Carotenoids exert multifaceted roles to plants and are critically important to humans. Phytoene synthase (PSY) is a major ratelimiting enzyme in the carotenoid biosynthetic pathway. PSY in plants is normally found as a small enzyme family with up to three members. However, knowledge of PSY isoforms in relation to their respective enzyme activities and amino acid residues that are important for PSY activity is limited. In this study, we focused on two tomato (Solanum lycopersicum) PSY isoforms, PSY1 and PSY2, and investigated their abilities to catalyze carotenogenesis via heterologous expression in transgenic Arabidopsis (Arabidopsis thaliana) and bacterial systems. We found that the fruit-specific PSY1 was less effective in promoting carotenoid biosynthesis than the green tissue-specific PSY2. Examination of the PSY proteins by site-directed mutagenesis analysis and three-dimensional structure modeling revealed two key amino acid residues responsible for this activity difference and identified a neighboring aromatic-aromatic combination in one of the PSY core structures as being crucial for high PSY activity. Remarkably, this neighboring aromatic-aromatic combination is evolutionarily conserved among land plant PSYs except PSY1 of tomato and potato (Solanum tuberosum). Strong transcription of tomato PSY1 likely evolved as compensation for its weak enzyme activity to allow for the massive carotenoid biosynthesis in ripe fruit. This study provides insights into the functional divergence of PSY isoforms and highlights the potential to rationally design PSY for the effective development of carotenoid-enriched crops. Carotenoids are a large class of lipophilic molecules that give flowers, fruits, and vegetables bright red, orange, and yellow color (Yuan et al., 2015b). In plants, carotenoids and their derivatives are critically important for plant survival and development (Nisar et al., 2015; Rodriguez-Concepcion et al., 2018; Wurtzel, 2019). Carotenoids are vital for photoprotection and contribute to light harvesting for photosynthesis (Niyogi and Truong, 2013; Hashimoto et al., 2016). They serve as precursors for biosynthesis of phytohormones abscisic acid and strigolactones (Nambara and Marion-Poll, 2005; Al-Babili and Bouwmeester, 2015) and are attractants to pollinators and seed-dispensing animals for plant reproduction. Carotenoid derivatives also act as signals for plant development and stress responses (Havaux, 2014; Hou et al., 2016) and provide aroma and flavors for fruits and vegetables. In addition, carotenoids provide precursors for vitamin A synthesis and are dietary antioxidants to lower the risks of some chronic diseases in humans (Fraser and Bramley, 2004; Rodriguez-Concepcion et al., 2018). Their essential roles in plants and health-promoting properties in humans have led to intense efforts to understand and manipulate carotenoids in plants (

Background/AimsThe diagnosis of spontaneous bacterial peritonitis (SBP) is based on a polymorphonuclear leukocytes (PMNs) exceeding 250/μL in ascitic fluid. The aim of the study was to evaluate serum procalcitonin and ascitic fluid calprotectin as accurate diagnostic markers for detecting SBP.MethodsSeventy-nine patients with cirrhotic ascites were included. They were divided into a SBP group, including 52 patients, and a non-SBP group of 27 patients. Serum procalcitonin, ascitic calprotectin, and serum and ascitic levels of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) were measured using an enzyme-linked immunosorbent assay.ResultsSerum procalcitonin and ascitic calprotectin were significantly higher in SBP patients than in non-SBP patients. Significant increases in both serum and ascitic levels of TNF-α and IL-6 were observed in SBP patients versus non-SBP patients. At a cutoff value of 0.94 ng/mL, serum procalcitonin had 94.3% sensitivity and 91.8% specificity for detecting SBP. In addition, at a cutoff value of 445 ng/mL, ascitic calprotectin had 95.4% sensitivity and 85.2% specificity for detecting SBP. Both were positively correlated with ascitic fluid proteins, PMN count, TNF-α, and IL-6.ConclusionsAccording to our findings, determination of serum procalcitonin levels and ascitic calprotectin appears to provide satisfactory diagnostic markers for the diagnosis of SBP.

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Introduction: The aim of this study was to evaluate the epidemiology and clinical significance of Cryptosporidium in patients with diarrhea and chronic liver diseases. Methodology: The study included 150 patients with chronic liver diseases and diarrhea, and 50 subjects with diarrhea as a control group. Stool samples were screened for the presence of Cryptosporidium by microscopic examination after modified Ziehl-Neelsen staining and detection of Cryptosporidium coproantigen by enzyme-linked immunosorbent assay (ELISA). Results: The prevalence of Cryptosporidium infection in patients with chronic liver diseases was 30% (45/150) versus 14% (7/50) in controls. Cryptosporidium infection increased with the progression of chronic liver diseases from Child-Pugh class A to Child-Pugh class C (p< 0.001) and from model for end-stage liver disease (MELD) score ≤ 9 to MELD score > 9 (p< 0.031). Nine patients in Child-Pugh class C with diarrhea associated with Cryptosporidium infection developed hepatic encephalopathy, and only diarrhea was identified as a precipitating factor for hepatic encephalopathy. Conclusions: Cryptosporidium is one of the important causes of diarrhea in patients with chronic liver diseases. The infection significantly increased with the progression of chronic liver diseases. In patients with advanced chronic liver diseases, Cryptosporidium infection may be a precipitating factor of hepatic encephalopathy.

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