Proteomic approach to identify the differentially abundant proteins during flavour development in tuberous roots of Decalepis hamiltonii Wight & Arn.

2-Hydroxy-4-Methoxy Benzaldehyde (2H4MB) is a structural isomer of vanillin produced in the tuberous roots of D. hamiltonii. Both vanillin and 2H4MB share the common phenylpropanoid pathway for their synthesis. Unlike vanillin, in which the biosynthetic pathway was well elucidated in V. planifolia, the 2H4MB biosynthetic pathway is not known in any of its plant sources. To find the key enzymes/proteins that promote 2H4MB biosynthesis, a comparative proteomic approach was adapted. In this case, two developmental stages of tuberous roots of D. hamiltonii were selected, where the flavour content was highly variable. The flavour content in the two stages was estimated using quantitative HPLC. The flavour content in the first and second stages of tuber development was 160 and 510 mu gg(-1), respectively. Two-dimensional electrophoresis (2-DE) was performed for these two stages of tubers; this was followed by PDquest analysis. A total of 180 protein spots were differentially abundant of which 57 spots were selected and subjected to MALDI-TOF-TOF analysis. The largest percentage of identified proteins was involved in stress and defence (27.9%), followed by proteins related to bioenergy and metabolism (23.2%), Cellular homeostasis proteins (18.6%), signaling proteins (11.6%), Plant growth and development proteins (9.3%). Holistically, we found the upregulation of methyltransferase, cell division responsive proteins, plant growth and development proteins which directly relate to flavour development and maturation. Similarly, stress-responsive and signaling proteins, vacuole proteins and ATPases were down-regulated with an increase in flavour content. In this study, we could not identify the specific 2H4MB metabolic pathway proteins, however, we could be able to study the changes in physiological and primary metabolic proteins with 2H4MB accumulation.

Automated summary

The study investigated the biosynthetic pathway of 2-Hydroxy-4-Methoxy Benzaldehyde (2H4MB) in the tuberous roots of D. hamiltonii using a comparative proteomic approach. It was found that proteins related to flavor development and maturation were upregulated during 2H4MB accumulation, while stress-responsive and signaling proteins were downregulated.