Selection of Arabidopsis genes encoding secreted and plasma membrane proteins

Secreted and plasma membrane proteins play crucial roles in a variety of ph ysiological and developmental processes of multicellular organisms. Systema tic cloning of the genes encoding these proteins is therefore of general in terest. An effective method of trapping signal sequences was first describe d by Tashiro et al. (1993), and a similar yet more efficient method was rep orted by Klein et al. (1996) and Jacobs et al. (1997). In this study, we ca rried out the latter yeast-based signal sequence trap to clone genes from A rabidopsis thaliana encoding secreted and plasma membrane proteins. Of 144 sequenced cDNA clones, 18% are identical to previously cloned Arabidopsis t haliana genes, 12% are homologous to genes identified from various organism s, and 46% are novel. All of the isolated genes identical or homologous to previously reported genes are either secreted or plasma membrane proteins, and the remaining novel genes appear to contain functional signal sequences based on computer-aided sequence analysis. The full-length cDNA clones of one homologous gene and another novel gene were isolated and sequenced. The deduced amino acid sequences suggest that the former encodes a secreted pr otein, and the latter encodes a type 1 membrane protein. These results indi cate that the signal sequence trap method is effective and useful for the i solation of plant genes encoding secreted and plasma membrane proteins.