Changes in the Content of Organic Acids and Expression Analysis of Citric Acid Accumulation-Related Genes during Fruit Development of Yellow (Passiflora edulis f. flavicarpa) and Purple (Passiflora edulis f. edulis) Passion Fruits

Organic acids are key components that determine the taste and flavor of fruits and play a vital role in maintaining fruit quality and nutritive value. In this study, the fruits of two cultivars of passion fruit Yellow (Passiflora edulis f. flavicarpa) and purple (Passiflora edulis f. edulis) were harvested at five different developmental stages (i.e., fruitlet, green, veraison, near-mature and mature stage) from an orchard located in subtropical region of Fujian Province, China. The contents of six organic acids were quantified using ultra-performance liquid chromatography (UPLC), activities of citric acid related enzymes were determined, and expression levels of genes involved in citric acid metabolism were measured by quantitative real-time PCR (qRT-PCR). The results revealed that citric acid was the predominant organic acid in both cultivars during fruit development. The highest citric acid contents were observed in both cultivars at green stage, which were reduced with fruit maturity. Correlation analysis showed that citrate synthase (CS), cytosolic aconitase (Cyt-ACO) and cytosolic isocitrate dehydrogenase (Cyt-IDH) may be involved in regulating citric acid biosynthesis. Meanwhile, the PeCS2, PeACO4, PeACO5 and PeIDH1 genes may play an important role in regulating the accumulation of citric acid. This study provides new insights for future elucidation of key mechanisms regulating organic acid biosynthesis in passion fruit.     

Lymphocytes of Patients with Alzheimer’s Disease Display Different DNA Damage Repair Kinetics and Expression Profiles of DNA Repair and Stress Response Genes

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, characterized by loss of memory and cognitive capacity. Given the limitations to analyze brain cells, it is important to study whether peripheral lymphocytes can provide biological markers for AD, an interesting approach, once they represent the overall condition of the organism. To that extent, we sought to find whether lymphocytes of AD patients present DNA damage and repair kinetics different from those found in elderly matched controls (EC group) under in vitro treatment with hydrogen peroxide. We found that AD patient cells indeed showed an altered DNA repair kinetics (comet assay). Real-time quantitative analysis of genes associated with DNA stress response also showed that FANCG and CDKN1A are upregulated in AD, while MTH1 is downregulated, compared with the control group. In contrast, the expression of ATM, ATR and FEN1 genes does not seem to differ between these groups. Interestingly, TP53 protein expression was increased in AD patients. Therefore, we found that kinetics of the stress response in the DNA were significantly different in AD patients, supporting the hypothesis that repair pathways may be compromised in AD and that peripheral lymphocytes can reveal this condition.     

Genome-Wide Identification of Aquaporin Gene Family in Pitaya Reveals an HuNIP6;1 Involved in Flowering Process

Aquaporins (AQPs) are essential membrane proteins involved in seed maturation and germination, stomata movement, photosynthesis, and regulation of plant flowering processes. Pitaya flowers are open at night and wither at daybreak, which shows an obvious circadian rhythm. In this study, a comprehensive genome-wide analysis of AQPs in Hylocereus undantus was conducted to screen key genes associated with flowering processes. A total of 33 HuAQP genes were identified from the H. undantus genome. The 33 HuAQPs were grouped into four subfamilies: 10 PIPs, 13 TIPs, 8 NIPs, and 2 SIPs, which were distributed on 9 out of 11 pitaya chromosomes (Chr) (except for Chr7 and Chr10). Results from expression profiles showed that HuNIP6;1 may be involved in pitaya’s floral opening. HuNIP6;1 was localized exclusively in the cell membrane. Overexpression of HuNIP6;1 in Arabidopsis thaliana significantly promoted early flowering through regulating negative flowering regulators of MJM30, COL9, and PRR5, suggesting that HuNIP6;1 plays key roles in regulating flowering time. The present study provides the first genome-wide analysis of the AQP gene family in pitaya and valuable information for utilization of HuAQPs.