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Sweet potato decays easily due to its high respiration rate and reactive oxygen species (ROS) accumulation during postharvest storage. In this study, we explored the relationship between antioxidant capacity in leaves and storage properties in different sweet potato cultivars, the tuberous roots of 10 sweet potato cultivars were used as the experimental materials to analyze the storage property during storage at 11-15°C. According to the decay percentage after 290 days of storage, Xu 32 was defined as a storage-tolerant cultivar (rot percentage less than 25%); Xu 55-2, Z 15-1, Shangshu 19, Yushu, and Zhezi 3 as above-moderate storage-tolerant cultivars (rot percentage ranging from 25 to 50%); Sushu 16, Yanshu 5, and Hanzi as medium-storable cultivars (rot percentage 50-75%); and Yan 25 as a storage-sensitive cultivar (rot percentage greater than 75%). Meanwhile, analysis of the α-amylase activity in root tubers of the 10 sweet potato cultivars during storage indicated that α-amylase activity was lowest in the storage-tolerant cultivar Xu 32 and highest in the storage-sensitive cultivar Yan 25. Evaluation of antioxidant enzyme activities and ROS content in the leaves of these 10 cultivars demonstrated that cultivar Xu 32, which showed the best storage property, had higher antioxidant enzyme activity [superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD)] but lower lipoxygenase (LOX) activity, hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA) contents, and superoxide anion radical (O 2 ⋅ - ) production rates compared with those of the storage-sensitive cultivar Yan 25 and the medium-storability cultivars Hanzi, Yanshu 5, and Sushu 16. Additionally, principal component analysis (PCA) suggested that sweet potato cultivars with different storage properties were clustered separately. Correlation and heat map analysis further indicated that CAT, APX, POD, and SOD activities were negatively correlated with α-amylase activity, while LOX activity and MDA and H 2 O 2 contents were negatively correlated with the storage property of sweet potato. Combined, our findings revealed that storage property is highly correlated with antioxidant capacity in sweet potato leaves and negatively correlated with α-amylase activity in tuberous roots, which provides a convenient means for the screening of storage-tolerant sweet potato cultivars., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Song, Zhou, Zhao, Tang, Li, Han, Chen, Hu, Yao and Zhang.)

Hydrogen sulfide (H 2 S) could act as a versatile signaling molecule in delaying fruit ripening and senescence. Ethylene (C 2 H 4 ) also plays a key role in climacteric fruit ripening, but little attention has been given to its interaction with H 2 S in modulating fruit ripening and senescence. To study the role of H 2 S treatment on the fruit quality and nutrient metabolism, tomato fruits at white mature stage were treated with ethylene and ethylene plus H 2 S. By comparing to C 2 H 4 treatment, we found that additional H 2 S significantly delayed the color change of tomato fruit, and maintained higher chlorophyll and lower flavonoids during storage. Moreover, H 2 S could inhibit the activity of protease, maintained higher levels of nutritional-related metabolites, such as anthocyanin, starch, soluble protein, ascorbic acid by comparing to C 2 H 4 treatment. Gene expression analysis showed that additional H 2 S attenuated the expression of beta-amylase encoding gene BAM3 , UDP-glycosyltransferase encoding genes, ethylene-responsive transcription factor ERF003 and DOF22 . Furthermore, principal component analysis suggested that starch, titratable acids, and ascorbic acid were important factors for affecting the tomato storage quality, and the correlation analysis further showed that H 2 S affected pigments metabolism and the transformation of macromolecular to small molecular metabolites. These results showed that additional H 2 S could maintain the better appearance and nutritional quality than C 2 H 4 treatment alone, and prolong the storage period of post-harvest tomato fruits., (Copyright © 2020 Yao, Li, Sun, Tang, Huang, Yang, Huang, Hu, Jin, Hu and Zhang.)

Hydrogen sulfide (H 2 S) has been postulated to be the third gasotransmitter in both animals and plants after nitric oxide (NO) and carbon monoxide (CO). In this review, the physiological roles of H 2 S in plant growth, development and responses to biotic, and abiotic stresses are summarized. The enzymes which generate H 2 S are subjected to tight regulation to produce H 2 S when needed, contributing to delicate responses of H 2 S to environmental stimuli. H 2 S occupies a central position in plant sulfur metabolism as it is the link of inorganic sulfur to the first organic sulfur-containing compound cysteine which is the starting point for the synthesis of methionine, coenzyme A, vitamins, etc. In sulfur assimilation, adenosine 5'-phosphosulfate reductase (APR) is the rate-limiting enzyme with the greatest control over the pathway and probably the generation of H 2 S which is an essential component in this process. APR is an evolutionarily conserved protein among plants, and two conserved domains PAPS_reductase and Thioredoxin are found in APR. Sulfate reduction including the APR-catalyzing step is carried out in chloroplasts. APR, the key enzyme in sulfur assimilation, is mainly regulated at transcription level by transcription factors in response to sulfur availability and environmental stimuli. The cis -acting elements in the promoter region of all the three APR genes in Solanum lycopersicum suggest that multiple factors such as sulfur starvation, cytokinins, CO 2 , and pathogens may regulate the expression of SlAPRs . In conclusion, as a critical enzyme in regulating sulfur assimilation, APR is probably critical for H 2 S generation during plants' response to diverse environmental factors.