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Understanding the molecular responses of plant roots to the challenging environment contributes to engineering plants with improved stress tolerance. However, little has been done to understand rice (Oryza sativa L.) roots response to the toxic concentration of zinc (Zn) at the proteomic level. This study explored proteomic responses of young rice roots 5–6 days after sowing to 765 μM of Zn in a hydroponic set-up after 4-day exposure. Dye staining method and spectrophotometry were chosen for physiological response investigations. ICP-MS was used to determine metal content in rice seedlings. Two-dimensional gel electrophoresis was used for the proteomic study of root tissue. Elevated Zn reduced Mg translocation to the shoots and Mn uptake, decreased plant growth, and increased cell death of roots. Zn stimulated the biosynthesis of glutathione but decreased ROS and malondialdehyde levels. In total, 42 Zn-responsive proteins were identified. Proteins involved in redox regulation, defense response, sulfur metabolism, and proteolysis were induced, while those of energy production and cell wall biogenesis were decreased. Roots of O. sativa seedlings could tolerate certain Zn excess (765 μM Zn for 4 days) by stimulating nutrient recycling and glycolysis, and production of defensive metabolites and proteins to maintain ion and redox homeostasis. Besides, adenosylhomocysteinase (AHCY) down-regulation may contribute to balanced transmethylations, and methionine salvage pathway appears important for the adaptation to Zn. Our results provide some new insight into a complex metabolic response of rice roots to Zn stress, which is related to both stress and defense mechanisms.

Background and aims Kandelia obovata, a dominant mangrove species in China, produces complex buttress roots and prop roots in intertidal wetlands where high quantities of nitric oxide (NO) are produced by reducing sediments. NO, a key signaling molecule, participates in an array of plant physiological and developmental processes. However, it is unclear whether NO functions in K. obovata root system establishment. Methods Here, we used a transcriptomic approach to investigate the potential role of NO in the regulation of K. obovata lateral root development and growth. Transcript profiles and bioinformatics analyses were used to characterize potential regulatory mechanisms. Results NO enhanced K. obovata lateral root development and growth in a dose-dependent manner. RNA-seq analysis identified 1,593 differentially expressed genes (DEGs), of which 646 and 947 were up- and down-regulated in roots treated with NO donor. Functional annotation analysis demonstrated that the starch and sucrose pathway was significantly induced in response to NO. A suite of DEGs involved in hormone signal transduction and cell wall metabolism was also differentially regulated by NO. Taken together, our results suggest that a complex interaction between energy metabolism, multiple hormone signaling pathways, and cell wall biosynthesis is required for the NO regulation on lateral root development and growth in mangrove plant K. obovata. Conclusion NO appears to contribute to the formation of the unique root system of mangrove plants.

Mangrove ecosystems are an important component of “blue carbon”. However, it is not clear whether the stems play roles in the CH4 budget of mangrove ecosystems. This study investigated the CH4 emission from mangrove stems and its potential driving factors. We set up six sample plots in the Zhangjiang Estuary National Mangrove Nature Reserve, where Kandelia obovata, Avicennia marina and Aegiceras corniculata are the main mangrove tree species. Soil properties such as total carbon content, redox potential and salinity were determined in each plot. The dynamic chamber method was used to measure mangrove stems and soil CH4 fluxes. Combined field survey results with Principal Component Analysis (PCA) of soil properties, we divided the six plots into two sites (S1 and S2) to perform statistical analyses of stem CH4 fluxes. Then the CH4 fluxes from mangrove tree stems and soil were further scaled up to the ecosystem level through the mapping model. Under different backgrounds of soil properties, salinity and microbial biomass carbon were the main factors modified soil CH4 fluxes in the two sites, and further affected the stem CH4 fluxes of mangroves. The soil of both sites are sources of CH4, and the soil CH4 emission of S2 was about twice higher than that of S1. Results of upscaling model showed that mangrove stems in S1 were CH4 sinks with −105.65 g d−1. But stems in S2 were CH4 sources around 1448.24 g d−1. Taken together, our results suggested that CH4 emission from mangrove soils closely depends on soils properties. And mangrove stems were found to act as both CH4 sources and CH4 sinks depend on soil CH4 production. Therefore, when calculating the CH4 budget of the mangrove ecosystem, the contribution of mangrove plant stems cannot be ignored.

