Expression profile of phenylpropanoid pathway genes in Decalepis hamiltonii tuberous roots during flavour development.

To explore the transcriptional control of phenylpropanoid pathway (PPP) involved in vanillin flavour metabolites production in tuberous roots of Decalepis hamiltonii, four PPP key genes expressed during the tuber development were identified and their mRNA expression profiles were evaluated using quantitative real-time PCR. Flavour metabolite quantification by HPLC analysis confirmed 10, 170 and 500 µg/g 2-hydroxy-4-methoxy benzaldehyde and 4, 20 and 40 µg/g vanillin in first- (3-month-old plant), second- (18-month-old plant) and third-stage tubers (60-month-old matured plant), respectively. The expression of all four genes phenylalanine ammonia lyase (DhPAL), cinnamate-4-hydroxylase (DhC4H), caffeic acid-O-methyltransferase (DhCOMT) and vanillin synthase (DhVAN) increased with flavour development from first stage to second stage. A decrease in expression from 1.9-folds to 0.1-folds and 19.2-folds to 5.2-folds for DhCOMT and DhVAN was recorded for second stage to third stage, respectively. However, a gradual increase in expression of DhPAL (up to 26.4-folds) and a constant expression pattern for DhC4H (up to 7.1-folds) was evident from second stage to third stage of flavour development. The decrease in the expression levels of DhCOMT and DhVAN in third stage shows that the second-stage tubers are more transcriptionally active towards flavour biosynthesis.

Evaluation of folate-binding proteins and stability of folates in plant foliages.

The present study reports the presence of folate binding proteins (FBPs) in the plants, coriander and Arabidopsis, and their contributions toward folate enhancement. After observing that salicylic acid (SA) enhanced the accumulation of folates in coriander, a study was conducted in Arabidopsis, where twofold increase in folates occurred in foliage upon SA treatment. For obtaining insights into genes involved in SA-induced folate accumulation, microarray data of responsive genes in Arabidopsis were screened. Based on the expression profiles, 19 genes were further analysed by qPCR. The results revealed that folate biosynthetic genes were largely down-regulated, whereas a gene of a putative folate-binding protein (FPB) was up-regulated, which correlated with a significant increase of FPBs in foliage. This new information on a plant FBP appears useful for metabolic engineering of a wide range of crops to enhance the content and stability of the folates during post-harvest storage.