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[摘要]：Type III polyketide synthase family of enzymes play an important role in the biosynthesis of flavonoids and a variety of plant polyphenols by condensing multiple acetyl units derived from malonyl Co-A to thioester linked starter molecules covalently bound in the PKS active site. Turmeric (Curucma longa L) through diverse metabolic pathways produces a large number of metabolites, of which curcuminoids had gained much attention due to its immense pharmaceutical value. Recent identification of multiple curcuminoid synthases from turmeric lead us to look for additional Type III PKS from this plant. The current study describes the occurrence of a multigene family of Type III PKS enzymes in C. longa by RT-PCR based genomic screening. We have also isolated two new Type III PKS, CIPKS9 and CIPKS10 using homology based RT-PCR and data mining. The comparative sequence and phylogenetic analysis revealed that the two PKSs belong to different groups with only 56% sequence similarity at their amino acid level. CIPKS9 shows all possible sequence requirements for a typical chalcone synthase whereas CIPKS10 shows promising variation at amino acid level and high similarity to reported curcuminoid synthases. CIPKS9 and CIPKS10 exhibited distinct tissue specific expression pattern in C. longa with the CIPKS9 transcript abundant in shoot and rhizome than leaves whereas CIPKS10 transcript was found to be high in leaf and very low in rhizome and root. Therefore it was concluded that CIPKS9 and CIPKS10 may have divergent function in planta, with possible role in typical chalcone forming reaction and curcuminoid scaffold biosynthetic pathway respectively. (C) 2011 Elsevier B.V. All rights reserved. |
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