Poster: Tropisms

Abs # 668: Immunolocalization of two different annexins in gravistimulated Arabidopsis seedlings: correlations with secretion

Presenter:	Clark, Greg , gclark@ccwf.cc.utexas.edu
Authors	Clark, Greg  (A)   Dauwalder, Marianne  (A)   Lee, Dongwoo  (A)   Barry, John  (A)   Roux, Stanley  (A)
Affiliations:	(A): University of Texas at Austin

Annexins are a multigene, multifunctional family of calcium-dependent, membrane-binding proteins found in animal and plant cells. In previous studies, we have localized annexins in secretory cell types especially at the cell periphery, including the extreme tips of polarly growing cells. In Arabidopsis there are eight different annexin cDNAs, which range from 30% to 64% in deduced amino acid sequence identity. The two most similar Arabidopsis annexins, AnnAt1 and AnnAt2, contain a region within the third structural repeat that is fairly divergent. From this region two different 31-mer peptides were synthesized and then used as antigens to raise polyclonal antibodies. These two monospecific Arabidopsis annexin antibodies and a previously characterized pea annexin antibody were used for immunolocalization experiments. Autoradiographic studies of H³-galactose incorporation were also used to follow secretion levels. Initial localization results in seedlings obtained using the two monospecific Arabidopsis antibodies showed staining of secretory cells including epidermal cells and showed good correlation with previously published RNA in situ hybridization results. H³-galactose incorporation patterns clearly demonstrate that regions of active secretion can be correlated with regions of strong annexin staining. To further test this correlation seedlings were gravistimulated for various lengths of time and then analyzed with the same procedures. Preliminary results show some asymmetric localization of annexins in both shoots and roots with the higher levels on the faster growing side in each case. Initial analysis of H³-galactose incorporation also shows parallel asymmetry. Results from these experiments will be presented and discussed. (Supported by NASA: NAG2- 1586).