Suberin

Suberins form gas- and water-impermeable layers between cells Suberin is the polymeric compound formed from phenyl propanoids, long chain fatty acids and fatty alcohols (C18–C30), as well as the hydroxyl fatty acids and dicarboxylic acids (C14–C20). In suberin, the phenyl propanoids are to some extent related with each other as in lignin. However, most of the 9′-OH groups are not involved in the specific linkages and instead form esters with fatty acids.
Often two phenyl propanoids are connected by a dicarboxylic acid via ester linkages, and fatty acids and hydroxyl fatty acids also can form esters with each other (Fraser et al., 1978). Although the mechanism of suberin synthesis is to a large extent still not known or yet to be explored, it appears that the peroxidases are also involved in this process (Foster et al., 1983).
Suberin is a cell wall comprises that forms gas- and watertight layers. It is portion of the Casparian strip of the root endodermis

1. BY Dr. S.SREEREMYA FACULTY OF BIOLOGY Suberin

2. INTRODUCTION Suberins form gas- and water-impermeable layers between cells Suberin is the polymeric compound formed from phenyl propanoids , long chain fatty acids and fatty alcohols (C18–C30), as well as the hydroxyl fatty acids and dicarboxylic acids (C14–C20). In suberin , the phenyl propanoids are to some extent related with each other as in lignin. However, most of the 9′-OH groups are not involved in the specific linkages and instead form esters with fatty acids.

3. Often two phenyl propanoids are connected by a dicarboxylic acid via ester linkages, and fatty acids and hydroxyl fatty acids also can form esters with each other (Fraser et al., 1978). Although the mechanism of suberin synthesis is to a large extent still not known or yet to be explored, it appears that the peroxidases are also involved in this process (Foster et al., 1983). Suberin is a cell wall comprises that forms gas- and watertight layers. It is portion of the Casparian strip of the root endodermis

4. Suberin is present in many of the C4 plants as an impermeable layer between the bundle sheath and mesophyll cells. Cork tissue, comprising of dead cells surrounded by alternating layers of suberin and wax, has particularly high suberin content (Fraser et al., 1979). Cork cells are found in the secondary protective layer called the periderm and in the bark of trees. Cork layers comprising suberin protect plants against loss of water, infection by microorganisms, and heat exposure ( Franich et al., 1982). Due to this, some plants even survive short fires and are mstlyable to continue growing afterwards (Freudenberg, 1978).

5. Biochemistry and functions of suberin in rhizospheres Suberin is the complex biopolymer found on the inner face of primary cell walls in aerial and root parts of the plant(Fig:1). Polyaliphatics and polyaromatics are the major molecular components ( Fussel et al., 1980). The aliphatic domain is an insoluble polyester hugely comprised of fatty acids and glycerol, such as ω- hydroxy fatty acids, α,ω- dicarboxylic acids, mid-chain oxygenated fatty acids, unsubstituted fatty acids, and primary fatty alcohols( Godkin et al.,1978).

6. The phenylpropanoid -derived aromatic domain mostly encompasses of ferulate , which is a p- hydroxycinnamic acid (Geiger et al., 1986). Suberin is also copious in monomers ranging in size from C20 to C24 ( Glazener , 1982). The relative abundance of suberin monomer constituents differs considerably between species ( Godkin et al., 1977). Another much major component of the suberin aliphatic domain is glycerol, which in partial depolymerization experiments is found esterified to ω- hydroxy fatty acids and α,ω- dicarboxylic acids(Gibson,1981). SUBERIN BIOSYNTHESIS

7. Deposition of the suberin requires biosynthesis of aliphatic, phenolic and glycerol monomers, and then the transportation to the cell wall to form an insoluble macromolecular assembly ( Godkin et al., 1983). Although the monomeric composition of the suberin bio-polymer is known for a broad variety of plants, numerous processes underlying suberin biosynthesis, such as the sequence of biosynthetic reactions, transport mechanism of the monomers, and controlled polymerization, remain elusive(Goldberg et al.,1985).The development of quantitative analytical equipments to measure suberin composition following depolymerisation and the characterization of Arabidopsis mutants with altered suberin composition have been pivotal to identifying most of the genes encoding enzymes involved in suberin biosynthesis (Gômez-Vazquez,1984).