Physiological mechanisms for plant distribution pattern: responses to flooding and drought in three wetland plants from Dongting Lake, China

Both flooding and drought are important in determining plant distribution in wetlands. However, the roles of plant’s physiological response to flooding and drought in accounting for plant distribution are far from clear. To this end, three typical wetland plants with different distribution patterns (high-elevation species Miscanthus sacchariflorus, low-elevation species Carex brevicuspis and Polygonum hydropiper) in Dongting Lake were treated with three water levels (flooding 25 cm, control 0 cm, drought ?25 cm), and relative growth rate (RGR), malondialdehyde (MDA) content, electrolyte leakage and proline content were investigated. The RGR of the three species decreased significantly in both flooding and drought treatments. Compared to the control, the RGR of M. sacchariflorus decreased more in the flooding treatment but less in the drought treatment compared to the other two species. The contents of MDA in the three species increased in both flooding and drought treatments, except for P. hydropiper in the flooding treatment. MDA contents increased more in M. sacchariflorus in the flooding treatment but less in the drought treatment compared to the other two species. Only M. sacchariflorus had a higher electrolyte leakage in the flooding treatment, and drought led to a higher electrolyte leakage in P. hydropiper and C. brevicuspis. Proline content increased 69.2, 66.7 and 39.6 % in P. hydropiper, C. brevicuspis and M. sacchariflorus in the flooding treatment, and increased 44.2, 13.0 and 45.3 % in the drought treatment, respectively. These results suggest that M. sacchariflorus has a higher tolerance to drought but a lower tolerance to flooding than do the other two species, which might be the intrinsic mechanisms accounting for their different distribution patterns.     

Mediator mechanisms involved in TRPV1 and P2X receptor-mediated, ROS-evoked bradypneic reflex in anesthetized rats.

Inhalation of H2O2 is known to evoke bradypnea followed by tachypnea, which are reflexes resulting from stimulation by reactive oxygen species of vagal lung capsaicin-sensitive and myelinated afferents, respectively. This study investigated the pharmacological receptors and chemical mediators involved in triggering these responses. The ventilatory responses to 0.2% aerosolized H2O2 were studied before and after various pharmacological pretreatments in anesthetized rats. The initial bradypneic response was reduced by a transient receptor potential vanilloid 1 (TRPV1) receptor antagonist [capsazepine; change (Delta) = -53%] or a P2X purinoceptor antagonist [iso-pyridoxalphosphate-6-azophenyl-2',5'-disulphonate (PPADS); Delta = -47%] and was further reduced by capsazepine and iso-PPADS in combination (Delta = -78%). The initial bradypneic response was reduced by a cyclooxygenase inhibitor (indomethacin; Delta = -48%), ATP scavengers (apyrase and adenosine deaminase in combination; Delta = -50%), or capsazepine and indomethacin in combination (Delta = -47%), was further reduced by iso-PPADS and indomethacin in combination (Delta = -75%) or capsazepine and ATP scavengers in combination (Delta = -83%), but was not affected by a lipoxygenase inhibitor (nordihydroguaiaretic acid) or by any of the various vehicles. No pretreatment influenced delayed tachypnea. We concluded that 1) the initial bradypneic response to H2O2 results from activation of both TRPV1 and P2X receptors, possibly located at terminals of vagal lung capsaicin-sensitive afferent fibers; 2) the functioning of the TRPV1 and P2X receptors in triggering the initial bradypnea is, in part, mediated through the actions of cyclooxygenase metabolites and ATP, respectively; and 3) these mechanisms do not contribute to the H2O2-evoked delayed tachypnea.     

Positive Charges on Lysine Residues of the Extrinsic 18 kDa Protein Are Important to Its Electrostatic Interaction with Spinach Photosystem Ⅱ Membranes

To determine the contribution of charged amino acids to binding with the photosystem II complex （PSII）, the amino or carboxyl groups of the extrinsic 18 kDa protein were modified with N- succinimidyl propionate （NSP） or glycine methyl ester （GME） in the presence of a water-soluble carbodiimide, respectively. Based on isoelectric point shift, 4-10 and 10-14 amino groups were modified in the presence of 2 and 4 mM NSP, respectively. Similarly, 3-4 carboxyl groups were modified by reaction with 100 mM GME. Neutralization of negatively charged carboxyl groups with GME did not alter the binding activity of the extrinsic 18 kDa protein. However, the NSP-modified 18 kDa protein, in which the positively charged amino groups had been modified to uncharged methyl esters, failed to bind with the PSII membrane in the presence of the extrinsic 23 kDa protein. This defect can not be attributed to structural or conformational alterations imposed by chemical modification, as the fluorescence and circular dichroism spectra among native, GME- and NSP-modified extrinsic 18 kDa proteins were similar. Thus, we have concluded that the positive charges of lysyl residues in the extrinsic 18 kDa protein are important for its interaction with PSII membranes in the presence of the extrinsic 23 kDa protein. Furthermore, it was found that the negative charges of carboxyl groups of this protein did not participate in binding with the extrinsic 23 kDa protein associated with PSII membranes.     

