Differential Expression of Genes Related to Fruit Development and Capsaicinoids Synthesis in Habanero Pepper Plants Grown in Contrasting Soil Types

Habanero pepper(Capsicum chinense Jacq.)is a crop of economic relevance in the Peninsula of Yucatan.Its fruits have a high level of capsaicinoids compared to peppers grown in other regions of the world,which gives them industrial importance.Soil is an important factor that affects pepper development,nutritional quality,and capsaicinoid content.However,the effect of soil type on fruit development and capsaicinoid metabolism has been little understood.This work aimed to compare the effect of soils with contrasting characteristics,black soil(BS)and red soil(RS),on the expression of genes related to the development of fruits,and capsaicinoid synthesis using a transcriptomic analysis of the habanero pepper fruits.Plants growing in RS had bigger fruits and higher expression of genes related to floral development,fruit abscission,and softening which suggests that RS stimulates fruit development from early stages until maturation stages.Fruits from plants growing in BS had enrichment in metabolic pathways related to growth,sugars,and photosynthesis.Besides,these fruits had higher capsaicinoid accumulation at 25 days post-anthesis,and higher expression of genes related to the branched-chain amino acids metabolism(ketol-acid reductisomerase KARI),pentose phosphate pathway and production of NADPH(glucose-6-phosphate-1-dehydrogenase G6PDH),and proteasome and vesicular traffic in cells(26S proteasome regulatory subunit T4 RPT4),which suggest that BS is better in the early stimulation of pathways related to the nutritional quality and capsaicinoid metabolism in the fruits.

Gender May Affect the Dose-Dependent Action of Capsaicinoids on Plasma and Hepatic Cholesterol Levels of Rats

Sex differences on the effect of dose-dependent capsaicinoids on lipid metabolism were studied in rats. 24 rats of each sex were administered orally 0 mg/kg, 2.5 mg/kg, 5 mg/kg or 7.5 mg/kg capsaicinoids daily for 28 days. In male rats, body weight gained, and the levels of total lipids, total cholesterol and triglycerides in the liver were significantly decreased as the dose of capsaicinoids increased. On the other hand, plasma total cholesterol (TC), triglycerides (TG), HDL- and LDL-cholesterol concentration and liver weight were not affected by capsaicinoids. While in female rats, plasma TC, TG, HDL-C and LDL-C concentration, liver total lipids, TC and TG concentration were significantly decreased as the dose of capsaicinoids increased. The mRNA level of hepatic TRPV1, ileac ASBT and IBABP were increased as the dose of capsaicinoids increased in all rats groups. The mRNA level of hepatic HMG-CoA reductase, CYP7A1 and FXR were significantly decreased in female rats groups. These results show that the hypocholesterolemic effect of capsaicinoids in dose-dependent manner in rats was mediated by inhibited synthesis of endogenous cholesterol, female rats were more sensitive than male rats on hypolipidemic effect of capsaicinoids.

Chromatographic Separation and Characterization of Capsaicinoids and Their Analogues

An attempt was made to establish a chromatographic separation and analysis method for capsaicinoids and their analogues. A series of factors,such as choice of column and eluents, eluent composition,flow rate of eluent and operational temperature were correlated, countereacted and optimized to attain appropriate separation efficiency and finalize the experimentally oprational procedures as a whole, permiting a mixture comprising 8 capsaicinoids including analogues to be separated and Characterized with an allowed deviations and within a period of 36 minutes via 1 test as well.

A <i>Comt</i>1 Loss of Function Mutation Is Insufficient for Loss of Pungency in <i>Capsicum</i>

