SUMMARYSpermidine (Spd) has been correlated with various physiological and developmental processes in plants, including pollen tube growth. In this work, we show that Spd induces an increase in the cytosolic Ca 2+ concentration that accompanies pollen tube growth. Using the whole-cell patch clamp and outside-out singlechannel patch clamp configurations, we show that exogenous Spd induces a hyperpolarization-activated Ca This messenger is hydrogen peroxide (H 2 O 2 ), and is generated during Spd oxidation, a reaction mediated by polyamine oxidase (PAO). These reactive oxygen species trigger the opening of the hyperpolarizationactivated Ca 2+ -permeable channels in pollen. To provide further evidence that PAO is in fact responsible for the effect of Spd on the Ca 2+ -permeable channels, two Arabidopsis mutants lacking expression of the peroxisomalencoding AtPAO3 gene, were isolated and characterized. Pollen from these mutants was unable to induce the opening of the Ca 2+ -permeable channels in the presence of Spd, resulting in reduced pollen tube growth and seed number. However, a high Spd concentration triggers a Ca 2+ influx beyond the optimal, which has a deleterious effect. These findings strongly suggest that the Spd-derived H 2 O 2 signals Ca 2+ influx, thereby regulating pollen tube growth.

The exploitation of gas therapy platforms holds great promise as a “green” approach for selective cancer therapy, however, it is often associated with some challenges, such as uncontrolled or insufficient gas generation and unclear therapeutic mechanisms. In this work, a gas therapy approach based on near-infrared (NIR) light-triggered sulfur dioxide (SO2) generation was developed, and the therapeutic mechanism as well as in vivo antitumor therapeutic efficacy was demonstrated. A SO2 prodrug-loaded rattle-structured upconversion@silica nanoparticles (RUCSNs) was constructed to enable high loading capacity without obvious leakage and to convert NIR light into ultraviolet light so as to activate the prodrug for SO2 generation. In addition, SO2 prodrug-loaded RUCSNs showed high cell uptake, good biocompatibility, intracellular tracking ability, and high NIR light-triggered cytotoxicity. Furthermore, the cytotoxic SO2 was found to induce cell apoptosis accompanied by the increase of intracellular reactive oxygen species levels and the damage of nuclear DNA. Moreover, efficient inhibition of tumor growth was achieved, associated with significantly prolonged survival of mice. Such NIR light-triggered SO2 therapy may provide an effective strategy to stimulate further development of synergistic cancer therapy platforms.

BackgroundThe leaf is an important plant organ, and how it will respond to future global warming is a question that remains unanswered. The effects of experimental warming on leaf photosynthesis and respiration acclimation has been well studied so far, but relatively little information exists on the structural and biochemical responses to warming. However, such information is very important to better understand the plant responses to global warming. Therefore, we grew Arabidopsis thaliana at the three day/night temperatures of 23/18°C (ambient temperature), 25.5/20.5°C (elevated by 2.5°C) and 28/23°C (elevated by 5°C) to simulate the middle and the upper projected warming expected within the 21st century for this purpose.ResultsThe 28/23°C treatment significantly reduced the life span, total biomass and total weight of seeds compared with the other two temperatures. Among the three temperature regimes, the concentrations of starch, chlorophyll, and proline were the lowest at 28/23°C, whereas the total weight of seeds, concentrations of chlorophyll and proline, stomatal density (SD), stomatal conductance (gs), net CO2 assimilation rate (A) and transpiration rate (E) were the highest at 25.5/20.5°C. Furthermore, the number of chloroplasts per cell and mitochondrial size were highest at 25.5/20.5°C and lowest at 28/23°C.ConclusionsThe conditions whereby the temperature was increased by 2.5°C were advantageous for Arabidopsis. However, a rise of 5°C produced negative effects, suggesting that lower levels of warming may benefit plants, especially those which belong to the same functional group as Arabidopsis, whereas higher levels of warming may produce negative affects. In addition, the increase in A under moderately warm conditions may be attributed to the increase in SD, chlorophyll content, and number of chloroplasts. Furthermore, starch accumulation in chloroplasts may be the main factor influencing chloroplast ultrastructure, and elevated temperature regulates plant respiration by probably affecting mitochondrial size. Finally, high SOD and CAT activities may enable plants grown at elevated temperatures to exhibit relatively high tolerance to temperature stress, thus alleviating the harmful effects of superoxide anion radicals and hydrogen peroxide.

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The cyclic nucleotide-gated channel (CNGC) family is involved in the uptake of various cations, such as Ca(2+), to regulate plant growth and respond to biotic and abiotic stresses. However, there is far less information about this family in woody plants such as pear. Here, we provided a genome-wide identification and analysis of the CNGC gene family in pear. Phylogenetic analysis showed that the 21 pear CNGC genes could be divided into five groups (I, II, III, IVA and IVB). The majority of gene duplications in pear appeared to have been caused by segmental duplication and occurred 32.94-39.14 million years ago. Evolutionary analysis showed that positive selection had driven the evolution of pear CNGCs. Motif analyses showed that Group I CNGCs generally contained 26 motifs, which was the greatest number of motifs in all CNGC groups. Among these, eight motifs were shared by each group, suggesting that these domains play a conservative role in CNGC activity. Tissue-specific expression analysis indicated that functional diversification of the duplicated CNGC genes was a major feature of long-term evolution. Our results also suggested that the P-S6 and PBC & hinge domains had co-evolved during the evolution. These results provide valuable information to increase our understanding of the function, evolution and expression analyses of the CNGC gene family in higher plants.

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