA15 influences both cell morphology and cell division. Similarly, EXPA15 was found to affect fruit size, again by influencing both cell size and the number of cells within the fruit. Perhaps the most interesting finding was EXPA15’s role in the gynoecium. Specifically, it promotes the fusion of tissues in the medial region of the gynoecium. This fusion is important for the proper formation of the structure that ultimately becomes the fruit. This finding builds on earlier work that identified several genes crucial for gynoecium development, including CRABS CLAW, SPATULA, and AGAMOUS[2]. These genes were shown to be necessary for different aspects of carpel (the individual units of the gynoecium) development, with SPATULA being particularly important for the growth of certain tissues. The current study revealed that EXPA15 doesn’t work in isolation. It interacts genetically with SPATULA and another gene called FRUITFULL (FUL). This means that the effects of EXPA15 are modified when SPATULA or FUL are also altered. These interactions were observed in the gynoecium, affecting the fusion of medial tissues and the development of the style and stigma (the pollen-receiving part of the gynoecium), and also in fruit development. This suggests a complex regulatory network where these genes work together to control floral and fruit development. Previous research highlighted the importance of cell wall remodelling during organ growth, linking changes in the arrangement of internal cell structures (microtubules) to alterations in cell wall properties[3]. The current study adds to this understanding by identifying EXPA15 as a key player in the cell wall loosening process, which is essential for cell expansion and, consequently, organ development. Furthermore, the role of SPATULA in establishing symmetry within the developing style has been previously demonstrated, involving hormonal signalling pathways[4]. The discovery of a genetic interaction between SPATULA and EXPA15 suggests that EXPA15 may contribute to this symmetry establishment process by influencing cell expansion and tissue fusion, potentially impacting auxin distribution and hormonal signalling. The findings from this research demonstrate the importance of EXPANSIN genes in floral and fruit development, and highlight the complex interplay between different genes in controlling these processes. The genetic interactions identified provide valuable insights into the regulatory networks governing plant development, and could potentially be used to improve crop yields by manipulating these genes.

GeneticsBiochemPlant Science

References

Main Study

1) EXPANSIN15 is involved in flower and fruit development in Arabidopsis.

Published 29th January, 2024

https://doi.org/10.1007/s00497-023-00493-4

Related Studies

2) CRABS CLAW and SPATULA, two Arabidopsis genes that control carpel development in parallel with AGAMOUS.

Journal: Development (Cambridge, England), Issue: Vol 126, Issue 11, Jun 1999

3) Transcriptional induction of cell wall remodelling genes is coupled to microtubule-driven growth isotropy at the shoot apex in Arabidopsis.

https://doi.org/10.1242/dev.162255

4) Coordination of biradial-to-radial symmetry and tissue polarity by HD-ZIP II proteins.

https://doi.org/10.1038/s41467-021-24550-6


Related Articles

An unhandled error has occurred. Reload 🗙