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Transcription factor networks regulating SAG21: An arabidopsis gene at the interface between stress and senescence

Nayakoti, Swapna 2020. Transcription factor networks regulating SAG21: An arabidopsis gene at the interface between stress and senescence. PhD Thesis, Cardiff University.
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Abstract

SAG21/AtLEA5 is an Arabidopsis thaliana gene belonging to the late embryogenesis associated (LEA) protein family. Prior research identified tissue specific, spatial and temporal expression of the SAG21 promoter. A 1685 bp upstream region of SAG21 contains cis elements that act as binding sites for several transcription factor families. The aim here was to investigate the transcription factor network regulating SAG21 in response to senescence, development and stress responses. To investigate if transcription factors identified in a yeast- 1-hybrid screen regulate SAG21, expression of SAG21 was analysed in transcription factor mutants of WRKY 15, 63 and 67 under abiotic stresses known to elicit SAG21 expression. WRKY15 was not essential for induction of the SAG21 expression. WRKY63 functioned as a negative regulator of the SAG21 expression under drought stress. WRKY67 may act as a positive or negative regulator of SAG21 under salt stress. SAG21 promoter deletion-GUS reporter constructs were used to understand the role of the cis-elements in regulating senescence and wounding responses. SAG21 showed different expression patterns in floral organs of the deletion constructs. The role of kinetin in regulating senescence and wounding responses was studied in young and older cotyledons and in four-week old wounded leaves. Kinetin inhibited senescence-related and wound-induced SAG21 expression. Induction of SAG21 expression by wounding was dependent on the age of wounded rosette. Overexpression of SAG21 under its own promoter in optimal conditions produced similar primary root length, more lateral roots, and greater lateral root length compared to overexpression of SAG21 from the 35S constitutive promoter. Under oxidative stress SAG21 transgenic over expressors lines produced increased primary root length under all concentrations of H2O2 whereas the number of lateral roots and length of lateral roots was greater on lower concentrations of H2O2.Together, these data suggest effects of specific SAG21 promoter regions on development and stress responses.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > Q Science (General)
Date of First Compliant Deposit: 16 June 2020
Last Modified: 10 Jun 2023 01:51
URI: https://orca.cardiff.ac.uk/id/eprint/132472

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