Antimicrobial Peptides from the Plants

AMPs （antimicrobial peptides） are small, mostly basic peptides that range in size from 2-9 kDa, and they are an important component of the innate defense system of plants where they are effector molecules considered to be an important defense barrier to pathogens and pests. Nine families of antimicrobial peptides have been identified in plants, including thionins, defensins, lipid transfer proteins, hevein and knotting-like peptides, four cysteine-types, and the recently reported shepherdins, snakins and cyclotides. They are part of both permanent and inducible defense barriers of plants. Transgenic overexpression of the corresponding genes leads to enhanced tolerance to pathogens, and peptide-sensitive pathogen mutants have reduced virulence. In this review, the recent studies on peptides from plant sources, including peptides isolated from indigenous medicine and edible plants of Central-Asia, are briefly discussed with a focus on their origins, antioxidant, antitumor activities and the possible mechanisms of actions in order to provide a profile of important plant peptides.

Salt Stress in Arabidopsis： Lipid Transfer Protein AZI1 and Its Control by Mitogen-Activated Protein Kinase MPK3

A plant＇s capability to cope with environmental challenges largely relies on signal transmission through mitogen-activated protein kinase （MAPK） cascades. In Arabidopsis thaliana, MPK3 is particularly strongly associated with numerous abiotic and biotic stress responses. Identification of MPK3 substrates is a milestone towards improving stress resistance in plants. Here, we characterize AZI1, a lipid transfer protein （LTP）-related hybrid proline-rich protein （HyPRP）, as a novel target of MPK3. AZI1 is phosphorylated by MPK3 in vitro. As documented by co-immunoprecipitation and bimolecular fluorescence complementation experiments, AZI1 interacts with MPK3 to form protein complexes in planta. Furthermore, null mutants of azil are hypersensitive to salt stress, while AZIl-overexpressing lines are markedly more tolerant. AZI1 overexpression in the mpk3 genetic background partially alleviates the salt-hypersensitive phenotype of this mutant, but functional MPK3 appears to be required for the full extent of AZIl-conferred robustness. Notably, this robustness does not come at the expense of normal development. Immunoblot and RT-PCR data point to a role of MPK3 as positive regulator of AZI1 abundance.

Plasma phospholipid transfer protein （PLTP） modulates adaptive immune functions through alternation of T helper cell polarization

Objective： Plasma phospholipid transfer protein （PLTP） is a key determinant of lipoprotein metabolism, and both animal and human studies converge to indicate that PLTP promotes atherogenesis and its thromboembolic complications. Moreover, it has recently been reported that PLTP modulates inflammation and immune responses. Although earlier studies from our group demonstrated that PLTP can modify macrophage activation, the implication of PLTP in the modulation of T-cell-mediated immune responses has never been investigated and was therefore addressed in the present study. Approach and results： In the present study, we demonstrated that PLTP deficiency in mice has a profound effect on CD4＋ ThO cell polarization, with a shift towards the anti-inflammatory Th2 phenotype under both normal and pathological conditions. In a model of contact hypersensitivity, a significantly impaired response to skin sensitization with the hapten-2,4-dinitrofluorobenzene （DNFB） was observed in PLTP-deficient mice compared to wild-type （WT） mice. Interestingly, PLTP deficiency in mice exerted no effect on the counts of total white blood cells, lymphocytes, granulocytes, or monocytes in the peripheral blood. Moreover, PLTP deficiency did not modify the amounts of CD4＋ and CD8＋ T lymphocyte subsets. However, PLTP-deficiency, associated with upregulation of the Th2 phenotype, was accompanied by a significant decrease in the production of the pro-Thl cytokine interleukin 18 by accessory cells. Conclusions： For the first time, this work reports a physiological role for PLTP in the polarization of CD4＋ T cells toward the pro-inflammatory Th I phenotype.

OsLTP47 may function in a lipid transfer relay essential for pollen wall development in rice

In plants,lipid transfer proteins(LTPs)transport pollen wall constituents from the tapetum to the exine,a process essential for pollen wall development.However,the functional cooperation of different LTPs in pollen wall development is not well understood.In this study,we have identified and characterized a grassspecific LTP gene,Os LTP47,an important regulator of pollen wall formation in rice(Oryza sativa).Os LTP47 encodes a membrane-localized LTP and in vitro lipid-binding assays confirms that Os LTP47 has lipidbinding activity.Dysfunction of Os LTP47 causes disordered lipid metabolism and defective pollen walls,leading to male sterility.Yeast two-hybrid and pull-down assays reveal that Os LTP47 physically interacts with another LTP,Os C6.These findings suggest that the plasma membrane-localized Os LTP47 may function as a mediator in a lipid transfer relay through association with cytosolic and/or locular Os C6 for pollen wall development and that various LTPs may function in a coordinated manner to transport lipid molecules during pollen wall development.

LC-MS based secondary metabolic profile of BraLTP2 overexpressing Brassica napus

BraLTP2 is an important member of lipid transfer protein family, and its molecular biology function in Brassica napus （B. napus） had been explored by prerious study. How-ever, affection of BraLTP2 on secondary metabolites is still not clear. In this study, we inves-tigated difference of leaf secondary metabolite profling between BraLTP2 overexpressing B. napus and wild type. Liquid chromatography tandem mass spectrometry （LC-MS） was utilized. Wide range of secondary metabolites was found in BraLTP2 overexpressing plants. A total of 100 secondary metabolites were determined, 42 of which had signifcant differ-ences, including favonoids, phenylpropanoids and phenolamides. These results were in accordance with signifcant increasing trichomes of overexpressing BraLTP2 plants, which might produce and store secondary metabolites. Partial least squares discriminant anal-ysis （PLS-DA） was performed to identify difference of secondary metabolites. PLS-DA score plots showed high reproducibility of each treatment. Signifcant changes were found between transformed and wild type. Permutation test validates the reliability rigorously. Fur-thermore, overexpressing of BraLTP2 led to seed germination improvement during the frst 48 h under oxidation stress. Increased oxidation resistance of transgenic B. napus was in accordance with the signifcant variations of phenylpropanoids, phenylpropanoids and phe-nolamides.This work was supported by Central Public-interest Scientifc Institution Basal Research Fund, Major Research Project of CAAS Science and National Genetically Modifed Organisms Breeding Major Projects China （2018ZX0801023B）.