Biological activities of native and synthetic IbHypSys
peptides. A, the change in pH of the medium of suspension
cultured tomato cells in response to increasing concentrations of
IbHypSys IV, when compared with H20 controls. The pH was
recorded 30 min after adding 10 μl of the peptide solution to 1 ml of
suspension cultured tomato cells. B, expression of
IbpreproHypSys and sporamin in excised sweet potato leaves supplied
for 2 h with 2.5 nm native (Nat.) IbHypSys or 25
μm synthetic (Syn.) IbHypSys IV, assayed by
RT-PCR. The expression of actin was used as an internal control. Leaves
supplied with water alone (H2O) were assayed as a
reference. The data shown are from a representative experiment from three
replications. C, sporamin expression levels induced in sweet potato
leaves fed synthetic IbHypSysIV analogs. IbHypSysIV and
synthetic analogs were dissolved in distilled H2Oata concentration
of 25 μm and supplied to excised leaves for 2 h as described
under “Experimental Procedures.” IbHypSysIV minus the
N-terminal arginine (-R1), IbHypSysIV with
alanine substituted for arginine at the amino terminus
(R1→A1) The expression levels of
sporamin were estimated using RT-PCR with actin as an internal control. Data
represent three replications. Error bars indicate standard error of
the mean. D, the induction of sporamin by synthetic peptides (see
“Experimental Procedures”). Excised young sweet potato leaves were
supplied with 25 μm of each synthetic peptide or water for 2 h,
and the expression levels of sporamin were estimated using RT-PCR, with actin
as an internal control.