A plastid-localized bona fide geranylgeranyl diphosphate synthase plays a necessary role in monoterpene indole alkaloid biosynthesis in Catharanthus roseus.

In plants, geranylgeranyl diphosphate (GGPP, C20 ) synthesized by GGPP synthase (GGPPS) serves as precursor for vital metabolic branches including specialized metabolites. Here, we report the characterization of a GGPPS (CrGGPPS2) from the Madagascar periwinkle (Catharanthus roseus) and demonstrate its role in monoterpene (C10 )-indole alkaloids (MIA) biosynthesis. The expression of CrGGPPS2 was not induced in response to methyl jasmonate (MeJA), and was similar to the gene encoding type-I protein geranylgeranyltransferase_ß subunit (CrPGGT-I_ß), which modulates MIA formation in C. roseus cell cultures. Recombinant CrGGPPS2 exhibited a bona fide GGPPS activity by catalyzing the formation of GGPP as the sole product. Co-localization of fluorescent protein fusions clearly showed CrGGPPS2 was targeted to plastids. Downregulation of CrGGPPS2 by virus-induced gene silencing (VIGS) significantly decreased the expression of transcription factors and pathway genes related to MIA biosynthesis, resulting in reduced MIA. Chemical complementation of CrGGPPS2-vigs leaves with geranylgeraniol (GGol, alcoholic form of GGPP) restored the negative effects of CrGGPPS2 silencing on MIA biosynthesis. In contrast to VIGS, transient and stable overexpression of CrGGPPS2 enhanced the MIA biosynthesis. Interestingly, VIGS and transgenic-overexpression of CrGGPPS2 had no effect on the main GGPP-derived metabolites, cholorophylls and carotenoids in C. roseus leaves. Moreover, silencing of CrPGGT-I_ß, similar to CrGGPPS2-vigs, negatively affected the genes related to MIA biosynthesis resulting in reduced MIA. Overall, this study demonstrated that plastidial CrGGPPS2 plays an indirect but necessary role in MIA biosynthesis. We propose that CrGGPPS2 might be involved in providing GGPP for modifying proteins of the signaling pathway involved in MIA biosynthesis.

Phytochemical profiling of Clerodendrum paniculatum leaf extracts: GC-MS, LC-MS analysis and comparative evaluation of antimicrobial, antioxidant & cytotoxic effects.

The present study evaluates the phytochemical content and biological activities of eight Clerodendrum paniculatum leaf extracts obtained using four solvents of varying polarity and two extraction methods. GC-HRMS analysis of the hexane extract predicted presence of phytol, 22-tritetracontanone, and 6,9,12-octadecatrienoic acid, phenyl methyl ester, (ZZZ)-as major compounds, and ethyl acetate extract was predicted to contain phytol. LC-HRMS analysis of methanolic extract exhibited the presence of 8',10'-dihydroxydihydroergotamine, Khayanthone, Galactonic acid, Calotropin, and 26,26,26,27,27,27-hexafluoro-1alpha,24-dihydroxy vitamin D3 as significant fractions. Ethyl acetate extract showed significant antimicrobial activity in-vitro. Methanolic extracts possess the highest radical scavenging activity (up to 87%) and antidiabetic activity (up to 49%) at 1 mg/mL concentration. Methanolic extracts from maceration and the Soxhlet method showed better cytotoxicity against breast and oral cancer cell lines, while the aqueous extract from maceration demonstrated better cytotoxicity against lung cancer cell lines. Methanolic extracts containing tannins, flavonoids, alkaloids, quinones, glycosides, terpenoids, diterpenoids, and phytosterols demonstrated significant bioactivity.

Digital contrast sensitivity chart with varying visual acuity: Development and validation.

BACKGROUND: Contrast sensitivity (CS) evaluation is very much necessary for the diagnosis and management of eye conditions. Several disadvantages seen in the traditionally used Pelli-Robson (PR) chart persuaded us to develop a novel digital device for the evaluation of CS at various levels of visual acuity (VA) for early detection of deteriorating vision. MATERIALS AND METHODS: The new chart was constructed on the Debian software. Letters were constructed at each level of VA from 6/60 to 6/6 with a contrast of 0-2.25 logCS. The newly constructed chart was validated against the PR chart. The data were analyzed on the SPSS software version 23. The Pearson's correlation test was used to find out the correlation between the digital CS chart (DCSC) and PR charts. RESULTS: On successful construction of a DCSC with varying VA, 56 participants were examined with a mean age of 20.43 ± 1.44 years. The mean CS with PR was 1.84 ± 0.13 logCS, whereas DCSC was 2.09 ± 0.14 logCS. The correlation between the two charts was moderate having r = 0.489 with P = 0 (confidence interval 95%). CONCLUSION: A newly developed CS chart is efficient in examining the CS in clinical practice and has good repeatability; it may help in the early detection and monitoring of ocular diseases.

