Phytochrome as the Primary Photoregulator of the Synthesis of Calvin Cycle Enzymes in Etiolated Pea Seedlings

Abstract

MORPHOGENETIC changes induced by red light (660 nm) and mediated by the pigment-protein phytochrome are well documented^1,2. Less is known, however, about phytochrome-mediated effects of red light at the cellular level. We show here that red light induces the development of etiolated apices of pea stems and that one consequence of this development is the net synthesis of a plastid-localized protein, namely fraction I protein, and an increase in its associated enzyme activity, ribulose-1,5-bisphosphate (RuDP) carboxylase³. Two other enzymes of the Calvin cycle show similar increases in activity. The magnitude of these increases and their reversibility by irradiation with far-red light (730 nm) implicates phytochrome rather than protochlorophyllide as the primary photoregulator of the synthesis of these enzymes.