A series of nine CoII, CuII, and CdII mixed-ligand coordination complexes with a 3,3′-dipyridyl connector 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole (3-bpt) have been achieved, by changing the incorporated benzenedicarboxylic co-ligands from isophthalic acid (H2ip) to its 5-substituted derivatives 5-nitroisophthalic acid (–NO2, H2nip) and trimesic acid (–COOH, H3tma). All compounds have been structurally determined by the X-ray diffraction technique. It is indicated that most of them are coordination polymers, with the ligands of benzenecarboxylic acids being doubly deprotonated to compensate the charge and bridge the metal ions, except for a monomeric ion-pair product [Co(3-bpt)2(H2O)4]·(H2tma)2·(H2O)2 (1c). These polymers display a variety of coordination frameworks, such as 1-D double-strand chain, 2-D layer with (4,4) topology, 2-D double layer, 2-D layer with (6,3) topology and 1-D molecular ladder etc. The results evidently reveal the profound substituent effect of the R-isophthalate building blocks on engineering such coordination arrays, in virtue of the versatility of 3-bpt with diversiform configurations and binding fashions. Nevertheless, the choice of metal ion is also significant in the structural assembly, and the low-dimensional coordination networks are further extended to diverse 3-D supramolecular crystalline lattices via noncovalent interactions especially hydrogen bonding. Solid-state properties such as thermal stability and fluorescence have also been investigated.

Assemblies of an angular dipyridyl ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) with a series of metal perchlorate afford five new supramolecular complexes with the general formula of [M(4-bpo)2(H2O)4] · (4-bpo)2 · (anion) · (solvent), in which M = MnII for 1, FeII for 2, CoII for 3, ZnII for 4, and FeIII for 5. Although similar molecular structures and compositions are found for these mononuclear complexes, they display two types of supramolecular lattices. Complexes 1, 4 and 5 similarly crystallize in space group P2/n or P2/c. The complex cations, free 4-bpo and lattice water are linked to generate 2D layered frameworks with the aid of hydrogen bonding, and the counter anions are located within and between (also methanol in 5) these 2D arrays. However, complexes 2 and 3 are isostructural in space group P 1 ¯ . Two types of alternate 2D layers consisting of complex cations and free 4-bpo components, respectively, are observed with the anions and lattice water locating between them. These motifs are interlinked by complicated hydrogen-bonding to form a 3D intercalated network. Moreover, when Co(NO3)2 is used instead of Co(ClO4)2 in the assembly of 3, a 1D polymeric chain complex {[Co(4-bpo)(H2O)2(NO3)2](H2O)3}n (6) is generated. These results indicate that the choice of metal ion and anion exerts a significant influence on governing the target complexes. A comparison of the structural features for all metal perchlorate complexes with 4-bpo is also briefly discussed.

The combination of biphenyl-4,4'-dicarboxylic acid (H2bpa) and the bent dipyridyl base 2,5-di-4-pyridyl-1,3,4-oxadiazole (4-bpo) in a 1:1 molar ratio leads to the formation of the molecular co-crystal (H2bpa).(4-bpo) or C14H10O4.C12H8N4O. The asymmetric unit contains one-half of an H2bpa unit lying across a centre of inversion and one-half of a 4-bpo molecule lying across a twofold rotation axis. Intermolecular O-H...N interactions connect the acid and base molecules to form a one-dimensional zigzag chain. Through further weak C-H...O hydrogen bonds between adjacent chains, a two-dimensional sheet-like supramolecular network is afforded. As an extended analogue of terephthalic acid (H2tp), the backbone geometry of H2bpa has an evident influence on the hydrogen-bonding pattern of the title co-crystal compared with that of (H2tp).(4-bpo).