Doctoral Dissertations

Date of Award

12-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biochemistry and Cellular and Molecular Biology

Major Professor

Andreas Nebenführ

Committee Members

Brad Binder, Bruce McKee, Elena Shpak, Jennifer Franklin

Abstract

IOJAP protein is found in all organisms that contain a ribosome of bacterial origin. The majority of studies suggest that IOJAP plays a role in translation, although this has yet to be thoroughly investigated in plants. Using Arabidopsis thaliana, an extensive phenotype characterization of iojap mutants was performed. Many processes of plant growth were slightly impaired at optimal temperature (22˚C) but became severely hindered at low temperature (12˚C and 4˚C). These cold temperature defects manifested in an overall reduction of plant growth as well as variegation, chlorosis, leaf hyponasty, as well as reduced maximum quantum yield (Fv/Fm) in young leaves and during de-etiolation. Interestingly other developmental processes such as bolting time, germination, and etiolation were unaffected by low temperature. The observed exacerbation of defects was unique to low temperature as other abiotic stresses such as heat, osmotic, salinity, and high light were ineffective at eliciting similar responses. Tracking relative transcription and translation levels early in de-etiolation, chloroplast encoded transcripts were skewed towards low translation populations, suggesting a translation defect. Further investigation is required to pinpoint the involvement of IOJAP in translation, as well as a better understanding of the detrimental deficiencies brought about by low temperature.

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