Comparative analysis of small RNAs and transcriptomic data during the floral transition in Brassica rapa

Magilin, Aileen (2026) Comparative analysis of small RNAs and transcriptomic data during the floral transition in Brassica rapa. Doctoral thesis, University of East Anglia.

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Abstract

Rapid-cycling Brassica crops transition from vegetative to reproductive growth without requiring vernalization. Two cultivars of rapid-cycling B. rapa differ markedly in flowering time; Sarisha-14, a commercial cultivar, flowers almost two weeks earlier than the lab cultivar R-o-18. These contrasting phenotypes provide a unique opportunity to understand how rapid-cycling cultivars regulate flowering time, particularly for Sarisha-14’s precocious flowering.

This thesis tests the hypothesis that the quantitative ratio of two broadly conserved microRNAs, miR156 and miR172, dictate the timing of the vegetative-to-floral transition. To investigate this, I profiled miRNA abundance in the shoot apical meristem across development in both cultivars, and performed bulked segregant analysis (BSA) to identify gene alleles from Sarisha-14 linked to its early flowering phenotype.

My findings reveal that the abundance dynamics of miR156 and miR172 confirm their conserved role in controlling the floral transition. A potential flowering regulatory model emerges, where the miR156/miR172 abundance ratio of log10 value of 1.1 marks the floral transition in both cultivars, and is aligned with Sarisha-14’s earlier shift in flowering time. Additional candidate flowering miRNAs also showed cultivar-specific temporal abundance dynamics. The BSA identified several B. rapa flowering gene orthologues linked to early flowering, especially a disruptive allele of TERMINAL FLOWER 1 (TFL1), a floral repressor, which may contribute to Sarisha-14’s accelerated flowering.

This is the first study to profile microRNA abundance in B. rapa from seedling to floral bud emergence. The findings highlight regulatory mechanisms of flowering time and provide potential targets for breeding crops with shorter reproductive cycles and improved environmental resilience.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	08 Apr 2026 13:40
Last Modified:	08 Apr 2026 13:40
URI:	https://ueaeprints.uea.ac.uk/id/eprint/102711
DOI:

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