As softening and color change are the most easily detectable
aspects of the ripening syndrome in fruits, a few genes known to
be involved in such processes were also examined in the
sarcotesta of Magnolia seeds. As regards softening, two partial
cDNAs coding for different expansins (MgEXP1 and MgEXP2)
were cloned. MgEXP1 showed maximum transcript accumulation
in the very young sarcotesta, followed by the fully ripe one;
transcripts were always observed in seeds deprived of their
sarcotesta, with an increase during the early stages of seed growth
followed by a decrease in late samples, in which growth was
complete (Fig. 4A). MgEXP2 showed a clearly defined ripeningspecific
pattern of expression, with transcripts steadily increasing
from white to ripe red sarcotesta and undetectable levels in fully
ripe ones. Transcripts in seeds without their sarcotesta could not
be detected at any stage of development (Fig. 4B).