FGF1 improves functional recovery through inducing PRDX1 to regulate autophagy and anti‐ROS after spinal cord injury

Fibroblast growth factor 1 (FGF1) is thought to exert protective and regenerative effects on neurons following spinal cord injury (SCI), although the mechanism of these effects is not well understood. The use of FGF1 as a therapeutic agent is limited by its lack of physicochemical stability and its limited capacity to cross the blood‐spinal cord barrier. Here, we demonstrated that overexpression of FGF1 in spinal cord following SCI significantly reduced tissue loss, protected neurons in the ventricornu, ameliorated pathological morphology of the lesion, dramatically improved tissue recovery via neuroprotection, and promoted axonal regeneration and remyelination both in vivo and in vivo. In addition, the autophagy and the expression levels of PRDX1 (an antioxidant protein) were induced by AAV‐FGF1 in PC12 cells after H₂O₂ treatment. Furthermore, the autophagy levels were not changed in PRDX1‐suppressing cells that were treated by AAV‐FGF1. Taken together, these results suggest that FGF1 improves functional recovery mainly through inducing PRDX1 expression to increase autophagy and anti‐ROS activity after SCI.     

Role of two-component regulatory systems in intracellular survival of Mycobacterium tuberculosis

The typical two-component regulatory systems (TCSs), consisting of response regulator and histidine kinase, play a central role in survival of pathogenic bacteria under stress conditions such as nutrient starvation, hypoxia, and nitrosative stress. A total of 11 complete paired two-component regulatory systems have been found in Mycobacterium tuberculosis, including a few isolated kinase and regulatory genes. Increasing evidence has shown that TCSs are closely associated with multiple physiological process like intracellular persistence, pathogenicity, and metabolism. This review gives the two-component signal transduction systems in M. tuberculosis and their signal transduction roles in adaption to the environment.     

Enhanced γ-aminobutyric acid-forming activity of recombinant glutamate decarboxylase (gadA) from Escherichia coli

γ-aminobutyric acid (GABA) is an important bioactive regulator, and its biosynthesis is primarily through the α-decarboxylation of glutamate by glutamate decarboxylase (GAD). The procedures to obtain GABA by bioconvertion with high activity recombinant Escherichia coli GAD have been seldom understood. In this study, Escherichia coli GAD (gadA) was highly expressed (about 70–75% of total protein) as soluble protein in Escherichia coli BL21(DE3) containing pET28a-gadA, which was induced by 0.4 mM IPTG in LB medium, and maximal GABA-forming activity of the recombinant GAD was 40 U/mL at a concentration (0.15 mM) of pyridoxal phosphate (PLP) and a concentration (0.6 mM) of Ca²⁺ at optimal pH of 3.8. The optimal concentration (7.5 mM) of Mn²⁺ can also improve the activity of recombinant enzyme, but the co-effect of Ca²⁺ and Mn²⁺ exhibited antagonism effect when added simultaneously. LB and 0.1% (w/v) lactose were selected as culture medium and inducer, respectively. The relative activity was markedly higher activated by Ca²⁺ (174%), Mn²⁺ (164%) than that by other seven bivalent cations. Finally, the yield of GABA was high of 94 g/L detected by paper chromatography or HPLC in 1 L reaction system with 30 mL crude GAD (12 U/mL). By entrapping Escherichia coli glutamate decarboxylase into sodium alginate and carrageenan gel beads, the activity of immobilized GAD (IGAD) remained 85% during the initial five batches and the activity still remained 50% at the tenth batch, these results indicated that the recombinant Escherichia coli GAD was feasible for the future industrial production of GABA.     

石灰石粉施用剂量对重庆酸雨区受害 马尾松林细根生长的影响

马尾松(Pinus massoniana)为重庆的重要乡土树种和主要造林树种,担负着特殊而重要的生态环境保全功能,但在酸雨的长期影响下,其健康状况持续低下。为探究不同剂量石灰石粉对马尾松细根生长的影响,给受害马尾松纯林的恢复与管理提供科学依据,2004年5月在属于酸雨区的重庆市江北区铁山坪林场,采用随机区组设计,设立在马尾松纯林酸化土壤表面一次性撒施石灰石粉0(不撒施对照)、1、2、3,4t/hm² 5个处理的长期定位观测试验。2006年10月的监测结果表明,与对照相比,撒施石灰石粉可明显促进腐殖质层和0-20、20-40、40-60cm土层马尾松细根的生长(P < 0.05),尤其是改善腐殖质层和20-40、40-60cm的根量,在腐殖质层和0-60cm马尾松细根的干重总密度、长度总密度、表面积总密度、体积总密度和根尖总密度与对照各项密度指标对应值的比值,1t/hm²下分别为1.53、1.34、1.39、1.24,1.48,2t/hm²下分别为2.05、1.83、1.94、1.79,2.04,3t/hm²下分别为2.17、2.02、2.02、1.78,2.32,4t/hm²下分别为2.68、2.52、2.62、3.70和2.71,改善效果总体上随撒施剂量增大而增强。从有限时间(2-3a)内观测的根系生长改善效果与经济投入的比值来看,建议一次性撒施的最佳剂量为2t/hm²,但在考虑时间加长情况下,效果最好和最经济的剂量还有待后续研究。