CYTOSOLIC ASCORBATE PEROXIDASE FROM ARABIDOPSIS-THALIANA L IS ENCODEDBY A SMALL MULTIGENE FAMILY

A second cytosolic ascorbate peroxidase (cAPX; EC 1.11.1.11) gene from Arabidopsis thaliana has been characterised. This second gene (design ated APX1b) maps to linkage group 3 and potentially encodes a cAPX as closely related to that from other dicotyledonous species as to the ot her member of this gene family (Kubo et al,, 1993, FEES Lett 315: 313- 317; here designated APX1a), which maps to linkage group 1. In contras t, the lack of sequence similarity in non-coding regions of the genes implies that they are differentially regulated. Under non-stressed con ditions only APX1a is expressed. APX1b was identified during low-strin gency probing using a cDNA coding for pea cAPX which, in turn, was rec overed from a cDNA library by immunoscreening with an antiserum raised against tea plastidial APX (pAPX). No pAPX cDNAs were recovered, desp ite the antiserum displaying specificity for pAPX in Western blots.