Shankhapal, Aishwarya Rajesh
(2025)
Understanding mesocotyl elongation in rice.
PhD thesis, University of Nottingham.
Abstract
Mesocotyl elongation is a valuable trait for successful germination and establishment of direct-seeded rice (DSR) because it enables seedlings to germinate from deeper sowing depths and produce vigorous early growth in unfavourable field conditions. In this thesis, the systematic genetic and molecular dissection of the mesocotyl elongation trait in Oryza sativa is outlined with a focus on the Cellulose Synthase A (CesA) gene family, and in particular OsCesA3, which is revealed as a promising and novel regulator of the trait. A detailed in-silico screening of the CesA gene family revealed gene structures that were heterogeneous, evolutionarily conserved, and rich in hormone-responsive elements within the promoter regions, especially for gibberellins and auxin—two hormones that are known to cause elongation growth. OsCesA3 was identified as an important candidate gene within the family based on its developmental expression pattern, association with mesocotyl length in a GWAS, and regulatory responsiveness.
Functional determination by overexpression and CRISPR/Cas9-mediated gene editing also support the role of OsCesA3 in controlling mesocotyl elongation. Overexpression lines exhibited increased mesocotyl length and increased cellulose deposition, and gene-edited lines exhibited reduced elongation and abnormal cell wall sugar composition with decreased cellulose and increased hemicellulose. These results suggest OsCesA3 as a crucial regulator of primary cell wall biosynthesis and elongation-specific growth in the mesocotyl. Notably, cross-species complementation in Arabidopsis thaliana rescued the short hypocotyl phenotype of the prc1-1 mutant, confirming functional conservation of CesA3 in monocots and dicots.
The understanding of the mesocotyl elongation process was also facilitated by transcriptomic analysis, revealing differential expression of cell wall modifying enzymes, hormone signalling genes, and novel transcription factors in long and short mesocotyl genotypes. Expansin, XTH, and pectin esterase genes were overexpressed in long mesocotyl lines, and regulatory factors such as ZOS4-14 (C2H2 zinc finger protein), MYB-like, and AP2 domain transcription factors were chief suspects for upstream regulation of elongation pathways. Interaction among gibberellin, auxin, and cytokinin hormone pathways was also evident and suggestive of the coordination and complexity of hormonal regulation of elongation. Together, these findings increase our understanding of the genetic and molecular factors controlling mesocotyl elongation and provide approaches to improve DSR practices.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Eastmond, Peter J.
Kurup, Smita
Bennett, Malcolm J.
Band, Leah R. |
| Keywords: |
Mesocotyl elongation trait; Oryza sativa; Cellulose Synthase A (CesA) gene family; Hormonal regulation; Direct-seeded rice |
| Subjects: |
Q Science > QK Botany |
| Faculties/Schools: |
UK Campuses > Faculty of Science > School of Biosciences |
| Item ID: |
82652 |
| Depositing User: |
Shankhapal, Aishwarya
|
| Date Deposited: |
12 Dec 2025 04:40 |
| Last Modified: |
12 Dec 2025 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/82652 |
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