Minisymposium 8: Water & Salinity

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Abs # M0803: A variable cluster of ethylene responsive factor-like genes regulates acclimative responses to submergence in rice

Presenter:	Fukao, Takeshi       Contact Presenter
Authors	Fukao, Takeshi  (A)   Ronald, Pamela C (B)   Mackill, David J (C)   Bailey-Serres, Julia  (A)
Affiliations:	(A): Center for Plant Cell Biology, Department of Botany and Plant Sciences, University of California, Riverside (B): Department of Plant Pathology, University of California, Davis (C): International Rice Research Institute

Flooding occurs commonly by seasonal rainfall and poor drainage. Non-aquatic herbaceous plants are damaged by transient flooding for 24 to 48 h, causing a serious loss of agricultural productivity. Unlike most edible plants, rice is highly tolerant of submergence although rice cultivars range in their tolerance. Submergence 1 (Sub1), a major quantitative trait locus affecting tolerance to complete submergence in lowland rice (Oryza sativa), contains two or three ethylene responsive factor (ERF)-like genes whose transcripts are regulated by submergence. In the submergence intolerant japonica inbred M202, this locus encodes two ERF genes, Sub1B and Sub1C, whereas the tolerant near isogenic line containing the Sub1 locus from the indica FR13A, M202(Sub1), additionally encodes the ERF gene Sub1A. During submergence, the tolerant M202(Sub1) displayed restrained leaf and internode elongation, chlorophyll degradation and carbohydrate consumption, whereas the enzymatic activities of pyruvate decarboxylase and alcohol dehydrogenase were significantly elevated, as compared to the intolerant M202. The transcript levels of genes associated with carbohydrate consumption, ethanolic fermentation and cell expansion were distinctly regulated in the two lines. Sub1A and Sub1C transcript levels were shown to be up-regulated by submergence and ethylene, with the Sub1C allele in M202 also up-regulated by treatment with gibberellic acid (GA). Production of submergence-promoted ethylene and mRNA accumulation of ethylene-responsive genes associated with cell elongation and carbohydrate consumption were suppressed in M202(Sub1). The findings demonstrate that the Sub1 region haplotype determines ethylene- and GA-mediated cellular and developmental responses to submergence through differential expression of Sub1A and Sub1C. Submergence tolerance in lowland rice is conferred by Sub1 haplotype that dampens ethylene production and GA responsiveness causing a quiescence in growth that is correlated with the capacity for re-growth upon de-submergence.