Document Type

Thesis - Open Access

Award Date

2024

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Anne Fennell

Abstract

Grapevine and soybean are two economically important crops, each with unique yet equally crucial physiological processes that profoundly influence their growth and productivity. Grapevine (Vitis sp.), a temperate fruit crop, employs dormancy to withstand winter challenges and can grow in various regions worldwide. Understanding the molecular mechanisms involved in dormancy in Vitis species, is crucial for improving grapevine selection for resilience in northern temperate regions. Dormancy induction is modulated by decreasing photoperiods in some Vitis species, enhancing their ability to prepare for winter stress conditions. Understanding the molecular underpinnings of response to photoperiod will provide potential markers for selecting genotypes that better adapt to cold climates. In grapevine, dormancy development involves two major steps (1) growth cessation and tip abscission in shoots and (2) bud dormancy or inability to resume outward shoot growth. To characterize the molecular pathways and potential regulators of these processes, we (1) characterized the transcriptomic response to photoperiod induced growth cessation using the reference V. vinifera gene models and new V. riparia specific gene models (2) identified grapevine bud miRNA, as potential regulators of gene expression, during short photoperiod dormancy induction. Through comparative analysis using Vitis vinifera and Vitis riparia reference genomes, RNA sequencing on shoot-tips under varying photoperiod induced shoot-tip growth cessation revealed significant differential gene expression and showed unique pathways when the V. riparia gene models were employed, emphasizing a robust autophagic response during growth cessation. This underscores the importance of species-specific genome assemblies in capturing ecologically relevant gene expression changes. We further explored dormancy in grapevine buds by investigating the role of microRNAs in F2 hybrid siblings under controlled photoperiod treatments. Significant changes in miRNA expression associated with dormancy induction were identified, revealing distinct temporal and genotypic differences in miRNA regulation. These findings underscore potential regulation of gene expression and timing of dormancy development in response to reduced photoperiods. Overall, our research increases the understanding of the development and regulation of dormancy in grapevine, providing potential selectable markers for grapevine improvement and sustainability. Soybean’s symbiotic relationship with nitrogen-fixing rhizobia bacteria contributes up to 70% of its nitrogen needs. The significance is the reduced need for expensive and environmentally hazardous chemical nitrogen fertilizers in agriculture. This symbiosis involves two major processes: (1) nodule development where the plant root cells divide to generate a specialized organ that accommodates nitrogen-fixing rhizobia and (2) nitrogen fixation a process that occurs inside the nodules where rhizobia reduce atmospheric nitrogen into ammonia and the two organisms cooperatively produce nitrogenous compounds. To distinguish molecular pathways and regulators associated with these processes, we bioinformatically predicted gene regulatory networks (GRNs), used a global transcriptome dataset derived from nodules produced by an effective nitrogen-fixing and ineffective non-fixing rhizobium strains.

Publisher

South Dakota State University

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Rights Statement

In Copyright