Archived
This content is available here for research, reference, and/or recordkeeping.
Author ORCID Identifier
https://orcid.org/0000-0001-5055-195X
Date Available
7-30-2027
Year of Publication
2026
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Agriculture, Food and Environment
Department/School/Program
Plant and Soil Sciences
Faculty
Tomokazu Kawashima
Faculty
Arthur Hunt
Abstract
Land plants have undergone numerous changes which have helped in their successful colonization of the land and innovations in the sexual plant reproduction have played a major role in this process. In angiosperms, plant reproduction involves a complex and intricate process called double fertilization where two immotile sperm cells are transported to the female gametophyte. The two sperm cells fuse with the egg cell and central cell to form the embryo and endosperm. Angiosperms have evolved a unique mechanism where actin filaments (F-actin) control the sperm nuclei movement for the completion of successful double fertilization. In central cell, a unique ACTIN-RELATED PROTEIN 2/3 (ARP2/3) independent Wiskott–Aldrich syndrome protein family verprolin-homologous/suppressor of the cAMP receptor (WAVE/SCAR) pathway had been identified. In our study, with the help of pharmacological and mutants, we found that several key factors such as Rho GTPase of Plants (ROP), WAVE/SCAR and FORMINs are involved in the same genetic pathway controlling F-actin dynamics in the central cell. Whereas MYOSIN works independently of the ROP-WAVE/SCAR-FORMIN pathway for regulating F-actin dynamics in central cell. Our results provide insights into the parallel regulatory mechanisms that control the F-actin dynamics of central cell which are central for sperm nuclear migration and hence completion of successful fertilization.
In Arabidopsis thaliana, early endosperm development follows a unique coenocytic growth phase, characterized by rapid nuclear divisions without cytokinesis, driving seed growth. We found that F-actin forms aster-shaped structures around the nucleus, which are essential for maintaining nuclear organization during coenocytic endosperm development. Manipulation of F-actin dynamics during coenocytic phase alters the final seed size. Specifically, overexpression of ACTIN 8 (ACT8-OX) in the coenocytic endosperm makes bigger seeds while dominant negative form of ACTIN 8 (DN-ACT8) in coenocytic endosperm makes smaller seeds, suggesting that F-actin properties directly influence seed development. Although multiple ACTIN isovariants exist in plants, their isovariant-specific roles in reproductive tissues remain poorly characterized. Through transcriptome analysis, we identified ACTIN10 (ACT10) as highly enriched in the chalazal endosperm (CZE)—a region critical for nutrient transport. Functional analysis revealed that ACT10 polymerizes faster and forms less bundled filaments compared to ACT8. Loss of function mutation of act10 leads to less nuclear deposition into the CZE which can be attributed to the polymerization speed of ACT10. Together, our results highlight distinct, isovariant-specific functions of actin in the developing endosperm. We propose that differential expression and biochemical properties of ACTIN isovariants contribute to the spatial organization and growth potential of seed tissues. These findings uncover a new layer of cytoskeletal regulation during seed development and suggest that manipulating specific ACTIN isovariants could be a strategy to modulate seed size and yield.
Furthermore, to understand the biophysical side of coenocytic endosperm development and its role in determining the final seed size, we combined the molecular and biophysics studies to investigate how altering F-actin dynamics can cause differences in growth and development of the endosperm, ultimately impacting the final seed size. We measured the seed stiffness of young seeds, which positively correlates with the turgor pressure of the coenocytic endosperm, and found significant differences among the control, OX-ACTIN and DN-ACTIN lines. Our results indicate that F-actin dynamics in coenocytic endosperm not only assist in nuclear positioning and movement, but also regulate seed stiffness (the coenocytic endosperm turgor pressure). The connection between F-actin dynamics and turgor pressure offers insights into the unique developmental mechanism of the coenocytic endosperm and presents new opportunities for increasing seed size, a crucial aspect for food security.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2026.378
Archival?
Archival
Recommended Citation
Sharma, Vijyesh, "Molecular and cellular dynamics of fertilization mechanisms and coenocytic endosperm development in Arabidopsis thaliana" (2026). Theses and Dissertations--Plant and Soil Sciences. 211.
https://uknowledge.uky.edu/pss_etds/211
