Although cobalt (Co) is indispensable for life, it is toxic to cells when accumulated in excess. The DmeRF system is a well-characterized metal-response system that contributes to Co and nickel resistance in certain bacterial species. The Vibrio parahaemolyticus RIMD 2210633 genome also harbors a dmeRF operon that encodes a multiple antibiotic resistance regulator family transcriptional regulator and a cation diffusion facilitator family protein. Quantitative real-time PCR, growth curves analysis, inductively coupled plasma-mass spectrometry, β-galactosidase activity assays, electrophoretic mobility shift assays, and a mouse infection experiment were performed to characterize the function of the DmeRF system in V. parahaemolyticus. Zinc, copper, and Co significantly increase dmeF expression, with Co inducing the greatest increase. DmeF promotes V. parahaemolyticus growth under high-Co conditions. Additionally, increased accumulation of cellular Co in the ΔdmeF mutant indicates that DmeF is potentially involved in Co efflux. Moreover, DmeR represses the dmeRF operon by binding directly to its promoter in the absence of Co. Finally, the DmeRF system was not required for V. parahaemolyticus virulence in mice. Collectively, our data indicate that the DmeRF system is involved in maintaining Co homeostasis in V. parahaemolyticus and DmeR functioning as a repressor of the operon.

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In the wild type of rice endosperm cell, glutelins and prolamins are synthesized on the respective subdomains of rough endoplasmic-reticulum (ER) and intracellularly compartmentalized into the different storage protein bodies, respectively. Herein, we first report a rice mutation involved in the biogenesis of glutelins and prolamins. A novel mutant for storage proteins was isolated and characterized by the great generation of 57 kD glutelin precursors (proglutelins) and the lacking of 13 kD prolamins. The proteinous alteration was clarified to result from a monogenic mutation with the dosage effect on generation of proglutelins and 13 kD prolamins. This mutation is referred to as GPGG1. A novel ER, the saccular composite-ER, was shown to act in the synthesis of proglutelins and 14 kD prolamins in the mutant. In addition to the composite-ER, the mutant type Golgi, trans-Golgi network, endocytotic protein-storage-vacuole, multivesicular body and lytic vacuole were shown to occur and function in the transfer, exocytosis, endocytosis, delivery, deposition and degradation of storage proteins in the mutant. Moreover, the GPGG1 gene was mapped to a 63.8-kb region of chromosome 12, and a pentatricopeptide repeat-like gene was determined as its candidate gene. Our results reveals that the GPGG1 was involved in the storage protein synthesis and caused the remodeling of endomembrane system for storage protein compartmentation. The candidate gene presumably concerns translation of storage protein mRNAs in rice endosperm cells.