A nuclear-encoded protein, mTERF6, mediates transcription termination of rpoA polycistron for plastid-encoded RNA polymerase-dependent chloroplast gene expression and chloroplast development.

The expression of plastid genes is regulated by two types of DNA-dependent RNA polymerases, plastid-encoded RNA polymerase (PEP) and nuclear-encoded RNA polymerase (NEP). The plastid rpoA polycistron encodes a series of essential chloroplast ribosome subunits and a core subunit of PEP. Despite the functional importance, little is known about the regulation of rpoA polycistron. In this work, we show that mTERF6 directly associates with a 3'-end sequence of rpoA polycistron in vitro and in vivo, and that absence of mTERF6 promotes read-through transcription at this site, indicating that mTERF6 acts as a factor required for termination of plastid genes' transcription in vivo. In addition, the transcriptions of some essential ribosome subunits encoded by rpoA polycistron and PEP-dependent plastid genes are reduced in the mterf6 knockout mutant. RpoA, a PEP core subunit, accumulates to about 50% that of the wild type in the mutant, where early chloroplast development is impaired. Overall, our functional analyses of mTERF6 provide evidence that it is more likely a factor required for transcription termination of rpoA polycistron, which is essential for chloroplast gene expression and chloroplast development.

Rubisco accumulation is important for the greening of the fln2-4 mutant in Arabidopsis.

The fructokinase-like protein2 (FLN2) is a component of the PEP complex. FLN2 knockout mutants displayed a delayed greening phenotype on sucrose-containing medium. Our previous work indicated that partial PEP activity is essential for its greening phenotype. In this study, we further report that sufficient Rubisco accumulation is critical for fln2-4 greening. Sugar serves many important functions, such as an energy source and signaling molecule. Through pharmacological experiments using a sugar analog and sugar signaling inhibitor, we demonstrate that sugar serves as energy to support the fln2-4 greening. Seed-reserve and photosynthetic CO2-fixation are the primary energy sources for early seedling growth. No obvious differences were observed in the seed-reserve of the wild-type and fln2-4 by comparing their seed size and dark-germination, indicating that the defective carbon fixation may account for the energy deficit in fln2-4 during its early seedling growth. The Rubisco content was low in fln2-4, but it rapidly accumulated during the greening of fln2-4. Expression of a nuclear-encoded rbcL gene facilitates Rubisco accumulation and partially complements the mutant defects. These results suggest that the Rubisco accumulation is critical for fln2-4 greening. In summary, the rapid Rubisco accumulation that depends on sufficient PEP activity is important for normal seedling growth.

VOPO4 nanosheets as anode materials for lithium-ion batteries.

VOPO4 nanosheets are successfully synthesized using a hydrothermal method followed by calcination. The XRD results reveal that obtained products are crystallized in the orthorhombic VOPO4 phase. SEM and TEM images demonstrate that VOPO4 products possess unique nanosheet morphology. Electrochemical tests show that the VOPO4 nanosheets exhibit an excellent electrochemical performance as anode materials. They can deliver an initial discharge capacity of 1356 mA h g(-1) at 0.1 C, and possess a favorable capacity at rates of 0.2, 1, and 2 C. The synthesized VOPO4 can be used as a good anode material; furthermore, the nanosheet structure can effectively improve the electrochemical performance of this material.