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Aims and methods The molecular mechanisms and signal transduction pathways of hydrogen sulfide (H 2 S) in plant biology are still unclear. Here, by using pharmacological and biochemical approaches, we report that H 2 S promotes germination and alleviates salinity damage involving nitric oxide (NO) pathway. Results Upon 100 mM NaCl treatment, both H 2 S donor sodium hydrosulfide (NaHS) and NO donor sodium nitroprusside (SNP) at 100 μM could significantly attenuate the inhibition of alfalfa (Medicago sativa) seed germination and thereafter seedling growth inhibition. Meanwhile, the ratio of potassium (K) to sodium (Na) in the root parts was increased.Total, isozymatic activities or corresponding transcripts of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), or ascorbate peroxidase (APX) were activated differentially, thus resulting in the alleviation of oxidative damage. The above protective roles of NaHS might be related to the induction of endogenous NO, because the addition of the specific scavenger of NO 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO) reversed above effects. Meanwhile, NaHStriggered NO production was confirmed. Conclusions Our observations indicate that H 2 S enhances plant responses against salinity stress by reducing oxidative damage, which might have a possible interaction with NO.

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Novel semisynthetic vancomycin derivatives with antibacterial activity against vancomycin-resistant S. aureus (VRSA) were prepared. Replacement of Cl groups of vancomycin by Suzuki-Miyaura cross-coupling reaction, which gave the title compounds, is described for the first time. Introduction of a carbon substituent at the amino acid residue 2 of vancomycin led to an enhancement of antibacterial activity against vancomycin-resistant strains, whereas the additional introduction at the amino acid residue 6 resulted in a reduction in activity even against vancomycin-susceptible strains.

Pretreatment of lower H 2 O 2 doses (0.05, 0.5 and 5 mM) for 24 h was able to dose-dependently attenuate lipid peroxidation in wheat seedling leaves mediated by further oxidative damage elicited by higher dose of H 2 O 2 (150 mM) for 6 h, with 0.5 mM H 2 O 2 being the most effective concentrations. Further results illustrated that 0.5 mM H 2 O 2 pretreatment triggered the biphasic production of H 2 O 2 during a 24 h period. We also noticed that only peak I (0.25 h) rather than peak II (4 h) was approximately consistent with the enhancement of heme oxygenase (HO) activity, HO-1 gene expression. Meanwhile, enhanced superoxide dismutase (SOD) activity, Mn-SOD and Cu,Zn-SOD transcripts might be a potential source of peak I of endogenous H 2 O 2 . Further results confirmed that 0.5 mM H 2 O 2 treatment for 0.5 h was able to upregulate HO gene expression, which was detected by enzyme activity determination, semi-quantitative reverse transcription-polymerase chain reaction and western blotting. Meanwhile, the application of N,N'-dimethylthiourea, a trap for endogenous H 2 O 2 , not only blocked the upregulation of HO, but also reversed the corresponding oxidation attenuation. Together, the above results suggest that endogenous H 2 O 2 production (peak I) plays a positive role in the induction of HO by enhancing its mRNA level and protein expression, thus leading to the acclimation to oxidative stress.Key words: acclimation to oxidative stress; endogenous hydrogen peroxide; heme oxygenase; signal transduction; Triticum.Chen XY, Ding X, Xu S, Wang R, Xuan W, Cao ZY, Chen J, Wu HH, Ye MB, Shen WB (2009). Endogenous hydrogen peroxide plays a positive role in the upregulation of heme oxygenase and acclimation to oxidative stress in wheat seedling leaves. J. Integr. Plant Biol. 51(10), 951-960. Available online at www.jipb.net Hydrogen peroxide (H 2 O 2 ), as well as the other reactive oxygen species (ROS), generated in a variety of biotic and abiotic stimuli, was viewed as a toxic molecule to plant cellular Received 16 Dec. 2008 Accepted 7 Jul. 2009 Supported by the fund for Creative Experimental Project of Undergraduate Students in Jiangsu Province of China (96), the program for New Century Excellent Talents in University (NCET-07-0441), the Natural Science Foundation of China (30671248), and the grant obtained from the 111 Project of China (B07030).* Author for correspondence. structures and some macromolecules such as lipids, proteins and nucleic acids (Halliwell 1981). However, much evidence has recently emerged that H 2 O 2 also functions as an important signal molecule mediating the phenomena of acclimation and cross-tolerance, in which previous exposure to one stress can induce tolerance of subsequent exposure to the same or different stresses (Neill et al. 2002a(Neill et al. , 2002b. However, the mechanism(s) by which H 2 O 2 mediated acclimation and crosstolerance is currently not fully understood in plants.Heme oxygenase (HO, EC 1.14.99.3), the rate-limiting step in heme degradation to carbon monoxide (...

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In this paper, the regulatory role of exogenous carbon monoxide (CO) during the generation and development of adventitious roots in mung bean (Phaseolus radiatus L. cv. Mingguang) hypocotyl cuttings was surveyed. The results indicated that, like nitric oxide (NO), CO donor Hematin induced adventitious rooting in dose-and time-dependent manners. These responses were also proven by the addition of gaseous CO aqueous solution with different concentrations. Additionally, the above CO-mediated effect was differently reversed when CO scavenger hemoglobin (Hb), CO specific synthetic inhibitor ZnPPIX, the auxin transport inhibitor NPA and nitric oxide synthase (NOS) inhibitor L-NAME were added with Hematin, respectively. Furthermore, after being treated with CO for 36 h, NO fluorescence was significantly enhanced and mainly distributed in the zone of vascular bundles whereas the specific NO scavenger cPTIO significantly inhibited NO fluorescence induced by CO, indicating that CO induces adventitious rooting of hypocotyl cuttings from mung bean seedling probably mediated by NO/NOS pathway.Carbon monoxide (CO) and nitric oxide (NO), two diatomic gaseous molecules, belong to mid-valent oxide of carbon and nitrogen element, respectively. In fact, CO shares many physical and chemical properties with NO. Recent studies showed that formation of CO in animal tissues is mainly catalyzed by heme oxygenase (HO, EC 1.14.99.3) from heme. Also, the regulation of respiration, cardiovascular, nerve and immune systems by CO was mainly mediated by NO signal, and cyclic GMP (cGMP) was by far the commonest second messenger [1][2][3][4] .While in plants, although several laboratories have reported the direct emission of CO by living green plants when exposed to sunlight or during seedling growth since 1959 [5,6] , little was known about the exact mechanism of biosynthesis and even biological roles of CO in plants, and HO was also thought of as potential sources of CO in plant cells [7] . Meanwhile, endogenous NO in plants is produced mainly by nitric oxide synthase (NOS) or nitrate reductase (NR), and was further proven to participate in many physiological processes in plants, such as plant defense responses, seed germination, root organogensis and stress tolerance [8][9][10][11] . In 2002, Pagnussat et al. [12] first discovered that NO donor sodium nitroprusside (SNP) promoted the adventitious root formation in cucumber seedlings, a similar response to that obtained with IAA. More recently, She and Huang [13,14] also found that SNP induced the generation and development of adventitious roots in mung bean hypocotyl cuttings. It was well known that the formation of adventitious roots is an important issue in the research of developmental biology. Given the similar properties of both NO and CO, does CO exhibit the same regulatory role in the process of adventitious rooting? In this work, we discovered that CO induced the adventitious root generation in mung bean hypocotyl cuttings. Furthermore, through pharmacological and surgical approaches c...