Title

Characterization of the Role of JMJ14 in Modulating Plant Defense Responses in Arabidopsis

Date of Award

6-29-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Advisor(s)

Ramesh Raina

Keywords

JMJ14, plant defense, transgenerational defense memory

Abstract

Epigenetic modifications have emerged as an important mechanism to help plants adapt to ever-changing environments. In this work, I examined the role of JMJ14, a Jumonji (JMJ) domain containing H3K4 demethylase, in regulating local and systemic plant defense responses in Arabidopsis, as well as its functions in establishing transgenerational defense memory (TSDM). I also further tested the involvement of JMJ14 in modulating abiotic stresses, especially how it affects plant defense responses under salt stress.

This study revealed that JMJ14 is required for local and systemic resistance and positively modulates transcription and H3K4me3 deposition on Pip biosynthesis gene AGD2-LIKE DEFENSE RESPONSE PROTEIN 1 (ALD1), systemic acquired resistance (SAR) regulator FLAVIN-DEPENDENT MONOOXYGENASE 1 (FMO1) and defense marker PATHOGENESIS-RELATED PROTEIN 1 (PR1). JMJ14 also negatively regulates PR gene repressor SUPPRESSOR OF NPR1-1, INDUCIBLE 1 (SNI1) and mediates the salicylic acid (SA) – pipecolic acid (Pip) defense amplification loop by promoting SA induced ALD1 expression. These results highlight the role of JMJ14 in promoting robustness of plant immune responses. Interestingly, JMJ14 itself is induced by Pip and suppressed by high dosage of SA, implying a negative feedback regulation of defense amplification in Arabidopsis to fine-tune the extent of defense outputs.

I also showed that JMJ14 negatively modulates establishment rate of TSDM. Additionally, JMJ14 was identified as a negative regulator for plant salt tolerance and its presence was shown to enhance disease susceptibility under persistent salt stress.

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