Isolation cloning and characterization of lignin biosynthesis pathway genes) 4-coumarate co a ligase (4cl) from leucaena leucocephala

Abstract

Leucaena sp. is a fast growing multipurpose tree adapted to a variety of soils and climatic conditions. Leucaena is recognized as most useful trees in the tropics. Paper industry in India mainly uses bamboos, Eucalyptus sp., Casuarina sp. and Leucaena sp. as a source for paper pulp. This hard wood Leucaena sp. is exclusively used in India and about 25% of raw material for pulp and paper industry comes from this plant. To meet the increasing demand of high quality wood for paper industry, it is essential to provide designer plant species. The present study was aimed at understanding lignin biosynthesis pathway in Leucaena leucocephala. No study has been done so far in this regard anywhere on Leucaena sp. 4CL (4-Coumarate CoA Ligase, EC (6.2.1.1.2)) is one of the important key enzymes of general phenyl propanoid metabolism, which provides the precursor molecules for a large variety of important plant secondary products such as lignin, flavonoid etc. It catalyzes the activation of 4-coumarate and various other cinnamic acid derivatives to the corresponding thiol esters in two-step reaction via an adenylate intermediate. Thie reaction represents the last step in a short series of biochemical conversions, known as phenyl propanoid metabolism leading from phenylalanine to the activated cinnamic acid derivatives. These derivatives are precursors for the biosynthesis of a large variety of plant secondary metabolites. This gene was chosen as the target gene for the study if we could down regulate this 4CL enzyme then there would be scarcity of precursor molecules for lignin biosynthesis i.e. total lignin content of plant will get altered. Thus it may be helpful for development of transgenic L. leucocephala plants with desired characters suitable for Indian pulp and paper industry. The main features of the present thesis are: and#56256; and#56451; Cloning and characterization of 4-coumarate CoA ligase (4CL) gene from Leucaena leucocephala.