Cytokinin, Light, and “Developmental Control” of Protein Synthesis in Cucurbita Cotyledons

Abstract

AbstractCotyledons detached from pumpkin seedlings of different stages of development were either illuminated or treated with 4.10−5 M cytokinin (benzyladenine, BA) in darkness. Comparison of the abilities to incorporate 14C‐leucine into proteins in vivo as well as 35S‐methionine in vitro by means of an RNA‐programmed cell‐free wheat germ system demonstrates that the patterns of the two‐dimensionally separated in vivo labelled soluble proteins are very similar in differently developed or treated cotyledons. Although the translatable mRNA patterns were almost identical in qualitative respect, our data do not exclude the appearance of a few minor polypeptides altered by either illumination or BA treatment. The steady‐state levels of the mRNAs in cotyledons from 12 days old seedlings were remarkably similar irrespective of cotyledon treatment (water, BA, light) and resemble those levels obtained with illuminated or BA‐treated cotyledons of earlier seedlings stages. Our results suggest that the amount of abundant (soluble) proteins in pumpkin cotyledons is developmentally regulated mainly at the transcript level. Extrinsic factors such as cytokinins (BA) or light are equally able to accelerate the developmental program of gene expression in early‐detached cotyledons, which are probably deficient in endogenous hormone.