RESUMO
High hydrostatic pressure (HHP) processing is a non-thermal technology reported to increase desirable metabolites in plant foods. This work evaluated changes in carotenoid accumulation in fresh-cut papaya fruit as affected by HHP treatment (50-400â¯MPa for 3-60â¯min) and during subsequent storage at 4⯰C; simultaneously, transcriptional activities of carotenoid biosynthetic genes and oxidative stress markers were evaluated. LC-MS analyses revealed that HHP treatment increased carotenoid precursors and carotenes contents following processing and storage: lycopene levels increased up to 11-fold compared to the non-treated samples, and H2O2 and lipid peroxidation were concomitantly increased. qRT-PCR of intact RNA showed that the amount of phytoene desaturase transcripts increased after HHP treatment, and that they were correlated with carotene accumulation. This is the first study to show that HHP treatment triggers de novo carotenoid biosynthesis, which is regulated at the transcriptional level, possibly by inducing oxidative stress signaling in fruit tissue.
Assuntos
Carica/metabolismo , Carotenoides/biossíntese , Frutas/metabolismo , Carica/genética , Cromatografia Líquida , Temperatura Baixa , Manipulação de Alimentos , Frutas/genética , Regulação da Expressão Gênica de Plantas , Peróxido de Hidrogênio/metabolismo , Pressão Hidrostática , Peroxidação de Lipídeos/efeitos dos fármacos , Licopeno/análise , Análise Multivariada , Estresse Oxidativo/efeitos dos fármacos , Oxirredutases/genética , Oxirredutases/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ativação Transcricional/genéticaRESUMO
Folate (vitamin B9) deficiency causes several health problems globally. However, folate biofortification of major staple crops is one alternative that can be used to improve vitamin intakes in populations at risk. We increased the folate levels in common bean by engineering the pteridine branch required for their biosynthesis. GTP cyclohydrolase I from Arabidopsis (AtGchI) was stably introduced into three common bean Pinto cultivars by particle bombardment. Seed-specific overexpression of AtGCHI caused significant increases of up to 150-fold in biosynthetic pteridines in the transformed lines. The pteridine boost enhanced folate levels in raw desiccated seeds by up to threefold (325 µg in a 100 g portion), which would represent 81% of the adult recommended daily allowance. Unexpectedly, the engineering also triggered a general increase in PABA levels, the other folate precursor. This was not observed in previous engineering studies and was probably caused by a feedforward mechanism that remains to be elucidated. Results from this work also show that common bean grains accumulate considerable amounts of oxidized pteridines that might represent products of folate degradation in desiccating seeds. Our study uncovers a probable different regulation of folate homoeostasis in these legume grains than that observed in other engineering works. Legumes are good sources of folates, and this work shows that they can be engineered to accumulate even greater amounts of folate that, when consumed, can improve folate status. Biofortification of common bean with folates and other micronutrients represents a promising strategy to improve the nutritional status of populations around the world.
Assuntos
Ácido Fólico/genética , Ácido Fólico/metabolismo , Engenharia Metabólica , Phaseolus/genética , Phaseolus/metabolismo , Plantas Geneticamente Modificadas , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Biofortificação , GTP Cicloidrolase/genética , GTP Cicloidrolase/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismoRESUMO
Folates are essential micronutrients for humans, and their deficiency causes several detrimental effects on human health. Papaya fruit is an important natural source of some micronutrients. This paper presents a first complete characterization of folate derivatives accumulated in cv. Maradol papaya during fruit development and ripening processes. During postharvest ripening, the fruit accumulated up to 24.5% of the daily folate recommended dietary allowance (RDA) for an adult in a 1 cup (145 g) portion. Tetrahydrofolate (THF) and 5-methyl-THF were the predominant folate classes observed. Surprisingly, an unusually long polyglutamylation profile of tentatively up to 17 glutamates linked to 5-methyl-THF was detected; to the authors' knowledge, this very long polyglutamyl tail has not been reported for any organism, and it is probably characteristic of this plant species. This polyglutamylation degree changed throughout fruit development and ripening, showing the largest differences at the onset of ripening. This work raises questions about the functional role of folate derivatives in fruit development.