Comportamento da Lectina de sementes de Canavalia brasiliensis Mart. durante a germinação em presença de luz

Abstract

RESUMO -A comparação da metabolização da lectina de Cana valia hrasiliensis com as demais proteínas de reservas durante a germinação das sementes na presença de luz foi acompanhada através da combinação de dosagem de proteínas solú-veis, determinação da atividade hemaglutinante, cromatografia de afinidade em coluna de Sephadex G-50 e eletroforese em gel de poliacrilamida em presença de dodecilsulfato de sódio (SDS) e 2-mercaptoetanol. Os resultados foram comparados com resultados anteriormente obtidos com sementes germinadas na ausência da luz e ficou evidenciado que, mesmo com as plântulas fotossintetizando , a lectina de Canavalia brasiliensis é preservada, sendo metabolizada após as, demais proteínas de reserva. Estes dados sugerem também que estas proteínas devam ter funções específicas durante o ciclo vital da planta e não se constituem apenas em proteín5~s de reserva. 'Palavras-chave: Lectinas, Canavalia brasiliensis, germinação.ABSTRACT -Canavalia brasiliensis seed lectin during germination in the presence of light. The mobilization of the lectin of Canavalia brasiliensis during se~d germination, in the presence of light, was studied in comparison with the reserve proteins. Methods employed were determination of soluble protein con tent, hemagglutinating acti vi ty , affinity chromatography on Sephadex G-50 column , and PAGE-SDS. The results showed that the lectin was metabolized later than the reserve proteins suggesting that it may have a special function other than a simple reserve protein.

Carbohydrate/glycan-binding specificity of legume lectins in respect to their proposed biological functions

“…The search to determine the exactly moment of appearance of the lectin in protein bodies during the development of seeds should be appreciated in the attempt to establish if a parallelism exists between storage protein deposition and lectin appearance in the establishment of protein bodies. The results from our studies with Diocleinae lectins during seeds germination showed that the mobilization of these glucose/mannose specific lectins are always retarded when compared to storage proteins, independently, of the seedlings being grown in presence or absence of light (Moreira & Cavada, 1984;Cavada et al, 1990;Cavada et al, 1994). Indeed, traces of these lectins could be detected until the last day of examined germination, when a small amount of other proteins were present in cotyledons (Cavada et al, 1994).…”

“…Indeed, traces of these lectins could be detected until the last day of examined germination, when a small amount of other proteins were present in cotyledons (Cavada et al, 1994). When germinated in the light, again, seed lectins were preserved although high molecular weight proteins were mobilized to establish the seedlings (Cavada et al,1990). During maturation of Canavalia brasiliensis seeds, the lectin was detected only after high molecular weight protein appearance .…”

Lectins from Pisum arvense seeds behave differently from storage proteins during germination in the darkness

“…Experiments to evaluate lectins and the other seed proteins in order to speculate about their functions in seed germination are not scarce in the literature (Causse andRougé, 1983;Cavada et al, 1990;Cavada et al, 1994;Oliveira et al, 1998). This strategy seems to be common, although limited in itself, since lectins are judged as ordinary proteins.…”

“…However, results from immunochemical and electrophoretic studies are useful to compare the lectin and seed storage proteins in some aspects. Therefore, we used the experience and the results of our previous studies, with the seed lectins from Canavalia brasiliensis (Cavada et al, 1990) and Dioclea guianensis, subtribe Diocleinae (Cavada et al,1994) to investigate the mobilization of the lectin from Pisum arvense during germination.…”

“…Based on this information, it has been suggested that these proteins should be seed storage proteins involved in amino acid supply during seed germination and seedling growth. However, studies carried out by Moreira andCavada (1984), Cavada et al (1990) and Cavada et al (1994) are not in agreement with this hypothesis, based upon seed germination studies that have compared the mobilization of storage proteins and the behaviour of the lectins during the germination process. In the present report we advance the idea that, although accumulated in protein bodies, the legume lectins have a different behavior from classical high molecular mass storage proteins and that the lectins should play a more relevant role in seedling establishment.…”