Lignin Deposition in Cotton Cells ? Where is the lignin?

Abstract

and poplar have been investigated, detailed examination of lignin deposition in agriculturally important crops such as cotton has been very limited. Lignin is a complex polymeric structure of phenolic compounds containing monolignols (coniferyl alcohol (guaiacyl, G-lignin monomer), sinapyl alcohol (sinapyl, S-lignin monomer), p-coumaryl alcohol (hydroxyphenyl, H-lignin monomer) and 5-OH coniferyl alcohol (5-hydroxyguaiacyl, 5-OH G-lignin monomer)) [1]. The key genes involved in lignin biosynthesis have been identified and functionally characterized in model plants allowing the realisation of lignin manipulation for potential useful application in plants (reviewed by Bedon and Legay) [2]. The lignin monomers are generally associated with the plant secondary cell wall (SCW) typified by specialised cells such as xylem vessels, xylem fibres in angiosperms, and tracheids in gymnosperms. The SCWs in these cells function to allow water transport via xylem vessels and tracheids, to provide mechanical support via tracheids, xylem fibres and phloem fibres, and to protect against biotic attack and abiotic stresses. The physical properties of lignin that contribute to its roles in different cell types is highly dependent on its quantity and quality, the latter determined by the ratio of the monolignols and how they are covalently linked. Cotton