Abstract
Metallocarboxypeptidases are metal-dependent enzymes, whose biological activity is regulated by inhibitors directed on the metal-containing active site. Some metallocarboxypeptidase inhibitors are induced under stress conditions and have a role in defense against pests. This paper is aimed at investigating the response of the tomato metallocarboxypeptidase inhibitor (TCMP)-1 to Cd and other abiotic stresses. To this aim, the tomato TCMP-1 was ectopically expressed in the model species Arabidopsis thaliana, and a yeast two-hybrid analysis was performed to identify interacting proteins. We demonstrate that TCMP-1 is responsive to Cd, NaCl, and abscisic acid (ABA) and interacts with the tomato heavy metal-associated isoprenylated plant protein (HIPP)26. A. thaliana plants overexpressing TCMP-1 accumulate lower amount of Cd in shoots, display an increased expression of AtHIPP26 in comparison with wild-type plants, and are characterized by a modulation in the expression of antioxidant enzymes. Overall, these results suggest a possible role for the TCMP-1/HIPP26 complex in Cd response and compartmentalization.
Highlights
Protease inhibitors (PIs) are an heterogenous group of molecules widely distributed in different organisms, such as bacteria, fungi, animals, and plants
A phylogenetic analysis conducted on five characterized metallocarboxypeptidase inhibitors of Nicotiana tabacum (NtMCPIa and NtMCPIb), Solanum tuberosum (StPCI), and Solanum lycopersicum (SlTCMP-1 and SlTCMP-2), revealed that NtMCPIa and NtMCPIb are more closely related to SlTCMP-1 and StPCI, while SlTCMP-2 (Solyc07g049140) constitutes a separate branch (Figure 1a, left)
Considering that NtMCPIa and NtMCPIb transcripts were found to be differentially expressed in leaf trichomes after Cd treatment [17], we decided to monitor their expression pattern in leaves collected from three-week-old tobacco plants grown in hydroponics and treated with 10 μM CdSO4 for 24 and 72 h (Figure 1b)
Summary
Protease inhibitors (PIs) are an heterogenous group of molecules widely distributed in different organisms, such as bacteria, fungi, animals, and plants. PIs are crucial components for cellular homeostasis and survival, and participate in several physiological processes, such as the mobilization of storage proteins in seeds, the regulation of endogenous enzymatic activities, and the protection against pests [2,3]. In addition to proteins with higher molecular mass such as serpins, the PI group comprises small/medium range polypeptides (
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