Hydrogen peroxide (H2O2) is relatively stable among ROS (reactive oxygen species) and could act as a signal in plant cells. In the present work, detached tomato leaves were treated with exogenous H2O2 at 10 mmol/L for 8 h to study the mechanism of how H2O2 regulates leaf senescence. The data indicated that H2O2 treatment significantly accelerated the degradation of chlorophyll and led to the upregulation of the expression of leaf senescence-related genes (NYC1, PAO, PPH, SGR1, SAG12 and SAG15) during leaf senescence. H2O2 treatment also induced the accumulation of H2O2 and malondialdehyde (MDA), decreased POD and SOD enzyme activities and inhibited H2S production by reducing the expression of LCD1/2 and DCD1/2. A correlation analysis indicated that H2O2 was significantly and negatively correlated with chlorophyll, the expression of leaf senescence−related genes, and LCD1/2 and DCD1/2. The principal component analysis (PCA) results show that H2S showed the highest load value followed by O2•−, H2O2, DCD1, SAG15, etc. Therefore, these findings provide a basis for studying the role of H2O2 in regulating detached tomato leaf senescence and demonstrated that H2O2 plays a positive role in the senescence of detached leaves by repressing antioxidant enzymes and H2S production.

Hydrogen sulfide(H2S)is involved in multiple processes during plant growth and development.D-cysteine desulfhydrase(DCD)can produce H2S with D-cysteine as the substrate;however,the potential developmental roles of DCD have not been explored during the tomato lifecycle.In the present study,SlDCD2 showed increasing expression during fruit ripening.Compared with the control fruits,the silencing of SlDCD2 by pTRV2-SlDCD2 accelerated fruit ripening.A SlDCD2 gene-edited mutant was constructed by CRISPR/Cas9 transformation,and the mutant exhibited accelerated fruit ripening,decreased H2S release,higher total cysteine and ethylene contents,enhanced chlorophyll degradation and increased carotenoid accumulation.Additionally,the expression of multiple ripening-related genes,including NYC1,PAO,SGR1,PDS,PSY1,ACO1,ACS2,E4,CEL2,and EXP was enhanced during the dcd2 mutant tomato fruit ripening.Compared with the wild-type fruits,SlDCD2 mutation induced H2O2 and malondialdehyde(MDA)accumulation in fruits,which led to an imbalance in reactive oxygen species(ROS)metabolism.A correlation analysis indicated that H2O2 content was strongly positively correlated with carotenoids content,ethylene content and ripening-related gene expression and negatively correlated with the chlorophyll content.Additionally,the dcd2 mutant showed earlier leaf senescence,which maybe due to disturbed ROS homeostasis.In short,our findings show that SlDCD2 is involved in H2S generation and that the reduction in endogenous H2S production in the dcd2 mutant causes accelerated fruit ripening and premature leaf senescence.Additionally,decreased H2S in the dcd2 mutant causes excessive H2O2 accumulation and increased ethylene release,suggesting a role of H2S and SlDCD2 in modulating ROS homeostasis and ethylene biosynthesis.

Tomato is one of the most popular horticultural crops, and many commercial tomato cultivars are particularly susceptible to Botrytis cinerea. Hydrogen sulfide (H2S) is an important gaseous molecule in various plant stress responses. In this study, it was found that endogenous H2S increases in tomato leaves in response to B. cinerea infection, along with a 3.8-fold increase in gene expression of DCD1 which encodes a H2S-generating enzyme D-cysteine desulfhydrase 1 in tomato at 3 DPI. Then we investigated the role of DCD1 in resistance of tomato leaves and fruits to B. cinerea. The mutation of DCD1 by CRIPSR/Cas9 greatly reduced the resistance of tomato leaves and breaker and red fruits to B. cinerea accompanied with increased reactive oxygen species (ROS) especially hydrogen peroxide (H2O2) and malondialdehyde (MDA) content increased by 1.2 and 1.4 times respectively at 5 DPI of leaves. Further investigation showed that DCD1 mutation caused decreased activity of antioxidative enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) in both leaves and fruits, in particular, CAT activity in dcd1 mutant was 25.0 % and 41.7 % of that in WT at leaves and red fruits at 5 DPI. DCD1 mutation also caused decreased expression of defense-related genes PAL (encoding phenylalanine ammonia-lyase) and PUB24, and their expression in the dcd1 red fruit is approximately 1.3 and 1.8 times higher than in wild-type red fruit at 5 DPI, respectively. Thus, the work emphasizes the positive role of DCD1 and H2S in plant responses to necrotrophic fungal pathogens. In addition, the work provides strong evidence that fruit at ripened stage is more susceptible to B. cinerea infection compared with green fruit, suggesting that senescence of plant tissues is more favorable to B. cinerea infection.

Dielectric materials with both high recoverable energy-storage density Wrec and efficiency eta have attracted a lot of attention in recent years. Permittivity plays a crucial role in simultaneously achieving high polarization strength and large applied electric fields for any kinds of dielectric materials, among which antiferroelectric ceramics exhibit giant potentials in energy storage. Adjustment of permittivity has seemed to be more in linear dielectrics, but much less cared about in polar dielectrics so far for high-power energy-storage applications. In this work, a novel lead-free solid solution of (1-x)(Bi0.5Na0.5)TiO3-xKNbO3 was reported to show excellent comprehensive energy-storage performances of Wrec of -5.2 J/cm(3), large eta of-88%, fast discharge rate of t(0.9) < 200 ns and outstanding temperature and frequency stability at x = 0.16. The X-ray, Raman spectra and scanning electron microscopy and so on demonstrate that it was basically ascribed to the formation of relaxor antiferroelectric phases with temperature-stable dielectric response and expanded linear polarization response, as well as enhanced dielectric breakdown strength induced by sub-micron grains. Particularly, selection of an appropriately medium permittivity value of about one thousand enables the studied AFE composition bring its superiority into full play in energy-storage properties, as demonstrated by a comparison between Wrecvalues of most previously-reported lead-free ceramics and theoretically predicted ones for linear dielectrics. These findings achieved in current work would provide an important guidance for compositionally designing high-performance energy-storage dielectrics in terms of modifying dielectric properties and polarization responses, particularly for relaxor antiferroelectrics with linear-like characteristics.