Abstract: As a part of the metallo\|β\|lactamase （MBL） superfamily， tRNA 3′\|end maturation is a process through which the 3′\|trailer sequence of precursor tRNAs （pre\|tRNAs） is removed. Compared with microbe and animals， there are fewer reports on tRNase Z in plants. Then we analyzed tRNase Z homologous proteins in 10 plants whose whole genome sequencing have been completed. It appeared that plants contained multiple distinct tRNase Zs predicted to reside in different subcellular compartments. Furthermore， while the bacterial\|type tRNase ZSs are present only in basal land plants and green algae， the eukaryotic\|type tRNase ZL and TM\|type tRNase ZSs are widespread in plants. The protein sequences of the TM\|type tRNase ZSs identified in plants are similar to those of the bacterial\|type tRNase ZSs, but have distinct features， including the TM\|type flexible arm， the variant catalytic HEAT and HST motifs， and a lack of the PxKxRN motif. By prediction of flowering plant tRNase ZSs， we found that TM\|type tRNase ZSs had a chloroplast signal sequence. Furthermore， while we analyzed the tRNase Z sequences， we mined some tRNase Z\|like proteins in basal land palnts and green algae. Our results revealed that the tRNase Z was more various in plants than fungi and animal. We thus expanded the TM\|type tRNase ZS family in plant and firstly predicted tRNase ZL\|like protein.

Key words: plant, TM\, type tRNase ZS, multiple sequence alignment, targeting sequences