The plant circadian clock regulates autophagy rhythm through transcription factor LUX ARRHYTHMO.

Autophagy is an evolutionarily conserved degradation pathway in eukaryotes; it plays a critical role in nutritional stress tolerance. The circadian clock is an endogenous timekeeping system that generates biological rhythms to adapt to daily changes in the environment. Accumulating evidence indicates that the circadian clock and autophagy are intimately interwoven in animals. However, the role of the circadian clock in regulating autophagy has been poorly elucidated in plants. Here, we show that autophagy exhibits a robust circadian rhythm in both light/dark cycle (LD) and in constant light (LL) in Arabidopsis. However, autophagy rhythm showed a different pattern with a phase-advance shift and a lower amplitude in LL compared to LD. Moreover, mutation of the transcription factor LUX ARRHYTHMO (LUX) removed autophagy rhythm in LL and led to an enhanced amplitude in LD. LUX represses expression of the core autophagy genes ATG2, ATG8a, and ATG11 by directly binding to their promoters. Phenotypic analysis revealed that LUX is responsible for improved resistance of plants to carbon starvation, which is dependent on moderate autophagy activity. Comprehensive transcriptomic analysis revealed that the autophagy rhythm is ubiquitous in plants. Taken together, our findings demonstrate that the LUX-mediated circadian clock regulates plant autophagy rhythms.

Sensitive Detection of Telomerase Based on Hybridization Chain Reaction-assisted Multiple Signal Amplification / 分析化学

A new electrochemical method for telomerase activity assay was developed on the basis of hybridization chain reaction ( HCR)-assisted multiple signal amplification, aiming at improving the sensitivity and specificity of telomerase assay. The experiments utilized HeLa cells as original source of the telomerase in the electrochemical studies. The telomerase primer was firstly self-assembled on the surface of gold electrode. The telomerase catalyzed the elongation of the primer, producing the complementary sequences of hairpin probe H1. In this case, HCR was then initiated by interacting with two hairpin probes H1 and H2. Because both H1 and H2 were modified by biotin, horseradish peroxidase could be captured on the electrode surface through the high-affinity interaction between biotin and streptavidin, catalyzing the oxidation of o-phenylenediamine to produce 2,3-diaminophenazine. Therefore, the telomerase assay was realized by tracing the electrochemical signals with differential pulse voltammetry. This electrochemical method was of high efficiency and feasibility for detecting telomerase activity, and could trace the telomerase activity down to 10 cells/mL HeLa cells with a wide linear range. Besides, it could also easily distinguish the target enzyme from the control proteins with high specificity.