Characterization of Several Heterodera glycines mRNA that Encode Small Proteins with Putative Signal Peptides

Two subtraction libraries were prepared from RNA extracted at early and late stages in the development of soybean cyst nematodes (SCN), Heterodera glycines, in soybean roots. The cDNA from inoculated roots were subtracted with cDNA prepared from non-inoculated roots and SCN eggs, and 384 clones from each library were sequenced. BLAST searches revealed that 191 of the cDNA in the late library were most probably of nematode origin. Alignment of the 191 sequences produced 28 unigenes and 1 singlet. The size of the transcripts for the nematode genes was confirmed by RNA blot hybridization. Thirteen SCN transcripts were selected for further study because they included short open reading frames encoding predicted proteins of <20 kDa with signal peptides at their amino-terminus. Ten of the 13 encode predicted peptides <10 kDa. Although most of the 13 transcripts were fairly abundant in the SCN dbEST, most were of unknown function based on BLAST similarities. Nevertheless, several had characteristics common to anti-microbial peptides, and in situ hybridization indicated that three of the selected transcripts were expressed in the female reproductive system.