Modules of co-regulated metabolites in turmeric (Curcuma longa) rhizome suggest the existence of biosynthetic modules in plant specialized metabolism

Abstract

Turmeric is an excellent example of a plant that produces large numbers of metabolites from diverse metabolic pathways or networks. It is hypothesized that these metabolic pathways or networks contain biosynthetic modules, which lead to the formation of metabolite modules—groups of metabolites whose production is co-regulated and biosynthetically linked. To test whether such co-regulated metabolite modules do exist in this plant, metabolic profiling analysis was performed on turmeric rhizome samples that were collected from 16 different growth and development treatments, which had significant impacts on the levels of 249 volatile and non-volatile metabolites that were detected. Importantly, one of the many co-regulated metabolite modules that were indeed readily detected in this analysis contained the three major curcuminoids, whereas many other structurally related diarylheptanoids belonged to separate metabolite modules, as did groups of terpenoids. The existence of these co-regulated metabolite modules supported the hypothesis that the 3-methoxyl groups on the aromatic rings of the curcuminoids are formed before the formation of the heptanoid backbone during the biosynthesis of curcumin and also suggested the involvement of multiple polyketide synthases with different substrate selectivities in the formation of the array of diarylheptanoids detected in turmeric. Similar conclusions about terpenoid biosynthesis could also be made. Thus, discovery and analysis of metabolite modules can be a powerful predictive tool in efforts to understand metabolism in plants.

Comparative Functional Genomic Analysis ofSolanumGlandular Trichome Types

“…3; Supplemental Figs. S1 and S2; Supplemental Table S2; Xie et al, 2009). The normalized data used to produce Figure 3 revealed that the known metabolites observed in Solanum trichomes are differentially distributed between trichome types and species and that this variation is generally more evident between species than within.…”

Heterologous Production of Curcuminoids

“…The biosynthetic pathway of these diarylheptanoids has not yet been elucidated and several routes have been hypothesized. Xie et al (104), after using metabolic profiling analysis, proposed that the biosynthetic pathway belongs to a different metabolite module (Fig. 2) and that they are not intermediates in curcuminoid biosynthesis that belong to another biosynthetic module (Fig.…”

“…1), which cannot use caffeoyl-CoA as a substrate and produce the major curcuminoids. Furthermore, Xie et al (104) reported that some PKS, instead of using caffeoyl-CoA, use 5-hydroxy-feruloyl-CoA or feruloyl-CoA and coumaroylCoA to produce 5=-hydroxy-curcumin and 5=-hydroxy-demethoxycurcumin, respectively. Dihydrocurcuminoids, which are dihydro derivatives of curcuminoids (103), have also been identified in C. longa, for example, di- hydrodemethoxycurcumin, dihydrobisdemethoxycurcumin, and dihydrocurcumin.…”

Digitizing the metabolome

“…An exciting and promising approach to understand these mechanisms is described in the paper by Xie et al (2009). The authors have coupled state of the art metabolomic analyses with novel bioinformatic techniques to identify apparent 'metabolic modules' in turmeric (Curcuma longa) rhizomes.…”

“…Sixteen different growth and development treatments were performed and metabolically profiled, followed by hierarchical cluster analysis in order to detect co-regulated volatile and non-volatile metabolites. Biosynthetic relationship predictions were then made using the metabolite modules that resulted from the processing of the metabolomic information collected (Xie et al, 2009). The dissection of the metabolic information into metabolic modules led to the conclusion that more than one polyketide synthase is involved in diarylheptanoid biosynthesis in turmeric rhizomes, but the potential for using a similar approach in deciphering complex and apparently unrelated metabolic pathways is also very promising.…”