The participation of O-methyltransferase (COMT) in phenylpropanoid-mediated capsaicinoid biosynthesis has long been proposed. Ferulic acid, a phenylpropanoid intermediate, is a precursor of capsaicinoid biosynthesis and is produced from caffeic acid by the action of COMT. As previously reported that silencing Comt expression caused a drastic decrease in capsaicinoid accumulation, it was presumed that a Comt loss-of-function mutation would cause loss of pungency in Capsicum. This hypothesis was tested by cloning Comt1 and Comt2 from the placenta tissue of the pungent cultivar Habanero. The phylogenetic analysis and comparison of critical amino-acid residues for enzyme function showed that the two COMTs had high similarity with the COMTs of other plant species. Moreover, as the two Comts were both expressed in placenta tissue and expressed prior to the accumulation of capsaicinoids, the two genes could be candidates for capsaicinoid biosynthesis. Second, Comt1 loss-of-function mutants were screened from the germplasm. A truncated Comt1 transcript was expressed in non-pungent pepper No.3341 caused by deletion of the genomic region. The predicted No.3341 COMT1 lacked His-265, which was absolutely necessary for enzymatic activity. Contrary to our expectations, the Comt1 mutation was not related to non-pungency of No.3341, as the deletion of Comt1 did not co-segregate with non-pungency in the F2 population obtained from crossing No.3341 with Habanero. This result was confirmed by screening several pungent accessions harboring the same Comt1 deletion mutation. Although the participation of COMT in phenylpropanoid-mediated capsaicinoid biosynthesis has long been proposed, our present study shows that Comt1 can not be a target for controlling fruit pungency.

A Study of Pungency of Capsaicinoid as Affected by Their Molecular Structure Alteration

An attempt was made in an effort to synthesize a series of capsaicinoids, most of which are synthesized in our laboratory and characterized to be completely new members of capsaicinoids. The Structure-pungency dependence are presented and discussed.

The bio-interactions between plants,insecticides and fertilizers:an innovative approach for the research of xenobiotic substances

In this experiment carried out on Caribbean chili pepper plants(Capsicum chinensis),the bio-insecticide azadirachtin in combination with an NPK fertilizer proved to have a greater lethal impact on the larvae of Aedes albopictus than each substance on its own.This synergistic effect is noticeably important when both inputs are sprayed directly on the leaves of the plant(foliar application).While the plants treated with azadirachtin or NPK alone cause a 33.6%and 36.4%mortal-ity respectively of the Ae.albopictus larvae,the combination of the two inputs induces a 74.4%mortality on the mosquito larvae.To account for this synergistic effect phenomenon inside the plant,the azadirachtin+NPK combination most likely interacts with the capsaicinoid compounds naturally produced by the plant.Not only does this study carried out on azadirachtin reveal major results but the methodology itself offers a most interesting approach on how to boost the agricultural inputs within the plants.As a matter of fact,this research axis demands developing since the control of pests harmful to men has been dramatically lacking insecticide molecules acting on new targets over the past three decades.

Effect of gamma radiation and storage at 4°C on the inactivation of Listeria monocytogenes,Escherichia coli and Salmonella enterica Typhimurium in Legon-18 pepper(Capsicum annuum)powder

Objectives:Spices are low moisture foods which have been known to be contaminated with various pathogens and sun-dried Legon-18 pepper powder is not left out.Due to its contamination with various pathogens,a study was conducted to determine the effects of gamma irradiation on the decontamination of Legon-18 pepper powder and on some quality parameters.Methods:Samples were obtained from a local farmer from the Eastern Region of Ghana.Sterility tests were carried out.The samples were inoculated with known cfu/ml of Escherichia coli,Listeria monocytogenes and Salmonella enterica Typhimurium.Samples were irradiated at 1,2,4,and 5 kilogray(kGy).Zero kilogray served as control(unirradiated).All samples were stored at 4oC for 60 days.Enumeration of the various pathogens was done in appropriate media.Some quality parameters were determined after irradiating unsterile samples at 5 kGy and 0 kGy served as control.Capsaicinoids and carotenoids were quantified using a high performance liquid chromatography.The samples were stored at 4oC for 8 weeks.Results:A dose-dependent effect on the inactivation of the pathogens was observed(P<0.05).Storage time affected the inactivation of the pathogens as well(P<0.05).Complete inactivation of the pathogens was observed at 5 kGy at day 0.Capsaicin,dihydrocapsaicin and total capsaicinoid content of the samples irradiated at 5 kGy increased at 23.64%,14.7%and 20.95%respectively as compared with the contents of the unirradiated samples.A gamma irradiation dose of 5 kGy caused losses of 8.11%,8.67%and 26.54%in capsanthin,beta carotene and beta cryptoxanthin respectively.Quality parameters measured reduced with storage(P<0.05).Conclusions:Gamma irradiation inactivated pathogens at 5 kGy.Lower doses used during the study could inactivate the pathogens but with time.All quality parameters and carotenoids quantified were affected by gamma irradiation and storage period(P<0.05).