Blue Light and Transcription

In a recent lengthy review with the general title of The Effect of Light on RNA and Protein Synthesis in Plants [23], only the relationship between light absorbed by the phytochrome system and the synthesis of RNA was covered. Does this mean that the crytochrome2 and other even less well understood blue light, nonphytochromal acceptor systems, have nothing to do with RNA synthesis? How much can/will this review rectify the situation? I shall try to analyze the direct and indirect evidence that has accumulated where blue light is implicated in affecting transcription. We shall have to ask some questions about relating the blue syndrome with transcription: (1) Is RNA synthesis really necessary? It has been a basic premise of developmental biologists that induced changes in developmental patterns require new transcriptional patterns. But do we need transcription for a transient phototropic response? Are not translational or activity controls sufficient? (2) How good are the data supporting transcriptional changes? Indirect evidence, especially with inhibitors, must not be fully accepted as conclusive, even after weighing the known drawbacks. (3)Do we have evidence for speccificity; distinct transcriptional products rate or “step-up” will bring concurrent increases in all RNA species; can be processes be separated? How closely is the photoact linked to transcriptional events? Is transcriptional many steps down the line from photoreception or are the processes tightly and closely coupled in sequence?