Year-end Sale % OFF 
Abstract
Cyanide-resistant alternative oxidase (AOX) is a nuclear-encoded quinol oxidase located in the inner mitochondrial membrane. Although the quality control of AOX proteins is expected to have a role in elevated respiration in mitochondria, it remains unclear whether thermogenic plants possess molecular mechanisms for the mitochondrial degradation of AOX. To better understand the mechanism of AOX turnover in mitochondria, we performed a series of in organello AOX degradation assays using mitochondria from various stages of the appendices of Arum maculatum. Our analyses clearly indicated that AOX proteins at certain stages in the appendices are degraded at 30°C, which is close to the maximum appendix temperature observed during thermogenesis. Interestingly, such temperature-dependent protease activities were specifically inhibited by E-64, a cysteine protease inhibitor. Moreover, purification and subsequent nano LC–MS/MS analyses of E-64-sensitive and DCG-04-labeled active mitochondrial protease revealed an ∼30 kDa protein with an identical partial peptide sequence to the cysteine protease 1-like protein from Phoenix dactylifera. Our data collectively suggest that AOX is a potential target for temperature-dependent E-64-sensitive cysteine protease in the appendices of A. maculatum. A possible retrograde signalling cascade mediated by specific degradation of AOX proteins and its physiological significance are discussed.
Highlights
Thermogenesis in reproductive organs occurs in various seed plants including Araceae, Aristolochiaceae, Annonaceae, Cycadaceae, Cyclanthaceae, Magnoliaceae, Nelumbonaceae and Nymphaeaceae [1]
Because these non-hot samples acted as an experimental control by representing the physiological status at the boundary stages of thermogenesis, we decided to use them for subsequent comparative analyses of AmAOX gene transcript levels, and an in organello degradation assay of AmAOX proteins, alongside the pre-hot and hot appendices
These results suggested that reactive oxygen species (ROS) produced during thermogenesis in appendices are scavenged by anti-oxidative defence mechanisms in mitochondria, our DNP-based analysis could not determine the molecule-specific oxidation status of the mitochondrial proteins
Summary
Thermogenesis in reproductive organs occurs in various seed plants including Araceae, Aristolochiaceae, Annonaceae, Cycadaceae, Cyclanthaceae, Magnoliaceae, Nelumbonaceae and Nymphaeaceae [1]. Since the seminal report in 1955 [2] that mitochondria in the spadix of Arum maculatum, a thermogenic plant in Araceae, exhibit cyanide-insensitive respiration, significant progress has been made in establishing the structure-function relationships of cyanide-insensitive alternative oxidase (AOX). Thermogenesis in plants is attributed partially to the activity of AOX in the mitochondria [3,4,5,6,7,8,9]. AOX is part of an alternative respiratory pathway specific to plants as well as certain fungi and protists, which acts as an electron acceptor from ubiquinol, thereby bypassing complex III [9,10]. Respiratory analysis with mitochondria purified from thermogenic tissues has revealed a large cyanide-insensitive respiration capacity in A. maculatum [13,14,15], Symplocarpus renifolius [16], Nelumbo nucifera [17], Dracunculus vulgaris [18] and Cycas revoluta [19]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
