The chloroplast F 1 F o -ATP synthase/ATPase (cpATPase) couples ATP synthesis to the light-driven electrochemical proton gradient. The cpATPase is a multiprotein complex and consists of a membrane-spanning protein channel (comprising subunit types a, b, b9, and c) and a peripheral domain (subunits a, b, g, d, and «). We report the characterization of the Arabidopsis (Arabidopsis thaliana) CONSERVED ONLY IN THE GREEN LINEAGE160 (AtCGL160) protein (AtCGL160), conserved in green algae and plants. AtCGL160 is an integral thylakoid protein, and its carboxyl-terminal portion is distantly related to prokaryotic ATP SYNTHASE PROTEIN1 (Atp1/UncI) proteins that are thought to function in ATP synthase assembly. Plants without AtCGL160 display an increase in xanthophyll cycle activity and energy-dependent nonphotochemical quenching. These photosynthetic perturbations can be attributed to a severe reduction in cpATPase levels that result in increased acidification of the thylakoid lumen. AtCGL160 is not an integral cpATPase component but is specifically required for the efficient incorporation of the c-subunit into the cpATPase. AtCGL160, as well as a chimeric protein containing the amino-terminal part of AtCGL160 and Synechocystis sp. PCC6803 Atp1, physically interact with the c-subunit. We conclude that AtCGL160 and Atp1 facilitate the assembly of the membranous part of the cpATPase in their hosts, but loss of their functions provokes a unique compensatory response in each organism.
A solid phase microextraction sampling method using pencil-lead fibre coupled with gas chromatography-mass spectrometry was used to monitor the organic volatile compounds of the roots, leaves and gum of Astragalus compactus. Under optimised conditions, a range of volatile compounds were recognised in different parts of A. compactus. Based on the results obtained, the nature and level of the volatiles vary in distinct parts of the plant. In comparison with other Astragalus species investigated, only one volatile organochlorine compound, tetradecane,1-chloro, was identified in roots. Intriguingly, the toxic chlorinated component was not detectable in the gum samples. These findings highlight the higher quality of the gum of A. compactus compared to the gums of some other Astragalus species, which are reported to be contaminated with chlorinated components.
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