A transcriptome and functional study of shoot branching potential
Year: 2023
Type: dissertation
Abstract: Shoot branching of flowering plants exhibits phenotypic plasticity and variability. This plasticity is determined by the activity of axillary meristems, influenced by endogenous and exogenous signals, such as nutrients and light. In many species, not all buds on the main shoot develop into branches despite favourable growing conditions. In petunia, basal axillary buds typically do not grow out to form branches, while more apical axillary buds are competent to grow. It is likely the regulation of outgrowth between axillary buds at different positions differs, and that additional regulatory elements modulate the outgrowth under different environmental conditions. To test this hypothesis, the genetic regulation of buds was explored using transcriptome analyses of petunia axillary buds at different positions on the main stem, and as plants transition from growth-promoting (high phosphate (P)) to growth-suppressing conditions (low P) and vice versa. There were substantial differences in transcriptome profiles between the basal and more apical axillary buds, reflecting the difference in their growth outcomes. It appeared that the outgrowth of basal axillary buds was actively suppressed and in addition to strigolactones, abscisic acid is likely involved in this growth suppression. Furthermore, comparisons between these data and transcriptome data from other species suggest that the suppression of outgrowth of basal buds was correlated with a limited supply of carbon to these axillary buds. Based on the transcriptome results, 21 candidate genes were identified as their transcript levels were either correlated with promoting or suppressing bud outgrowth. To investigate their roles in branching regulation, the mutant phenotypes of these candidates were studied. Among them, several exhibited altered branching patterns. Further in-depth studies on three specific mutants, namely Arabidopsis scarecrow-like28 and cytokinin oxidases (ckx3 ckx5), and petunia hyoscyamine 6-dioxygenase (h6h), offered new understanding of how these genes may regulate axillary bud outgrowth. Overall, this thesis demonstrates that axillary buds with different developmental potentials exhibit distinct transcriptome profiles and regulatory controls. By identifying candidates from the transcriptome analyses and studying their loss-of-function mutants, I have identified new genes that likely play a role in branching regulation. Future studies will focus on exploring how these genes modulate branching.
Author: Luo, Zhiwei
Language: English
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W7062566708