empty pericarp2 Encodes a Negative Regulator of the Heat Shock Response and Is Required for Maize Embryogenesis

Abstract

The heat shock response (HSR) is an evolutionarily conserved molecular/biochemical reaction to thermal stress that is essential to the survival of eukaryotic organisms. Recessive Mutator transposon mutations at the maize empty pericarp2 ( emp2 ) locus led to dramatically increased expression of heat shock genes, retarded embryo development, and early-stage abortion of embryogenesis. The developmental timing of emp2 mutant embryo lethality was correlated with the initial competence of maize kernels to invoke the HSR. Cloning and sequence analyses revealed that the emp2 gene encoded a predicted protein with high similarity to HEAT SHOCK BINDING PROTEIN1, which was first described in animals as a negative regulator of the HSR. emp2 is a loss-of-function mutation of an HSR-negative regulator in plants. Despite the recessive emp2 phenotype, steady state levels of emp2 transcripts were abundant in mutant kernels, and the predicted coding region was unaffected. These expression data suggest that emp2 transcription is feedback regulated, whereas S1 nuclease mapping suggests that emp2 mutant transcripts are 5 Ј truncated and nontranslatable. In support of this model, immunoblot assays revealed that EMP2 protein did not accumulate in mutant kernels. These data support a model whereby an unattenuated HSR results in the early abortion of emp2 mutant embryos. Furthermore, the developmental retardation of emp2 mutant kernels before the HSR suggests an additional role for EMP2 during embryo development distinct from the HSR.

Theglobby1-1(glo1-1) mutation disrupts nuclear and cell division in the developing maize seed causing alterations in endosperm cell fate and tissue differentiation

“…A large number of maize seed mutants have been isolated Scanlon et al, 1994;Sheridan and Neuffer, 1980), although only few have been comprehensively characterised to date (Becraft et al, 2002;Consonni et al, 2003;Fu et al, 2002;Lid et al, 2002;Shen et al, 2003). We describe here the phenotypic characterisation of the glo1-1 mutation, which arose in an active transposon population.…”

Empty Pericarp5Encodes a Pentatricopeptide Repeat Protein That Is Required for Mitochondrial RNA Editing and Seed Development in Maize

“…In maize, three mutants with a similar phenotype have been characterized. Emp2 encodes a repressor of a heat shock response in seeds, mutation of which unleashes a heat shock response causing seed development abortion (Fu et al, 2002). Emp4 encodes a PPR protein that is required for normal level expression of several mitochondrial genes (Gutiérrez-Marcos et al, 2007).…”

The maize duplicate genesnarrow sheath1andnarrow sheath2encode a conserved homeobox gene function in a lateral domain of shoot apical meristems

“…Thus, polyclonal antibodies raised against this peptide antigen are expected to identify epitopes in NS1 as well as NS2 proteins. Proteins were extracted from immature (4-5 cm long) maize female inflorescences (ears) according to the procedures described in Fu et al (Fu et al, 2002). Approximately 30 µg soluble protein was used in western blot analyses; protein gel electrophoresis, transfer, and Coomassie Brilliant Blue staining were performed as described (Sambrook et al, 1989).…”

“…Hybridization probes were radioactively labeled and column-purified as described (Fu et al, 2002). Specific probes used in these analyses were as follows.…”