The impact of COVID-19 on compliance to amblyopia treatment in a tertiary eye care center.

Purpose: To investigate the impact of the coronavirus disease 2019 (COVID-19) outbreak on compliance to amblyopia therapy from the perspective of parents of amblyopic children. Methods: The participants for the qualitative study were enrolled from the medical records of a tertiary eye care center during the COVID-19 pandemic. The trained researcher conducted telephonic interviews consisting of validated 15 open-ended questions for 15 min. The questions were related to patients' compliance toward amblyopia treatment and the date of follow-up with their practitioners. The data collected were entered on Excel sheets in the participant's own words and later converted to a transcript for analysis. Results: A total of 217 parents of children with amblyopia who were due for follow-up were contacted through telephone. The response rate for willingness to participate was only 36% (n = 78). Of these, 76% (n = 59) of parents reported that their child was compliant toward the treatment during the therapy period and 69% reported that their child was currently not on treatment for amblyopia. Conclusion: In the current study, we have observed that although reported compliance by parents during the therapy period was good, around 69% of patients had discontinued amblyopia therapy. The main reason for the discontinuation of therapy was the failure to visit the hospital during the scheduled follow-up with the eye care practitioner.

Isolation, identification and in vitro biological evaluation of phytochemicals from Memecylon randerianum: a medicinal plant endemic to Western Ghats of India.

The present investigation reports evaluation of phytochemical content, antimicrobial, antioxidant, antidiabetic and anticancer properties of the methanolic crude extracts prepared from Memecylon randerianum leaves. Qualitative evaluation showed the presence of carbohydrates, reducing sugars, alkaloids, phenols, flavonoids, cardiac glycosides, steroids, phytosterols, terpenoids, diterpenoids and coumarins. Quantitative estimation for phenols, flavonoids and alkaloids indicated total phenolic content 11.95 mg GAE/g, total flavonoid content 20.34 mg QE/g and total alkaloid content 316.68 mg AE/g dry weight of the crude extract respectively. The methanolic extract demonstrated effective antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans. The preparation also demonstrated good antioxidant and antidiabetic activities. Anticancer activity was evaluated against breast (MCF), oral (KB) and lung (A-549) cancer cell lines and the respective IC50 values were found to be 159.81 ± 7.54 µg/mL, 240.21 ± 2.57 µg/mL and 124.17 ± 2.10 µg/mL which are comparable to IC50 values of Paclitaxel.

Polyamine Induction in Postharvest Banana Fruits in Response to NO Donor SNP Occurs via l-Arginine Mediated Pathway and Not via Competitive Diversion of S-Adenosyl-l-Methionine.

Nitric oxide (NO) is known to antagonize ethylene by various mechanisms; one of such mechanisms is reducing ethylene levels by competitive action on S-adenosyl-L-methionine (SAM)-a common precursor for both ethylene and polyamines (PAs) biosynthesis. In order to investigate whether this mechanism of SAM pool diversion by NO occur towards PAs biosynthesis in banana, we studied the effect of NO on alterations in the levels of PAs, which in turn modulate ethylene levels during ripening. In response to NO donor sodium nitroprusside (SNP) treatment, all three major PAs viz. putrescine, spermidine and spermine were induced in control as well as ethylene pre-treated banana fruits. However, the gene expression studies in two popular banana varieties of diverse genomes, Nanjanagudu rasabale (NR; AAB genome) and Cavendish (CAV; AAA genome) revealed the downregulation of SAM decarboxylase, an intermediate gene involved in ethylene and PA pathway after the fifth day of NO donor SNP treatment, suggesting that ethylene and PA pathways do not compete for SAM. Interestingly, arginine decarboxylase belonging to arginine-mediated route of PA biosynthesis was upregulated several folds in response to the SNP treatment. These observations revealed that NO induces PAs via l-arginine-mediated route and not via diversion of SAM pool.