ABSTRACT
Histone acetylation affects numerous cellular processes, such as gene transcription, in both plants and animals. However, the posttranslational modification-participated regulatory networks for crop-yield-related traits are largely unexplored. Here, we characterize a regulatory axis for controlling rice grain size and yield, centered on a potent histone acetyltransferase (chromatin modifier) known as HHC4. HHC4 interacts with and forms a ternary complex with adaptor protein ADA2 and transcription factor bZIP23, wherein bZIP23 recruits HHC4 to specific promoters, and ADA2 and HHC4 additively enhance bZIP23 transactivation on target genes. Meanwhile, HHC4 interacts with and is phosphorylated by GSK3-like kinase TGW3. The resultant phosphorylation triggers several functional impairments of the HHC4 ternary complex. In addition, we identify two major phosphorylation sites of HHC4 by TGW3-sites which play an important role in controlling rice grain size. Overall, our findings thus have critical implications for understanding epigenetic basis of grain size control and manipulating the knowledge for higher crop productivity.
Subject(s)
Oryza , Animals , Phosphorylation , Oryza/genetics , Oryza/metabolism , Glycogen Synthase Kinase 3/metabolism , Edible Grain/genetics , Edible Grain/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Chromatin/metabolismABSTRACT
Histone chaperones are a group of histone-binding proteins that facilitate the assembly of nucleosomes, the fundamental structural units of chromatin in eukaryotes. In nucleosome assembly, deposition of a histone H3-H4 tetramer onto DNA is the first and critical step, which is mediated by the histone chaperones HIRA and CAF-1. HIRA and CAF-1 are reportedly involved in DNA replication independent (RI) and replication coupled nucleosome assembly, respectively. However, the mechanisms by which they mediate histone deposition remain unclear. In this study, we focused on the mechanism by which HIRA induces RI-nucleosome assembly. We looked for HIRA domains that are required for nucleosome assembly and its localization to chromatin. We used cell-free extracts from Xenopus eggs that carry out RI-nucleosome assembly of plasmid DNA. We confirmed that HIRA formed stable complexes with Asf1, another histone H3-H4 chaperone, and the HIRA-Asf1 complex was solely responsible for RI-nucleosome assembly in egg extracts. We further demonstrated that the HIRA N-terminus containing the WD40 domain, which comprises seven WD40 repeats, and the B domain, to which Asf1 binds, were essential for RI-nucleosome assembly; the three WD40 repeats from the N-terminus were especially critical. Using egg extracts that reproduce nuclear formation accompanying the duplication of chromatin, we also demonstrated that the Hir domain was indispensable for the binding of HIRA to chromatin. Thus, the WD40 and B domains are the core elements for inducing RI-nucleosome assembly. Hir domain regulates the binding to chromatin. Based on these findings, similarities and differences between HIRA and CAF-1 are discussed.
Subject(s)
Cell Extracts , DNA Replication , Histone Chaperones/chemistry , Histone Chaperones/metabolism , Nucleosomes/metabolism , WD40 Repeats , Animals , Cell Cycle Proteins/chemistry , Humans , Oocytes , Transcription Factors/chemistry , Xenopus laevisABSTRACT
The static and dynamic features of magnetization have been investigated in terms of dc magnetization, ac susceptibility, and memory effects on single-layered perovskite La(0.7)Sr(1.3)CoO(4). The results indicate that short-range ferromagnetic clusters coexist with the glassy magnetic state, i.e., a cluster-glass phase between T(f) and T(G) and a spin-glass-like phase below T(f). The clear evidence of memory effects in the dc magnetization is also observed below T(f) and T(G), respectively. These two glassy states with cooperative relaxation processes may derive from the different interaction processes among nanoscale ferromagnetic clusters mediated by the matrix, which is influenced by changing the spin state of Co(3+) ions in spontaneously phase-separated cobaltite.
Subject(s)
Calcium Compounds/chemistry , Cobalt/chemistry , Freezing , Lanthanum/chemistry , Magnetics , Oxides/chemistry , Strontium/chemistry , Titanium/chemistry , Models, MolecularABSTRACT
The ground state Raman spectra of all-trans-beta-carotene in n-hexane and CS2 solutions are measured by simultaneously changing the solvent environment and molecular structure under high hydrostatic pressure. The diverse pressure dependencies of several representative Raman bands are explained using a competitive mechanism involving bond length changes and vibronic coupling. It is therefore concluded that (a) the in-phase C=C stretching mode plays an essential role in the conversion of energy from S1 to S0 states in carotenoids, (b) internal conversion and intramolecular vibrational redistribution can be accelerated by high pressure, and (c) the environmental effect, but not the structural distortion or pi-electron delocalization, is responsible for the spectral properties of a given carotenoid species. These findings revealed the potential of high pressure in exploring the nature of the biological functions of carotenoids.
