Involvement of a rice mutation in storage protein biogenesis in endosperm and its genomic location.

MAIN CONCLUSION: A mutation was first found to cause the great generation of glutelin precursors (proglutelins) in rice (Oryza sativa L.) endosperm, and thus referred to as GPGG1. The GPGG1 was involved in synthesis and compartmentation of storage proteins. The PPR-like gene in GPGG1-mapped region was determined as its candidate gene. In the wild type rice, glutelins and prolamins are synthesized on respective subdomains of rough endoplasmic reticulum (ER) and intracellularly compartmentalized into different storage protein bodies. In this study, a storage protein mutant was obtained and characterized by the great generation of proglutelins combining with the lacking of 13 kD prolamins. A dominant genic-mutation, referred to as GPGG1, was clarified to result in the proteinous alteration. Novel saccular composite-ER was shown to act in the synthesis of proglutelins and 14 kD prolamins in the mutant. Additionally, a series of organelles including newly occurring several compartments were shown to function in the transfer, trans-plasmalemmal transport, delivery, deposition and degradation of storage proteins in the mutant. The GPGG1 gene was mapped to a 67.256 kb region of chromosome 12, the pentatricopeptide repeat (PPR)-like gene in this region was detected to contain mutational sites.

pH-Responsive shrinkage/swelling of a supramolecular hydrogel composed of two small amphiphilic molecules.

A pH-responsive volume-change function was successfully introduced into a supramolecular hydrogel that contained GalNAc-appended (GalNAc=N-acetylgalactosamine) glutamate ester 1 by the simple mixing of it with an appropriate amount of 2 a or 2 b amphiphilic carboxylic acid. In the 1:1 mixture (1:2), the hydrogel swelled under neutral pH conditions, but shrank to almost half of its original volume under acidic pH conditions. The structure and pH response of the mixed hydrogel were characterized by using X-ray diffraction (XRD), confocal laser scanning microscopy (CLSM), transmission or scanning electron microscopy (TEM, SEM), and Fourier transform IR (FTIR) spectroscopy. Well-developed fibers formed a stable hydrogel by self-assembly, and under acidic conditions the charge of the carboxylic acid terminal (from the carboxylate anion) was neutralized and then these fibers became densely packed. This macroscopic pH response was also applied to the pH-triggered release of bioactive substances. In this mixed supramolecular hydrogel, the hydrogelator 1 provides a stable hydrogel structure and the additive 2 acts as a commander that is sensitive to an environmental pH signal. The present supramolecular copolymerization strategy should be useful for the construction of novel, stimuli-responsive, soft materials.