Mobilization of seed protein reserves

Abstract

The mobilization of seed storage proteins upon seed imbibition and germination is a crucial process in the establishment of the seedling. Storage proteins fold compactly, presenting only a few vulnerable regions for initial proteolytic digestion. Evolutionarily related storage proteins have similar three-dimensional structure, and thus tend to be initially cleaved at similar sites. The initial cleavage makes possible subsequent rapid and extensive breakdown catalyzed by endo- and exopeptidases. The proteolytic enzymes that degrade the storage proteins during mobilization identified so far are mostly cysteine proteases, but also include serine, aspartic and metalloproteases. Plants often ensure early initiation of storage protein mobilization by depositing active proteases during seed maturation, in the very compartments where storage proteins are sequestered. Various means are used in such cases to prevent proteolytic attack until after imbibition of the seed with water. This constraint, however, is not always enforced as the dry seeds of some plant species contain proteolytic intermediates as a result of limited proteolysis of some storage proteins. Besides addressing fundamental questions in plant protein metabolism, studies of the mobilization of storage proteins will point out proteolytic events to avoid in large-scale production of cloned products in seeds. Conversely, proteolytic enzymes may be applied toward reduction of food allergens, many of which are seed storage proteins.

Protein Bodies in Cotyledon Cells Exhibit Differential Patterns of Legumin-Like Proteins Mobilization during Seedling Germinating States

“…Upon seed germination, s substantial proteolysis of SSPs provides the necessary amino acids to accomplish different physiological processes during plant development [7,9,10].…”

“…These are complex and multi-stages processes of developing plants, for which efficiency of reserve mobilization, and hence of seedling establishment itself, depends on the extent of reserve accumulation during seed development and maturation [8]. SSP degradation takes place after a (long) period of rest when seeds germinate and seedlings start growing, and where all these proteins are mobilized to nourish the seedling for plant development [2,9]. Moreover, the major metabolic events occurring during seed germination are different depending of the specie, as well as their genetically determined diversity seed morphology, physiological maturity, developmental pattern and chemical reserves [2,10,11].…”

Quantification of storage proteins during seed imbibition of native species from the brazilian caatinga vegetation

“…Proteins in seeds have the major function of nitrogen supply to the embryo and seedling in its early stage of development. The synthesis of these proteins is regulated during seed development and is tissuespecific, i.e., they are only synthesised in seed tissues and are not found in any other tissues except for lecithin (globulin), which can be found at the tips of growing roots (TAN-WILSON;WILSON, 2012). The synthesis of protein is extremely important during germination.…”

“…For seedling recruitment, the mobilisation of storage proteins is crucial during imbibition and seed germination (TAN-WILSON, WILSON, 2012). Osborne (1924) classified the seed storage proteins based on their solubility in different solvents.…”

Estudo proteômico de variedades de milho (<i>Zea mays</i> L.) obtidas por melhoramento clássico e por recombinação genética

“…As proteínas de armazenamento são as proteínas mais comumente identificadas em sementes de plantas. Elas fornecem uma parte importante da nutrição necessária para a germinação de sementes e crescimento de plântulas (TAN-WILSON;WILSON, 2012;WANG et al, 2014). Estudos prévios têm observado o acúmulo e utilização destas proteínas ao longo do desenvolvimento de sementes através da análise proteômica (GALLARDO et al, 2007;HUANG et al, 2012;WANG et al, 2014).…”