Poster: Intracellular Signaling

Abs # 843: Rop GTPase-Regulated Hypoxia Tolerance in Arabidopsis: Genetic and Genomic Analysis of Regulatory and Metabolic Responses

Presenter:	Branco-Price, Cristina , crisbp@citrus.ucr.edu
Authors	Branco-Price, Cristina  (B) (A)  Baxter-Burrell, Airica  (A)   Ferreira, Ricardo B. (B)   Bailey-Serres, Julia  (A)
Affiliations:	(A): University of California, Riverside (B): Instituto de Tecnologia Química e Biológica, Portugal

Arabidopsis thaliana seedling tolerance of transient low oxygen stress (hypoxia) requires regulated RopGTPase activation of a DPI-sensitive NADPH oxidase that results in hydrogen peroxide production and moderate induction of alcohol dehydrogenase (ADH) mRNA levels and enzymatic activity (Baxter-Burrell et al., 2002, Science 296:2026-28). A knockout of Rop GTPase activating protein (ropgap4-1) results in super-induction of ADH and reduced hypoxia tolerance. ROPGAP4 is a negative regulator of Rop signaling; negative-feedback regulation of Rop signaling occurs under hypoxia by Rop-mediated activation of ROPGAP4 expression. DNA microarray (Affymetrix 25K GeneChip) analysis of control and hypoxia-treated seedlings was performed to evaluate: (1) translational regulation, by comparison of the relative abundance of total and polysomal mRNA in WT, and (2) negative regulation of Rop signaling, by comparison of mRNA levels in WT and ropgap4-1. We confirmed that regulation of initiation of mRNA translation is a significant component of the stress response. Differential regulation of mRNA abundance and translation was evident for genes encoding proteins involved in (1) carbohydrate consumption and ethanolic fermentation (sucrose synthase, pyruvate decarboxylase, ADH), (2) oxidative stress signaling and reactive oxygen species elimination (NADPH oxidase subunits, superoxide dismutase, glutathione-S-transferase, peroxidase), (3) protein turnover (F-box and SKP), and (4) gene transcription (WRKY, MYB, MADS). Genetic and molecular analyses are underway to confirm and investigate the significance of these Rop-regulated genes/mechanisms in the response to hypoxia. Research supported by NSF (MCB-131486) and Portugal’s FCT- Ministério da Ciência e Tecnologia (SFRH/BD/9165/2002).