Protein Changes Associated with Auxin-Induced Stimulation and Kinetin-Induced Inhibition of Lateral Root Initiation in Lettuce (Lactuca sativa) Roots

Abstract

Protein changes associated with hormonal regulation of lateral root initiation in lettuce (Lactuca sativa L.) roots were examined. Naphthalene acetic acid (NAA) stimulates the induction of lateral roots (Maclsaac, Sawhney, and Pohorecky, 1989) and this was accompanied by an increase in soluble proteins as well as the synthesis of several polypeptides, including specific polypeptides of 32 and 31 kD. The synthesis of these polypeptides coincided with the onset of cell division in the pericycle of NAA-treated roots. Application of cycloheximide at different times showed that NAA-induced protein synthesis is essential for the initiation and development of lateral root primordia. Kinetin inhibited the formation of lateral roots as well as the level of soluble proteins in NAA-treated roots. In addition, kinetin-treated roots contained 22 and 21 kD polypeptides not found in other treatments. This study suggests that the mechanisms of NAA-stimulation and kinetin-inhibition of lateral root initiation are probably different.