TRANSFORMED HAIRY ROOTS OF MESEMBRYANTHEMUM-CRYSTALLINUM - GENE-EXPRESSION PATTERNS UPON SALT STRESS

In Mesembryanthemum crystallinum L. (common ice plant), salinity initi ates a series of events that contribute to increases in osmotically ac tive metabolites and the establishment of water conserving Crassulacea n Acid Metabolism. To better understand the role of isolated root-spec ific responses during salt stress, a vigorously growing root culture w as needed. Thus, we took advantage of the ability of Agrobacterium rhi zogenes to transform and generate growing hairy roots. Treatment of th e morphologically similar hairy and nontransformed roots of whole plan ts with 400 mM NaCl caused an 8-fold increase in proline levels in the se tissues. A heat shock protein 70 cognate, isolated from a root spec ific cDNA library, was also present at simlar levels in unstressed and stressed samples of both types of roots. However, the steady state ab undance of 6 other root cDNAs differed dramatically between transforme d hairy and normal roots in response to salt stress. These observation s suggest that several responses to salt stress are conserved between roots of whole plants and hairy roots. Additionally, a portion of tran scripts reacting to sail stress may be modulated by other factors excl usive to A. rhizogenes transformed hairy root growth. The complex and hierarchical environmental stress response of this halophyte relies on several tissue-specific interactions, and these responses are most ac curately characterized in whole plant tissues.