CLONING OF GENES WHOSE EXPRESSION IS CORRELATED WITH MITOSIS AND LOCALIZED IN DIVIDING CELLS IN ROOT CAPS OF PISUM-SATIVUM L

Removal of border cells from pea roots synchronizes and induces root c ap cell division, wall biogenesis and differentiation. Three messages which are expressed differentially in such induced root caps have been cloned. Sequence analyses showed that the PsHRGP1-encoded protein has high homology with a hydroxyproline-rich glycoprotein. The PsCaP23-en coded protein has high homology with an alfalfa callus protein or tran slationally controlled human or mouse tumor protein P23. The PsRbL41-e ncoded protein has high homology with a highly basic 60S ribosomal pro tein L41. in situ hybridization showed that PsHRGP1, PsCaP23 and PsRbL 41 messages are localized within dividing cells of the root cap. PsHRG P1 is highly expressed in uninduced root caps, but its message is repr essed by 10-11 times as soon as cell division and differentiation begi n. Expression of PsHRGP1 recovers to higher than (180%) its initial le vel in 30 min. PsHRGP1 is root-specific. PsCaP23 and PsRbL41 messages increase ca. 3-fold within 15 min after root cap induction. All three genes represent small families of 3-5 closely related genes in the pea genome.