Here, we report the identification and characterization of CaTPI-2, which is
a member of a Cicer arietinum gene family encoding Kunitz-type proteinase
inhibitors with at least two members –CaTPI-1 and CaTPI-2. The widespread
mRNA accumulation of CaTPI-2 in all the different organs of 4-day-old
etiolated seedlings and in stem internodes differs from the more specific Cicer
arietinum Trypsin Proteinase Inhibitor-1 (CaTPI-1) transcription. After the
generation of polyclonal antibodies against the recombinant Trypsin Proteinase
Inhibitor-2 (TPI-2) protein, the protein was located in the cell walls of
vegetative organs. The decrease found in both transcription and TPI-2 protein
levels when the epicotyls aged, together with the wider and more intensive
immunostaining of the protein in apical zones of epicotyls and radicles, in
consonance with their higher elongation rate, indicated a relationship of the
TPI-2 protein with the elongation process. CaTPI-2 mRNA levels were
increased by wounding in both epicotyls and leaves. The accumulation of
CaTPI-2 mRNA in seedlings, which was further amplified by mechanical
wounding in epicotyls and leaves, suggests the involvement of TPI-2 in the
response to wounds. Our results indicate that TPI-2 protein has features
different from those of the former characterized Trypsin Proteinase Inhibitor-1
(TPI-1), such as its different gene regulation under light, a different cellular
location and its upregulation by wounding, which implies a function different
from that of TPI-1 in chickpea metabolism.
