Transcriptional and post-transcriptional regulation of storage protein gene expression in sulfur-deficient pea seeds

We have used in vitro transcription in isolated pea nuclei to determine whether the expression of genes for the seed storage proteins legumin and vicilin is regulated transcriptionally or post-transcriptionally in response to changing sulfur status in the developing seed. During the first 48 h of recovery from S deficiency, transcription of legumin genes increased by two-fold whereas the level of legumin mRNA increased 20-fold in the same period. Vicilin gene transcription decreased during recovery, consistent with a gradual decrease in mRNA levels. We conclude that regulation of legumin mRNA levels in response to changing S status is post-transcriptional, whereas that of vicilin mRNA is transcriptional. In contrast, during normal plant development the expression of both of these gene families appears to be under transcriptional control.