[Molecular studies in the cork-oak tree, Quercus suber L.. Detection of proteins associated with suberin [Portugal]]
2000
Nobrega, F. | Vidal, R. | Sousa, C.B. de | Sousa, R.B. de | Sardinha, R.
Suberin is the main constituent of the cork in which it normally comprises 30 to 58% of its dry weight. The chemical composition of the cork oak suberin, Quercus suber L., still remains relatively unknown. However, it is known that it contains 2 domains (an aliphatic covalently linked through esters bonds to another phenolic one) and that the glycerol is a part ot its esterified regions. The cork cellular walls also contain polysaccharides whose integrity reflect the physico-chemical caracteristics of the high and low quality cork (CBQ and CMQ, respectively), resulting from a related defect known ai industrial applications as "yellow spot". With a view to ascertaining whether other molecular markers, notably proteic, can or cannot be established to differentiate between the 2 types of cork, samples of CBQ and CMQ were sequentially extracted using alkaline methanolysis (0.058 NaOH M in methanol) and chloroform and the respective residues were submitted to 4 different procedures (extraction with NaOH 1M, extraction with organic solvents, fractionation with ammonium sulphate and chromatographic adsorption of ionic exchange). The results show for the first time (to the best of our knowledge) the protein occurrence of different molecular dimensions (notably, one of 60-70 KDa) directly or indirectly associate with the suberin extracted from the cork. These proteins allowing a clear differentiation to be established with the 2 types of cork oak in question may be used as molecular markers. It was also verified that the suberin of the CBQ and the CMQ are esterified with glycerol, with a CBQ suberin triglycerides content of about 1.22 times higher than the CMQ suberin
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