Investigatng the Role of the NLP7 Transcription Factor in Drought Stress Response in Arabidopsis thaliana
Abstract
Drought and freezing stress are a limiting factor to crop production worldwide. Understanding the mechanisms behind drought and freezing tolerance is critical to the development of crops with improved abiotic stress tolerance. Mutations in the transcription factor NIN- LIKE PROTEIN 7 (NLP7) lead to increased drought tolerance in Arabidopsis. NLP7 is a member of the NLP subfamily of RWP-RK transcription factors and is highly expressed in Arabidopsis root tips and guard cells. We hypothesized that NLP7 regulates drought responses either by modulating stomatal behavior or by altering the expression of genes with roles in drought response pathways. Surprisingly, gravimetric transpiration rate measurements of well-watered plants indicate that nlp7-1 mutants have increased diurnal transpiration rates when compared to wild-type control plants. Coincident with the increased transpiration rate, nlp7-1 plants show an increased stomatal conductance, and increased abaxial and adaxial stomatal density. NLP7 binds to the promoter of genes with roles in abiotic stress responses like ERD15, CBF/DREB1Aand STZ/ZAT10. Expression of the negative regulator of ABA signaling, ERD15, is down in the nlp7-1 plants. The downregulation of ERD15 deregulates ABA signaling resulting in drought and freezing tolerance phenotypes. qRT-PCR gene expression analysis of CBF3/DREB1A showed that it is overexpressed in the nlp7-1 mutant. STZ/ZAT10, a gene regulating ROS detoxification and downstream of CBF3/DREB1A, is upregulated. We observed drought and freezing tolerance phenotypes in nlp7-1, mimicking the phenotypes of the ERD15 knockdown and the 35S:DREB1A overexpressing plants. Our data suggest that NLP7 directly regulates the expression of proteins with roles in drought and freezing stress responses. NLP7 acts as a gatekeeper of the transition from the growth phase to stress response in the plant through a coordinated negative regulation of ABA-dependent and independent abiotic stress response.
Degree
M.S.
Advisors
Iyer-Pascuzzi, Purdue University.
Subject Area
Botany|Plant sciences|Physiology
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