NACL-INDUCED ALTERATIONS IN BOTH CELL STRUCTURE AND TISSUE-SPECIFIC PLASMA-MEMBRANE H-ATPASE GENE-EXPRESSION()

NaCl-induced plasma membrane H+-ATPase gene expression, which occurs i n roots and fully expanded leaves of the halophyte Atriplex nummularia L. (X. Niu, M.L. Narasimhan, R.A. Salzman, R.A. Bressan, P.M. Hasegaw a [1993] Plant Physiol 103: 713-718), has been differentially localize d to specific tissues using in situ RNA hybridization techniques. Twen ty-four-hour exposure of plants to 400 mM NaCl resulted in substantial accumulation of H+ pump message in the epidermis of the root tip and the endodermis of the root elongation/differentiation zone. In expande d leaves, NaCl induction of plasma membrane H+-ATPase message accumula tion was localized to bundle-sheath cells. Ultrastructural analyses in dicated that significant cytological adaptations in root cells include d plasmolysis that is accompanied by plasma membrane invaginations, fo rmation of Hechtian strands and vesiculation, and vacuolation. These r esults identify specific tissues that are involved in the regulation o f Na+ and Cl- uptake into different organs of the halophyte A. nummula ria and provide evidence of the intercellular and interorgan coordinat ion that occurs in the mediation of NaCl adaptation.