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

Protein changes associated with hormonal regulation of lateralroot initiation in lettuce (Lactuca sativa L.) roots were examined.Naphthalene acetic acid (NAA) stimulates the induction of lateralroots (Maclsaac, Sawhney, and Pohorecky, 1989) and this wasaccompanied by an increase in soluble proteins as well as thesynthesis of several polypeptides, including specific polypeptidesof 32 and 31 kD. The synthesis of these polypeptides coincidedwith the onset of cell division in the pericycle of NAA-treatedroots. Application of cycloheximide at different times showedthat NAA-induced protein synthesis is essential for the initiationand development of lateral root primordia. Kinetin inhibitedthe formation of lateral roots as well as the level of solubleproteins in NAA-treated roots. In addition, kinetin-treatedroots contained 22 and 21 kD polypeptides not found in othertreatments. This study suggests that the mechanisms of NAA-stimulationand kinetin-inhibition of lateral root initiation are probablydifferent. Key words: Lactuca sativa, lateral roots, proteins