Uncovering the Molecular Mechanism of Flowering in a Marine Angiosperm, Zostera marina, and Evaluating the Effects of Warming on Flowering Processes
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| Publicado en: | ProQuest Dissertations and Theses (2025) |
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| Acceso en línea: | Citation/Abstract Full Text - PDF |
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| Resumen: | Florigen and antiflorigen genes within the phosphatidylethanolamine-binding protein (PEBP) gene family regulate flowering in angiosperms. In eelgrass (Zostera marina), an estuarine foundation species, flowering and seed production are crucial for population resilience, especially in the face of rising seawater temperatures, more frequent extreme weather events, and anthropogenic disturbances. Yet, the molecular mechanism underpinning flowering remains unknown.In Chapters 1 and 2, we investigate the role of florigen and antiflorigen genes in Zostera marina in the regulation and onset of flowering. We identified thirteen PEPB genes in in Z. marina (ZmaPEBP); ten FT (florigen) homologs, two TFL1 homologs, and one MFT homolog. Among these thirteen ZmaPEBP genes, when over-expressed in Arabidopsis, two genes (ZmaFT2 and ZmaFT4) cause an early flowering phenotype, and two genes (ZmaFT9, and ZmaTFL1a) caused a late flowering phenotype. To gain insight into the function of these four genes in eelgrass, we analyzed gene expression in different plant tissue from adult perennial shoots in either vegetative or flowering reproductive phases at three sites (Willapa Bay, WA USA). ZmaFT2, ZmaFT4, and ZmaTFL1a expression was higher in flowering rhizome and shoot tissues, while ZmaFT9 was solely expressed in leaves of vegetative shoots. We also analyzed gene expression in annual eelgrass shoots over the growth season from three sites across two bays (Willapa Bay, WA and Yaquina Bay, OR USA). ZmaFT2, ZmaFT4, expression increased at the time of flowering and ZmaTFL1a expression increased after flowering onset occurred. ZmaFT9 expression was high in leaves of early vegetative seedlings but decreased shortly before flowering onset. Our results suggest that ZmaFT2 and ZmaFT4 may promote flowering and ZmaTFL1a may be involved with flowering-related developmental processes, such as shoot architecture, while ZmaFT9 may inhibit flowering in eelgrass.In Chapter 3, using Z. marina, we applied a common garden approach to experimentally test how flowering and its underlying molecular mechanisms responded to elevated water temperature (+3°C). We focused on developmental and reproductive traits paired with ZmaPEBP gene expression to gain insight to the molecular mechanism underpinning differences in flowering responses. We compared annual shoots from two source populations (Willapa Bay and Padilla Bay, WA, USA) to understand natural variation not only in morphological and reproductive traits, but also in ZmaPEBP gene expression governing flowering onset. At the individual and population levels, annual seedlings in the +3°C heated treatment produced more spathes and accelerated development of inflorescences so seeds dispersed sooner. Also, seedlings from Padilla Bay flowered at greater rates and earlier than Willapa Bay, and these differences were exaggerated by the +3°C heated treatment. Two predicted floral activators, ZmaFT2 and ZmaFT4 had increasing expression throughout the summer regardless of population and showed no response to the temperature treatment. ZmaFT9 expression, a predicted repressor of flowering onset, was expressed at lower levels in the shoots grown in the +3°C heated treatment, and even more so in the Padilla Bay population which flowered earlier than the Willapa Bay population. ZmaTFL1a, a gene predicted to be involved with downstream flowering processes, showed no significant response to the temperature treatment. These results highlight the contribution of ZmaFT9 expression to the temperature-based response of timing of flowering onset. Elevated seawater temperature impacted flowering timing and spathe production, with potential consequences for seed yield and meadow resilience.Combined, these studies support the key role of antiflorigen (ZmaFT9) in the molecular control of flowering in Z. marina, not only as the main determinant of flowering onset, but also as an integrator of temperature into the flowering response. Florigen genes that contribute to the activation of flowering (ZmaFT2 and ZmaFT4) and genes that are responsible for flowering related developmental processes (ZmaTFL1a) are also important components of the flowering mechanism. |
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| ISBN: | 9798288833960 |
| Fuente: | ProQuest Dissertations & Theses Global |