Autonomy to plant growth regulators and gene expression in periwinkle cultures in vitro

To better understand the effect of habituation on gene expression in plant cells, we have compared the accumulation of specific mRNAs encoding respect ively two proline-rich proteins, a chaperone protein and three enzymes link ing primary and secondary metabolisms in two models of in vitro culture of periwinkle. These models consisted of two couples of a 2,4-dichlorophenoxya cetic acid-dependent/2,4-dichlorophenoxyacetic acid independent line in whi ch autonomy to auxin and cytokinin was obtained either through habituation or through transformation with the isopentenyltransferase gene from Agrobac terium tumefaciens. Results showed that gene expression was modified by pla nt growth regulator autonomy but differently according to the type of auton omy: only the gene encoding a hydroxyproline-rich glycoprotein was regulate d similarly in both PGR-independent lines. On the other hand, PGR autonomy did not lead to total insensitivity to exogenously-applied PGRs, and the tw o PGR autonomous lines did not accumulate indole alkaloids for different re asons.