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Date of Award

9-2011

Document Type

Campus Access

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Plant Biology

First Advisor

Om Parkash Dhankher

Second Advisor

Alice Cheung

Third Advisor

Danny Schnell

Subject Categories

Genetics | Molecular Biology | Plant Biology

Abstract

Abiotic stresses such as drought, salt, cold, heat and exposure to toxic metals adversely affect growth and productivity of crop plants and are serious threats to agriculture. Members of Stress Associated Protein (SAP) family in rice have been shown to provide tolerance to multiple abiotic stresses. There are 18 and 14 reported members of SAP family in rice and Arabidopsis, respectively. These SAPs contain A20, AN1, or both A20/AN1 zinc finger domains at the N- or C-terminus. Some members of SAP family proteins also contain extra Cys2-His2 RING motifs on the C-terminus.

We describe here the functional characterization of two novel SAP genes, AtSAP10 and AtSAP11, fromArabidopsis thaliana ecotype Columbia. AtSAP10 gene contains an A20 and AN1 zinc-finger domain at the N- and C-terminal, respectively. Arabidopsis SAP10 showed differential regulation by various abiotic stresses such as heavy metals and metalloids (Ni, Cd, Mn, Zn, and As), high and low temperatures, cold, and ABA. Overexpression of AtSAP10 in Arabidopsis conferred strong tolerance to heavy metals such as Ni, Mn, and Zn and to high temperature stress. AtSAP10 transgenic plants under these stress conditions grew green and healthy, attained several-fold more biomass, and had longer roots as compared to wild type plants. Further, while these transgenic plants accumulated significantly greater amounts of Ni and Mn in both shoots and root tissues, there was no significant difference in the accumulation of Zn. AtSAP10 promoter-GUS fusion studies revealed a root and floral organ-specific expression of AtSAP10. Overexpression of AtSAP10-GFP fusion protein showed the localization in both nucleus and cytoplasm.

A second gene from AtSAP family, AtSAP11, contains two AN1 zinc finger domains at N-terminal and two C2H2 zinc finger domains at C-terminus. Arabidopsis SAP11 showed differential regulation by various abiotic stresses such as heavy metals and metalloids (As, Cd and Zn), high and low temperatures, cold, and salt. Overexpression of AtSAP11 in Arabidopsis conferred moderate tolerance to heavy metals As and Zn and slightly enhanced tolerance to drought stress. AtSAP11 overexpression plants did not accumulate significantly higher amounts arsenic in shoots or roots. AtSAP11 promoter-GUS fusion studies revealed a floral organ-specific and fruit specific expression of AtSAP11. AtSAP11-GFP fusion showed an ER like localization of the fusion protein. Thus these results showed that AtSAP10 and AtSAP11 are potentially useful candidate genes for engineering tolerance to heavy metals and to abiotic stress in cultivated plants.

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