Localisation and development of proteolytic activities in quinoa (Chenopodium quinoa) seeds during germination and early seedling growth

Abstract

Quinoa (Chenopodium quinoa) is an Andean seed used in a similar manner to cereals. Its seeds are perispermic with an endosperm present only in the micropylar region. The storage globulins are mainly deposited in the embryo. In this study, the development of proteolytic activities and protein profiles were studied in these tissues during germination and early growth. The endosperm was highly proteolytic with a 60-fold activity compared to the embryo. This endosperm activity consisted of 100% cysteine-proteases, and increased until 24 h after imbibition (hai). The activities found in the embryo consisted of aspartic, serine and metallo-proteases, but remained nearly unchanged over the course of growth. The bulk of seed proteins were found in the embryo globulin fraction with electrophoretic mobilities corresponding to molecular weights of 49 and 57 k, that started fading 48 hai. The presence of abscisic acid led to a lower proteolytic activity in the endosperm, and increased the percentage of abnormally germinating seeds. The protease activities found in the endosperm are not likely to be significant for storage protein mobilisation as the majority of the storage proteins are located in the embryo. These data suggest they may have a role in endosperm weakening during germination.