Early embryogenesis in Pisum sativum L.
The temporal and spatial patterns of differential legA expression during early Pisum embryogenesis have been examined. An in situ hybridisation protocol has been empirically refined to allow analysis of low level legA expression, at the mRNA level, whilst ELISA and immunocytochemistry have been used to examine both protein levels and spatial distribution within the early seed. Low levels of legK mRNA were detected in very early globular embryos which were present at 4-5 d.a.f. High levels of legK expression were detected in the transient endosperm tissue at both the mRNA and protein level. High levels of expression, at the mRNA level, were also detected within the suspensor, although a similar level of expression at the protein level was not detected. It is proposed that legA expression within both the endosperm and suspensor is of nutritional significance for the development of the embryo. Comparison of legA mRNA and protein localisation studies, at later stages of embryo development, demonstrated a very strong correlation, both quantitatively and spatially, between mRNA and protein levels, indicating the importance of transcription level regulation in the control of differential legA expression. A cDNA complementary to a mRNA species present at elevated levels in Pisum root was used to examine embryonic root (radicle) ontogeny. The mRNA species was found to be absent from embryonic root, however its presence in primary roots of seedlings four days post imbibition has been demonstrated.