Salinity is one of the major abiotic stresses that impacts plant growth and reduces the productivity of field crops. Compared to field plants, test tube plantlets offer a direct and fast approach to investigate the mechanism of salt tolerance. Here we examined the ultrastructural and physiological responses of potato (Solanum tuberosum L. c.v. “Longshu No. 3”) plantlets to gradient saline stress (0, 25, 50, 100, and 200 mM NaCl) with two consequent observations (2 and 6 weeks, respectively). The results showed that, with the increase of external NaCl concentration and the duration of treatments, (1) the number of chloroplasts and cell intercellular spaces markedly decreased, (2) cell walls were thickened and even ruptured, (3) mesophyll cells and chloroplasts were gradually damaged to a complete disorganization containing more starch, (4) leaf Na and Cl contents increased while leaf K content decreased, (5) leaf proline content and the activities of catalase (CAT) and superoxide dismutase (SOD) increased significantly, and (6) leaf malondialdehyde (MDA) content increased significantly and stomatal area and chlorophyll content decline were also detected. Severe salt stress (200 mM NaCl) inhibited plantlet growth. These results indicated that potato plantlets adapt to salt stress to some extent through accumulating osmoprotectants, such as proline, increasing the activities of antioxidant enzymes, such as CAT and SOD. The outcomes of this study provide ultrastructural and physiological insights into characterizing potential damages induced by salt stress for selecting salt-tolerant potato cultivars.
Plant-parasitic nematodes cause serious crop losses worldwidely. This study intended to discover the antagonistic mechanism of Bacillus cereus strain S2 against Meloidogyne incognita. Treatment with B. cereus strain S2 resulted in a mortality of 77.89% to Caenorhabditis elegans (a model organism) and 90.96% to M. incognita. In pot experiment, control efficiency of B. cereus S2 culture or supernatants were 81.36% and 67.42% towards M. incognita, respectively. In field experiment, control efficiency was 58.97% towards M. incognita. Nematicidal substances were isolated from culture supernatant of B. cereus S2 by polarity gradient extraction, silica gel column chromatography and HPLC. Two nematicidal compounds were identified as C16 sphingosine and phytosphingosine by LC-MS. The median lethal concentration of sphingosine was determined as 0.64 μg/ml. Sphingosine could obviously inhibit reproduction of C. elegans, with an inhibition rate of 42.72% for 24 h. After treatment with sphingosine, ROS was induced in intestinal tract, and genital area disappeared in nematode. Furthermore, B. cereus S2 could induce systemic resistance in tomato, and enhance activity of defense-related enzymes for biocontrol of M. incognita. This study demonstrates the nematicidal activity of B. cereus and its product sphingosine, as well provides a possibility for biocontrol of M. incognita.
Drought and soil salinity reduce agricultural output worldwide. Plant-growth-promoting rhizobacteria (PGPR) can enhance plant growth and augment plant tolerance to biotic and abiotic stresses. Haloxylon ammodendron, a C4 perennial succulent xerohalophyte shrub with excellent drought and salt tolerance, is naturally distributed in the desert area of northwest China. In our previous work, a bacterium strain numbered as M30-35 was isolated from the rhizosphere of H. ammodendron in Tengger desert, Gansu province, northwest China. In current work, the effects of M30-35 inoculation on salt tolerance of perennial ryegrass were evaluated and its genome was sequenced to identify genes associated with plant growth promotion. Results showed that M30-35 significantly enhanced growth and salt tolerance of perennial ryegrass by increasing shoot fresh and dry weights, chlorophyll content, root volume, root activity, leaf catalase activity, soluble sugar and proline contents that contributed to reduced osmotic potential, tissue K+ content and K+/Na+ ratio, while decreasing malondialdehyde (MDA) content and relative electric conductivity (REC), especially under higher salinity. The genome of M30-35 contains 4421 protein encoding genes, 12 rRNA, 63 tRNA-encoding genes and four rRNA operons. M30-35 was initially classified as a new species in Pseudomonas and named as Pseudomonas sp. M30-35. Thirty-four genes showing homology to genes associated with PGPR traits and abiotic stress tolerance were identified in Pseudomonas sp. M30-35 genome, including 12 related to insoluble phosphorus solubilization, four to auxin biosynthesis, four to other process of growth promotion, seven to oxidative stress alleviation, four to salt and drought tolerance and three to cold and heat tolerance. Further study is needed to clarify the correlation between these genes from M30-35 and the salt stress alleviation of inoculated plants under salt stress. Overall, our research indicated that desert shrubs appear rich in PGPRs that can help important crops tolerate abiotic stress.
Hydatidiform mole (HM) is a human pregnancy with abnormal embryonic development. NLRP7 is a major autosomal recessive gene responsible for recurrent molar pregnancies and associated reproductive wastage in patients from several populations. Here, we report NLRP7 mutation analysis in 35 unrelated Chinese patients with recurrent reproductive wastage, including at least one HM. We describe three new protein-truncating mutations in NLRP7 and show the presence of three founder mutations in China and Asian populations. We determined the parental contribution to six molar tissues and show the occurrence of three diploid androgenetic moles in patients with one defective allele, while three diploid biparental moles occurred in patients with two defective alleles. We document the failure of pregnancies after assisted reproductive technologies (ARTs) in three patients with two defective alleles each and a successful pregnancy in one of two patients with one defective allele. Our data suggest that patients with a single defective allele have better reproductive outcomes than patients with two defective alleles, and some of them may benefit from ART.
Early pregnancy loss (EPL) is one of the most common complications of human reproduction. Combined with our previous proteomic studies on villous and decidual tissues of EPL, we found that alterations of the proteins involved in oxidative stress (OS), unfolded protein response (UPR) and proteolysis presented a complex and dynamic interaction at the maternal-fetal interface. In the present study, we developed a cell model of OS using normal decidual cells to examine cell viability and expression levels of proteins related to endoplasmic reticulum stress (ER stress) and UPR. We found that glucose regulated protein 78 (GRP 78) and ubiquitinated proteins were significantly up-regulated in hydrogen peroxide (H(2)O(2)) treated decidual cells in a dose-dependent manner. Excessive OS could influence proper function of UPR by decreasing VCP in decidual cells, thereby leading to cell damage as well as inhibition of cell growth and activation of apoptosis. Furthermore, when pretreated with MG 132, a pharmacological inhibition of the proteasome, the H(2)O(2) treated decidual cells became less viable and could not up-regulate the expression level of GRP 78 to resolve the protein-folding defects, which indicating that malfunction of UPR in decidual cells might aggravate the inhibitory effect of OS in decidual cells. The present results reveal that abnormal protein profiles associated with OS induced ER stress and malfunction of UPR might be involved in the development of EPL, and OS and ER stress are potential targets for pregnant care and prognosis in normal pregnancy and its disorders.
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