Age-dependent seasonal growth cessation in Populus.

In temperate and boreal regions, perennial plants adapt their annual growth cycle to the change of seasons. In natural forests, juvenile seedlings usually display longer growth seasons compared to adult trees to ensure their establishment and survival under canopy shade. However, how trees adjust their annual growth according to their age is not known. In this study, we show that age-dependent seasonal growth cessation is genetically controlled and found that the miR156-SPL3/5 module, a key regulon of vegetative phase change (VPC), also triggers age-dependent growth cessation in Populus trees. We show that miR156 promotes shoot elongation during vegetative growth, and its targets SPL3/5s function in the same pathway but as repressors. We find that the miR156-SPL3/5s regulon controls growth cessation in both leaves and shoot apices and through multiple pathways, but with a different mechanism compared to how the miR156-SPL regulon controls VPC in annual plants. Taken together, our results reveal an age-dependent genetic network in mediating seasonal growth cessation, a key phenological process in the climate adaptation of perennial trees.

[Autophagy in hippocampal nerve cells from rats with sepsis-associated encephalopathy].

OBJECTIVE: To show evidence of the autophagy in hippocampal nerve cells from rats with sepsis-associated encephalopathy (SAE) in vivo and to investigate the expression of microtubule-associated protein 1 light chain 3 (LC3). 
 METHODS: A rat model of sepsis was established by the cecal ligation and puncture (CLP). A total of 60 male Wistar rats (30 days old) were randomly divided into a sham group (n=10) and a CLP group (n=50). At 12 hours after CLP, the electroencephalogram (EEG) and somatosensory evoked potential (SEP) changes in rats were monitored and the neurobehavioral score was measured. According to the occurrence of SAE, the CLP group was further divided into an SAE(+) group and an SAE(-) group. Histopathological changes in hippocampus were observed by hematoxylin-eosin staining. An electron microscope was used to observe autophagosome formation and lysosome activation in the hippocampal nerve cells. Expressions of LC3-I and LC3-II protein were measured by Western blot. 
 RESULTS: Five of 50 rats in CLP group died in 12 hours after CLP. According to the low neurobehavioral score and abnormal EEG and SEP, 16 rats were diagnosed as SAE. The incidence of SAE was 35.56% (16/45). Compared with the sham group or the SAE(-) group, the frequency of α wave in SAE(+) group was significantly decreased at 12 hours after CLP, the δ wave increased, the P1 amplitude decreased, and the latency of SEP waves (P1 and N1) was prolonged (P<0.05). The morphology of hippocampal nerve cells was obvious in a status of edema. Pyramidal cells decreased significantly, even dissolved, and cell arrangement was in disorder in the SAE(+) group. But these cells were normal in the sham group and the SAE(-) group. The structure of hippocampal nerve cells was disordered, and the autophagy, granular matrix and square or rectangular crystals were found in the SAE(+) group. However, there was no autophagy both in the sham group and the SAE(-) group. LC3-II/LC3-I ratio in the hippocampal nerve cells was increased significantly at 12 hours after CLP in the SAE(+) group when compared with that in the sham or the SAE(-) group (P<0.05). 
 CONCLUSION: There is autophagy in hippocampal nerve cells from rats with SAE and the LC3-II/LC3-I ratio is increased significantly.

Regulation of autophagy by the nuclear factor κB signaling pathway in the hippocampus of rats with sepsis.

BACKGROUND: Sepsis with brain dysfunction has contributed to an increase risk of morbidity and mortality. In its pathophysiology, both autophagy and nuclear factor κB (NF-κB) have been suggested to play important roles. Based on the fact that crosstalk between autophagy and NF-κB, two stress-response signaling pathways, has been detected in other pathophysiological processes, this study was undertaken to explore the process of autophagy in the hippocampus of septic rats and the role NF-κB plays in the regulation of autophagy during the process. METHODS: Cecal ligation and puncture (CLP) or a sham operation was conducted on male Wistar rats. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of the NF-κB signaling pathway, or a vehicle control, was used to treat with the rats 2 h before the CLP operation. Hematoxylin-eosin staining and biological signal recording was used to measure the morphological and physiological signs of hippocampal dysfunction. An electron microscope was used to observe autophagosome formation and lysosome activation in the hippocampus after CLP. Western blotting and immune histochemistry were used to detect the hippocampus levels of NF-κB and essential proteins involved in formation of the autophagosome (microtubule-associated protein light chain 3 (LC3), Beclin1, Lamp-1, and Rab7). RESULTS: Compared with sham-operated rats, the CLP rats showed decreasing mean arterial pressure (MAP), increasing heart rate (HR), and pathological histological changes. CLP rats exhibited not only increased vacuolization through electron micrographs but also increased LC3-II, decreased Beclin1, LAMP-1, and Rab7 through the immunofluorescence and Western blot. However, PDTC + CLP rats revealed that inhibition of the NF-κB signal axis by PDTC increased the levels of LC3-II, Beclin1, LAMP-1, and Rab7 and improved physiological function including blood pressure and heart rate. CONCLUSIONS: The autophagy process during the hippocampus of CLP rats might be blocked by the activation of NF-κB signaling pathway. Inhibition of NF-κB signaling pathway could enhance the completion of autophagy with a neuroprotective function in septic brains.