Evolution of the CBL and CIPK gene families in Medicago: genome-wide characterization, pervasive duplication, and expression pattern under salt and drought stress.

BACKGROUND: Calcineurin B-like proteins (CBLs) are ubiquitous Ca2+ sensors that mediate plant responses to various stress and developmental processes by interacting with CBL-interacting protein kinases (CIPKs). CBLs and CIPKs play essential roles in acclimatization of crop plants. However, evolution of these two gene families in the genus Medicago is poorly understood. RESULTS: A total of 68 CBL and 135 CIPK genes have been identified in five genomes from Medicago. Among these genomes, the gene number of CBLs and CIPKs shows no significant difference at the haploid genome level. Phylogenetic and comprehensive characteristic analyses reveal that CBLs and CIPKs are classified into four clades respectively, which is validated by distribution of conserved motifs. The synteny analysis indicates that the whole genome duplication events (WGDs) have contributed to the expansion of both families. Expression analysis demonstrates that two MsCBLs and three MsCIPKs are specifically expressed in roots, mature leaves, developing flowers and nitrogen fixing nodules of Medicago sativa spp. sativa, the widely grown tetraploid species. In particular, the expression of these five genes was highly up-regulated in roots when exposed to salt and drought stress, indicating crucial roles in stress responses. CONCLUSIONS: Our study leads to a comprehensive understanding of evolution of CBL and CIPK gene families in Medicago, but also provides a rich resource to further address the functions of CBL-CIPK complexes in cultivated species and their closely related wild relatives.

Lipopolysaccharide preconditioning attenuates apoptotic processes and improves neuropathologic changes after spinal cord injury in rats.

We have shown earlier that administration of low-dose lipopolysaccharide (LPS) significantly contributed to recovery of motor function after traumatic spinal cord injury in the adult female rat. Using the same standardized animal model, we have now designed a set of experiments to test the hypothesis that LPS preconditioning attenuates stress-related apoptotic processes early after spinal cord trauma. The lower thoracic spinal cord injury in adult female Sprague-Dawley rats was caused by a 10 g weight rod drop from 25 mm on the dural surface of the exposed spinal cord at T10. The rats were randomly assigned to three groups: Sham injury, control (received normal saline alone), and LPS preconditioning (0.2 mg/kg, ip; 72 h prior to the injury). The animals were euthanized at 72 h postinjury. Neuropathologic changes were assessed using hematoxylin and eosin staining. SCI-induced apoptosis were observed by transmission electron microscopy. Caspase-3, cleaved caspase-3, Bax, and Bcl-2 were examined with immunohistochemistry or Western blotting. Compared with the control group, LPS preconditioning group showed significant improvement in the SCI-induced morphology changes. Furthermore, LPS preconditioning reduced the expressions of apoptotic markers caspase-3, cleaved caspase-3, and Bax, upregulated the expression of antiapoptotic marker Bcl-2 in the samples of spinal cord. Low-dose LPS attenuated the recruitment of inflammatory cells and the proliferation of glial cells in the site of injury. LPS preconditioning has neuroprotective effects against TSCI in rats due to its antiapoptosis properties as shown by the inhibition of caspase pathway and the upregulation of antiapoptotic protein.

Lipopolysaccharide preconditioning attenuates neuroapoptosis and improves functional recovery through activation of Nrf2 in traumatic spinal cord injury rats.

The previous studies suggested that low-dose lipopolysaccharide (LPS) provides neuroprotection against subsequent challenge with ischemic/reperfusion injury in the brain. But there were few reports about the neuroprotective effects of low-dose LPS against spinal cord injury (SCI). In this study, we evaluated the effect of low-dose LPS preconditioning on neuroapoptosis status after traumatic SCI (TSCI), using a standardized contusion model (NYU, New York University, impactor). SCI-induced rats were randomly divided into three groups: sham operation, control (receiving only normal saline) and LPS preconditioning (0.2 mg/kg, ip; 72 hours before injury). Neurologic function was assessed by the Basso, Beattie and Bresnahan (BBB) score at 6, 12, 24, 48 and 72 hours after TSCI. Rats were sacrificed at 72 hours postinjury. Histological changes were studied using Nissl staining. Apoptotic neural cells were assessed using the TdT-mediated dUTP Nick End Labeling (TUNEL) assay. Nuclear factor erythroid 2-related factor 2 (Nrf2) and caspase-3 were detected with immunohistochemistry and Western blot. LPS preconditioning reduced neuron apoptosis, improved neurologic outcome and actived Nrf2 expression. Moreover, Histological changes and the number of apoptotic cells were correlated with Nrf2 expression after the rats suffered the SCI. Our results suggest that LPS preconditioning exerted a neuroprotective effect against TSCI in rats, and activation of Nrf2 was believed to be one of the contributing mechanisms.