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The degradation of chlorophyll during fruit development is essential to reveal a more 'ripe' color that signals readiness to wild dispersers of seeds and the human consumer. Here, comparative biochemical analysis of developing fruit of Actinidia deliciosa cv. Xuxiang ('XX', green-fleshed) and Actinidia chinensis cv. Jinshi No.1 ('JS', yellow-fleshed) indicated that variation in chlorophyll content is the major contributor to differences in flesh color. Four differentially expressed candidate genes were identified: the down-regulated genes AcCRD1 and AcPOR1 involved in chlorophyll biosynthesis, and the up-regulated genes AcSGR1 and AcSGR2 driving chlorophyll degradation. Prochlorophyllide and chlorophyllide, the metabolites produced by AcCRD1 and AcPOR1, progressively reduced in 'JS', but not in 'XX', indicating that chlorophyll biosynthesis was less active in yellow-fleshed fruit. AcSGR1 and AcSGR2 were verified to be involved in chlorophyll degradation, using both transient expression in tobacco and stable overexpression in kiwifruit. Furthermore, a homeobox-leucine zipper (HD-Zip II), AcHZP45 , showed significantly increased expression during 'JS' fruit ripening, which led to both repressed expression of AcCRD1 and AcPOR1 and activated expression of AcSGR1 and AcSGR2. Collectively, the present study indicated that different dynamics of chlorophyll biosynthesis and degradation coordinate the changes in chlorophyll content in kiwifruit flesh, which are orchestrated by the key transcription factor AcHZP45. [ABSTRACT FROM AUTHOR]

Dictamnine (DTN), a furoquinoline alkaloid isolated from Dictamni Cortex, is responsible for the liver injury caused by Dictamni Cortex and the preparations. Discovering new biomarkers with high specificity and sensitivity for diagnosis and tracing the source of DTN‐induced liver injury is urgently needed. Considering that metabolic activation of DTN has been suggested as a primary trigger initiating hepatotoxicity, the present study aimed to investigate the bio‐activation process of DTN in vitro and in mice and to explore whether the adducts could be developed as exposure biomarkers. When trapping with N‐acetyl‐cysteine (NAC) and glutathione (GSH) in mouse liver microsomes and CYP3A4 overexpressed L02 cells, two isomers of DTN‐NAC adducts were detected in both systems and one DTN‐GSH adduct was found in mouse liver microsomes. As expected, one DTN‐NAC adduct was also found in plasma and bile of mice with liver injury after DTN exposure. Moreover, mouse liver microsomes were used to simulate the conjugation of serum albumin with metabolically activated DTN. The sole modified peptide 25DAHKSEVAHR34 was found, and the oxidative metabolites of DTN might bind to the side chain amino of albumin at Arg34. The above findings not only provided confirmative evidence that DTN was metabolically activated to induce liver injury but also suggested that the adducts had the potential to be developed as exposure biomarkers of DTN‐induced liver injury. The furan ring of DTN was bioactivated to the intermediate and to yield adducts. In the study, DTN was trapped with NAC or GSH in vitro, and NAC and GSH adducts were detected. In CYP3A4 overexpressed L02 cells, only a DTN‐NAC adduct was found. Only a DTN‐NAC adduct was found in plasma and bile of mice with liver injury. One DTN‐albumin adduct was found in vitro, and the binding site was at Arg34. [ABSTRACT FROM AUTHOR]