No abstract

[Gd@C82(OH)22]n particles (22 nm in a saline solution) of a dose level as low as 10(-7) mol/kg exhibit a very high antineoplastic efficiency ( approximately 60%) in mice. A dose increment of 1 x 10(-7) mol/kg increases the tumor inhibition rate 26%. [Gd@C82(OH)22]n particles have a strong capacity to improve immunity and interfere with tumor invasion in normal muscle cells, nearly without toxicity in vivo and in vitro. Unlike conventional antineoplastic chemicals, the high antitumor efficiency of nanoparticles is not due to toxic effects to cells because they do not kill the tumor cells directly and only about 0.05% of the used dose is found in the tumor tissues. Results suggest that fullerene derivatives with proper surface modifications and sizes may help realize the dream of tumor chemotherapeutics of high-efficacy and low-toxicity.

Ripening in climacteric fruit requires the gaseous phytohormone ethylene. Although ethylene signaling has been well studied, knowledge of the transcriptional regulation of ethylene biosynthesis is still limited. Here we show that an apple (Malus domestica) ethylene response factor, MdERF2, negatively affects ethylene biosynthesis and fruit ripening by suppressing the transcription of MdACS1, a gene that is critical for biosynthesis of ripening-related ethylene. Expression of MdERF2 was suppressed by ethylene during ripening of apple fruit, and we observed that MdERF2 bound to the promoter of MdACS1 and directly suppressed its transcription. Moreover, MdERF2 suppressed the activity of the promoter of MdERF3, a transcription factor that we found to bind to the MdACS1 promoter, thereby increasing MdACS1 transcription. We determined that the MdERF2 and MdERF3 proteins directly interact, and this interaction suppresses the binding of MdERF3 to the MdACS1 promoter. Moreover, apple fruit with transiently downregulated MdERF2 expression showed higher ethylene production and faster ripening. Our results indicate that MdERF2 negatively affects ethylene biosynthesis and fruit ripening in apple by suppressing the transcription of MdACS1 via multiple mechanisms, thereby acting as an antagonist of positive ripening regulators. Our findings offer a deep understanding of the transcriptional regulation of ethylene biosynthesis during climacteric fruit ripening.