AtROS1 overexpression provides evidence for epigenetic regulation of genes encoding enzymes of flavonoid biosynthesis and antioxidant pathways during salt stress in transgenic tobacco.

In plants, epigenetic changes have been identified as regulators of developmental events during normal growth as well as environmental stress exposures. Flavonoid biosynthetic and antioxidant pathways play a significant role in plant defence during their exposure to environmental cues. The aim of this study was to unravel whether genes encoding enzymes of flavonoid biosynthetic and antioxidant pathways are under epigenetic regulation, particularly DNA methylation, during salt stress. For this, a repressor of silencing from Arabidopsis, AtROS1, was overexpressed in transgenic tobacco. Generated transgenics were evaluated to examine the influence of AtROS1 on methylation status of promoters as well as on coding regions of genes encoding enzymes of flavonoids biosynthesis and antioxidant pathways. Overexpression of AtROS1 increases the demethylation levels of both promoters as well as coding regions of genes encoding chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase, flavonol synthase, dihydroflavonol 4-reductase, and anthocyanidin synthase of the flavonoid biosynthetic pathway, and glutathione S-transferase, ascorbate peroxidase, glutathione peroxidase, and glutathione reductase of the antioxidant pathway during control conditions. The level of demethylation was further increased at promoters as well as coding regions of these genes during salt-stress conditions. Transgenic tobacco overexpressing AtROS1 showed tolerance to salt stress that could have been due to the higher expression levels of the genes encoding enzymes of the flavonoid biosynthetic and antioxidant pathways. This is the first comprehensive study documenting the epigenetic regulation of flavonoid biosynthetic and antioxidant pathways during salt-stress exposure of plants.

Association of Acanthosis Nigricans and Acrochordon with Insulin Resistance: A Cross-Sectional Hospital-Based Study from North India.

BACKGROUND: Insulin resistance (IR) is a pre-diabetic condition and has been reported in patients with acanthosis nigricans (AN) and acrochordon. AN and acrochordon are claimed to be cutaneous markers of IR. AIM: The purpose of this paper was to study the association of AN and acrochordon with IR. METHODS: It was a cross-sectional hospital-based study. Both groups were assessed for IR by using homeostatic model assessment of insulin resistance (HOMA-IR) formula. RESULTS: A total of 70 cases and an equal number of controls were studied. IR was observed more in cases (41.4%) compared to controls (17.1%) (P < 0.01). Mean HOMA-IR value was also significantly higher in cases (4.32 ± 4.44) compared to controls (2.27 ± 0.90) (P < 0.05). LIMITATIONS: Low number of cases and controls were taken in the study. Association with hyperlipidemia and metabolic syndrome was not elicited. CONCLUSIONS: AN and acrochordons were found to be associated with IR.