L. Dolan et al., AN AGP EPITOPE DISTINGUISHES A CENTRAL METAXYLEM INITIAL FROM OTHER VASCULAR INITIALS IN THE ARABIDOPSIS ROOT, Protoplasma, 189(3-4), 1995, pp. 149-155
The developmental expression of an arabinogalactan protein (AGP) recog
nised by a monoclonal antibody, JIM 13, is described in Arabidopsis ro
ots. It is expressed in the single initial of the central metaxylem ve
ssel that lies immediately above the four central cells of the quiesce
nt centre. AGP expression spreads in a non-clonal fashion to neighbour
ing cell files as they mature. The AGP first appears in other pre-meta
xylem elements and subsequently in the layer of parenchyma cells on ei
ther side of the xylem axis. Later, it spreads to the entire ring of e
ight endodermal cell files and to those pericycle cell files next to t
he xylem pole. It is postulated that this epitope reflects an underlyi
ng set of cell signalling events that may be involved in defining loca
l positional values of cells important in establishing cellular patter
ns in the root.