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Proteolysis in the quiescent seed
Author(s) -
Duarte Isabel,
Ricardo Cándido P. P.,
DuqueMagalhäes Maria C.
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1996.tb00467.x
Subject(s) - proteolysis , proteases , cotyledon , imbibition , autolysis (biology) , protease , biology , storage protein , biochemistry , proteolytic enzymes , botany , enzyme , germination , gene
The importance of the proteolytic system of the quiescent seed in regard to mobilization of storage protein was assessed by identification of proteases already present at this stage. Extracts of quiescent cotyledons of white lupin ( Lupinus albus ) submitted to 45 h autolysis in vitro displayed a higher degree of protein degradation than that observed in vivo after two days of seed imbibition. Differences in the susceptibility to proteolysis were verified by densitometric analysis of the polypeptides after electrophoretic separation. The pH dependence of the proteolytic activities and the responses to specific protease inhibitors showed that the proteolytic systems vary from quiescent to 1 ‐ to 3‐day‐imbibed cotyledons. By labelling an endogenous globulin with 125 I a sensitive radiometric assay allowed the identification of both an acidic and a neutral proteolytic system in the quiescent cotyledon. Within the quiescent seed there already exists a high potential for initiating proteolysis, so that the requirement for proteolysis by specific endopeptidases synthesized de novo upon imbibition only applies to part of the reserve proteins.