Evidence for a Role of β-subunit Splice Variants in Establishing G-protein Heterotrimer Specificity in Arabidopsis thaliana
Open Access
- Author:
- Dawson, Matthew Zachary
- Area of Honors:
- Biology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Sarah Mary Assmann, Thesis Supervisor
Dr. Bernhard Lüscher, Thesis Honors Advisor - Keywords:
- Arabidopsis thaliana
G-protein
beta-subunit
hormone signaling
receptor-like kinase
yeast 2-hybrid
phenotype assay - Abstract:
- Heterotrimeric G-proteins are involved in a well-conserved signal transduction mechanism in eukaryotic cells, moderating a diverse number of signaling pathways in mammalian and plant systems. In mammalian systems, specificity of G-protein interactions with downstream effectors is achieved through a diverse array of α-, β-, and γ-subunits, allowing for dozens of highly selective G-protein heterotrimers. However, the model plant system Arabidopsis thaliana contains far fewer subunit combinations, suggesting it must have some alternate method of conferring G-protein specificity. We propose that splice variants of the Arabidopsis thaliana G-protein β-subunit may provide a mechanism for establishing this specificity. Phenotype assays of transgenic lines containing only a single A. thaliana β-subunit splice variant revealed that individual splice variants are differentially effective at restoring a wild-type phenotype when inserted in the agb1-2 knockout mutant background. The results of five phenotype assays suggest that the splice variants may act differently on downstream effectors or may act on different downstream effectors entirely. Additionally, a comprehensive yeast-2- hybrid screening of the four splice variants against a cDNA library isolated from Arabidopsis seedlings supports the hypothesis that β-subunit splice variants may provide a mechanism for conferring specificity to the Arabidopsis G-protein signal transduction system.. The results of the yeast 2-hybrid and phenotype assays suggested that at least two splice variants might have differing interacting partners. Moreover, the presence of a diverse population of receptor-like kinases with functions that accompany the functions of G-proteins has implications regarding the nature of G-protein signaling in plants, especially in the ways it differs from the mammalian G-protein signal transduction system.