The ripening of papaya is a physiological and metabolic process associated with accumulation of carotenoids, alternation of flesh color and flavor, which depending on genotype and external factors such as light and hormone. Transcription factors regulating carotenoid biosynthesis have not been analyzed during papaya fruit ripening. RNA-Seq experiments were implemented using different ripening stages of papaya fruit from two papaya varieties. Cis -elements in lycopene β-cyclase genes ( CpCYC-B and CpLCY-B ) were identified, and followed by genome-wide analysis to identify transcription factors binding to these cis -elements, resulting in the identification of CpbHLH1 and CpbHLH2 , two bHLH genes. The expressions of CpbHLH1/2 were changed during fruit development, coupled with transcript increase of carotenoid biosynthesis-related genes including CpCYC-B , CpLCY-B , CpPDS2 , CpZDS , CpLCY-E , and CpCHY-B . Yeast one-hybrid (Y1H) and transient expression assay revealed that CpbHLH1/2 could bind to the promoters of CpCYC-B and CpLCY-B , and regulate their transcriptions. In response to strong light, the results of elevated expression of carotenoid biosynthesis-related genes and the changed expression of CpbHLH1/2 indicated that CpbHLH1/2 were involved in light-mediated mechanisms of regulating critical genes in the carotenoid biosynthesis pathway. Collectively, our findings demonstrated several TF family members participating in the regulation of carotenoid genes and proved that CpbHLH1 and CpbHLH2 individually regulated the transcription of lycopene β-cyclase genes ( CpCYC-B and CpLCY-B ). This study yielded novel findings on regulatory mechanism of carotenoid biosynthesis during papaya fruit ripening.

No abstract

Since a large number of contaminants are detected in source waters (SWs) and tap waters (TWs), it is important to perform a comprehensive effect evaluation and key contributor identification. A reduced human transcriptome (RHT)-based effect-directed analysis, which consisted of a concentrationdependent RHT to reveal the comprehensive effects and noteworthy pathways and systematic identification of key contributors based on the interactions between compounds and pathway effects, was developed and applied to typical SWs and TWs along the Yangtze River. By RHT, 42% more differentially expressed genes and 33% more pathways were identified in the middle and lower reaches, indicating heavier pollution. Hormone and immune pathways were prioritized based on the detection frequency, sensitivity, and removal efficiency, among which the estrogen receptor pathway was the most noteworthy. Consistent with RHT, estrogenic effects were widespread along the Yangtze River based on in vitro evaluations. Furthermore, 38 of 100 targets, 39 pathway-related suspects, and 16 estrogenic nontargets were systematically identified. Among them, diethylstilbestrol was the dominant contributor, with the estradiol equivalent (EEQ) significantly correlated with EEQ water . In addition, zearalenone and niclosamide explained up to 54% of the EEQ water . The RHT-based EDA method could support the effect evaluation, contributor identification, and risk management of micropolluted waters.

In this study, nanoscale zero-valent iron (NZVI) was synthesized by conventional liquid-phase chemical reduction methods without a support material and then characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of NZVI particles on phosphate removal from aqueous solutions was examined. The results showed that the phosphate removal efficiency increased from 34.49% to 87.01% as the dosage of nanoscale iron particles increased from 100 to 600 mg L(-1) with an initial phosphate concentration of 10 mg L(-1), and the phosphate removal efficiency decreased from 72.89% to 51.39% as the initial phosphate concentration increased from 10 to 90 mg L(-1), with 400 mg L(-1) NZVI. Phosphate removal efficiencies of 99.41% and 95.09% were achieved at pH values of 2 and 4, respectively, with an initial phosphate concentration of 20 mg L(-1) and 400mg L(-1) NZVI. The use of NZVI particles synthesized in a carboxymethyl cellulose (CMC)-water solution significantly enhanced phosphate removal from an aqueous solution compared with the use of NZVI synthesized in an ethanol-water solution. NZVI particles achieved 71.34% phosphate removal, which was remarkably higher than that of microscale zero-valent iron (MZVI) particles (16.35%) with 10 mg L(-1) of phosphate and 400mg L(-1) iron. Based on the removal mechanism analysis performed in this study, we recommend that phosphate removal be accomplished by simultaneous adsorption and chemical precipitation. The XRD patterns of the NZVI before and after the reactions indicated the formation of crystalline vivianite (Fe3(PO4)2 x 8H2O) during the procedure.