Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

Spring 2021

Thesis Director

Yordan S. Yordanov

Thesis Committee Member

Thomas Canam

Thesis Committee Member

Gordon C. Tucker

Abstract

Lateral Organ Boundaries (LBD) gene family encodes transcription factors found only in plants with essential roles in growth, development, and response to biotic and abiotic factors. The sunflower (Helianthus annuus L., Asteraceae family) LBD genes were studied using different in silico and phylogenetic approaches including four major steps: gene identification, phylogenic analysis, structural analysis, and expression analysis. Sixty-four sunflower LBD genes (HaLBDs) were identified using query search of all Arabidopsis LBD genes against sunflower genome (version r1.2) followed by LBD domain sequence verification. A phylogenetic tree was reconstructed using MEGA-X program. The identified genes were phylogenetically classified into two main clades (Class I and Class II), consistent with phylogeny in all other studied plant species. Using GFF3 (General Feature Format) annotation, chromosomal locations were retrieved and mapped to the chromosomes using the MapDraw tool, as well as the gene structure of the HaLBD genes was generated with the GSDS (Gene Structure Display Server). The chromosomal analysis indicated unequally distribution of the LBD genes among all seventeen chromosomes. Sunflower LBD gene expression were studied using publicly available RNA-sequencing repositories (The Bio-Analytical Resource for Plant Biology - BAR), including stem, bract, leaves, ligule, corolla, ovary, seed, stamen, pollen, and style. In total 21 LBD genes were identified as expressed in at least one tissue/organ. The majority of the expressed HaLBD genes had distinct expression levels and displayed a wide range of tissue-specific expression. Additionally, we cloned a dominant-negative modified version of an HaLBD16 which will allow further functional studied of this gene. Our data will provide future reference for the sunflower functional characterization and biotechnological improvement.

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