Kunitz proteinase inhibitors in legumes
have mainly been described as defence and storage
proteins. Here, we report a Kunitz trypsin inhibitor,
encoded by the CaTPI-1 gene from Cicer arietinum.
The transcription of this gene mainly occurs in seedling
vegetative organs, and is aVected by the light and
growth stages. The recombinant TPI-1 protein
expressed in E. coli was seen to be an eYcient inhibitor
of trypsin. After the generation of polyclonal antibodies
against recombinant TPI-1 protein, the protein was
located in the cell wall of elongating epicotyls and radicles
by Western-blot experiments, in agreement with
the transcription pattern. These results, together with
the fact that both CaTPI-1 mRNA and protein levels
decreased with epicotyl growth, suggest a possible role
in the elongation of seedling epicotyls and radicles.
Immunolocalization analyses of the TPI-1 protein indicated
that it is abundant in the cell walls of both immature
primary xylem cells and surrounding parenchyma
cells. This location has led us to explore potential functions
for TPI-1 protein in vascular tissue during seedling
elongation.
