RESUMO
Phenylalanine ammonia lyase (PAL) and p-coumarate 3-hydroxylase (C3H) are key enzymes in the phenylpropanoid pathway. The relative expression of PAL and C3H was evaluated in mango fruit cultivar 'Ataulfo' in four ripening stages (RS1, RS2, RS3, and RS4) by quantitative polymerase chain reaction. In addition, enzyme activity of PAL and C3H was determined in mango fruits during ripening. The PAL levels were downregulated at the RS2 and RS3 stages, while C3H levels were upregulated in fruits only at RS3. The enzyme activity of PAL followed a pattern that was different from that of the PAL expression, thus suggesting regulation at several levels. For C3H, a regulation at the transcriptional level is suggested because a similar pattern was revealed by its activity and transcript level. In this study, the complexity of secondary metabolite biosynthesis regulation is emphasized because PAL and C3H enzymes are involved in the biosynthesis of several secondary metabolites that are active during all mango ripening stages.
Assuntos
Frutas/crescimento & desenvolvimento , Mangifera/genética , Oxigenases de Função Mista/biossíntese , Fenilalanina Amônia-Liase/biossíntese , Clonagem Molecular , Frutas/genética , Regulação da Expressão Gênica de Plantas , Mangifera/crescimento & desenvolvimento , Oxigenases de Função Mista/genética , Fenilalanina Amônia-Liase/genética , Reação em Cadeia da PolimeraseRESUMO
Ethylene induces characteristic ripening reactions in climacteric fruits through its binding to histidine-kinase (HK) receptors, activating the expression of ripening genes. Ethylene receptors have been found in Arabidopsis thaliana (Brassicaceae) and some fruits; number and expression patterns differ among species. In mango, only ethylene receptor ETR1 was known. We cloned ERS1 cDNA from mango, and evaluated the expression of Mi-ERS1 and Mi-ETR1 by qPCR in developmental and ripening stages of this fruit. The Mi-ERS1 coding sequence is 1890 bp long and encodes 629 amino acids, similar to ERS1 from other fruits. Also, the amino acid sequence of ERS1 C-terminal HK domain shows the cognate fold after molecular modeling. Mi-ERS1 expression levels increased as mangoes ripened, showing the highest levels at the climacteric stage, while Mi-ETR1 levels did not change during development and ripening. We conclude that the patterns of expression of Mi-ERS1 and Mi-ETR1 differ in mango fruit.
