Interaction of ibr5 and small GTP-binding Proteins in Growth and Development of Arabidopsis




Ahmad, Idrees Ijaz

Journal Title

Journal ISSN

Volume Title



Auxin is a plant hormone that regulates plant growth and development. Auxin controls the expression of auxin-responsive genes by regulating the degradation of a group of transcriptional repressor proteins known as Aux/IAAs via the ubiquitin-proteasome pathway involving nuclear auxin receptors. Recent studies have demonstrated that a dual-specificity phosphatase, INDOLE 3 BUTYRIC ACID RESPONSE5 (IBR5) is involved in auxin signaling. According to our yeast two-hybrid screen, in vitro binding assays, and coimmunoprecipitation studies, IBR5 physically interacts with several small GTP binding proteins. Previous studies indicate that small GTP binding proteins, such as ARA2, ROP2, and ROP6, regulate auxin responses in plants. Data presented here using ibr5/rop2-1 and ibr5/rop6-2 or ibr5/rop2-1/rop6-2 mutant combinations reveals that ibr5-1 is epistatic to both rop2-1 and rop6-2 in root hair formation and leaf epinasty. In addition, plants with ibr5-1 rop2-1 mutations develop longer and narrower petal blades. Interestingly, ara2-3 mutation suppresses both rapid degradation of AUX/IAA repressor proteins in ibr5-4 and the defective physiological and morphological phenotypes of ibr5-4, suggesting that these two proteins may function in a common pathway. Therefore, our biochemical and genetic studies suggest that IBR5 and these GTP binding proteins may function jointly in the auxin signaling pathway.





Ahmad, I. (2019). <i>Interaction of ibr5 and small GTP-binding Proteins in Growth and Development of Arabidopsis</i> (Unpublished thesis). Texas State University, San Marcos, Texas.


Rights Holder

Rights License

Rights URI