OSMOTIC-STRESS ACTIVATED EXPRESSION OF AN ARABIDOPSIS PLASMA MEMBRANE-ASSOCIATED PROTEIN - SEQUENCE AND PREDICTED SECONDARY STRUCTURE

A cDNA clone At.MAMI (Arabidopsis thaliana membrane-associated mannito l-induced) was isolated from an Arabidopsis cDNA expression library by immunoselection. The cDNA was full-length (1.18 kb) with an open read ing frame of 798 nucleotides encoding a 265 amino acid protein. The se quence of At.MAMI did not show any significant identity with other gen es, as well as the deduced amino acid sequence with other proteins. Ho wever, prediction methods for the secondary structure of MAMI-30, toge ther with homologous domains revealed some identity with VAP-33, a pro tein involved in membrane trafficking in neuronal tissues. In contrast to VAP-33, MAMI-30 did not exhibit a transmembrane domain, but positi vely charged loop regions could be involved in membrane anchoring. Ind eed, MAMI-30 was immunodetected in purified plasma membrane from Arabi dopsis cells. The gene was responsive to low turgor in Arabidopsis and its expression regulated developmentally. In addition, reduction of t urgor caused a higher accumulation of mRNAs. (C) 1997 Elsevier Science B.V.