Naslov
Characterization of regulatory switches essential for the control of PIN gene expression in Arabidopsis thaliana

Autori
Malenica, Nenad

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Universität für Bodenkultur Wien

Mjesto
Beč

Datum
20.12

Godina
2004

Stranica
151

Mentor
Prof. Dr. Josef Glößl

Neposredni voditelj
Dr. Christian Luschnig

Ključne riječi
transport auksina; gravitropizam; polarnost
(auxin transport; gravitropism; polarity)

Sažetak
The small family of PIN proteins from Arabidopsis thaliana is crucial for establishment and maintenance of auxin gradients in the plant. Specifically, their - predominantly - polar localization in cell membranes, and phenotypes of corresponding mutants, makes them the most likely candidates for being polar transporters of auxin. Auxin gradients, presumably generated by the action of these PIN transporters are essential for a plethora of plant physiological processes. Nevertheless, regulatory mechanisms that affect expression and/or activity of the putative auxin carriers are only beginning to be understood. This work describes a genetic approach to characterize effectors of the EIR1/PIN2 auxin efflux carrier in A. thaliana. Recessive mutations, representing two complementation groups (soe2-1 and soe3-1, for SUPPRESSOR OF EIR1), could be identified in the screen. Both mutants exhibit a number of phenotypes that link the role of the corresponding gene products specifically to the regulation of auxin transport. In line with this hypothesis, growth of both soe mutants is hypersensitive to inhibitors of polar auxin transport, while responsiveness to auxin and other growth regulators is not altered. In addition, DR5rev::GFP expression levels are reduced in soe roots, presumably reflecting decreased auxin levels. Finally, transport measurements performed with labeled auxin demonstrated that polar auxin transport is reduced in the soe mutants. The deficiencies in polar auxin transport correlate with mis-expression of PIN proteins in soe2-1 and soe3-1, indicating that the observed reduction in PIN1 and PIN7 protein levels could be responsible for reduced auxin transport and soe mutant-phenotypes. In another project a constitutively expressed EIR1-GFP reporter construct was generated to investigate post-transcriptional regulation of EIR1. It was found that overexpressed EIR1-GFP can rescue the agravitropic phenotype of the eir1-4 mutant, a response that seemingly relates to a controlled proteolytic turnover of the reporter protein. A possible involvement of the 26S proteasome degradation pathway in the proteolytic control of EIR1-GFP is demonstrated by proteasome inhibitor treatments that lead to increased EIR1-GFP protein levels in the root. Furthermore, analysis of EIR1-GFP distribution, and immunolocalization of EIR1 in gravity-stimulated roots, indicate that proteolytic turnover of EIR1 might control root gravitropism. Schlagworte

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA