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Role of the low-molecular-weight subunits PetL, PetG, and PetN in assembly, stability, and dimerization of the cytochrome b6f complex in tobacco.

Abstract：

:The cytochrome b(6)f (Cyt b(6)f) complex in flowering plants contains nine conserved subunits, of which three, PetG, PetL, and PetN, are bitopic plastid-encoded low-molecular-weight proteins of largely unknown function. Homoplastomic knockout lines of the three genes have been generated in tobacco (Nicotiana tabacum 'Petit Havana') to analyze and compare their roles in assembly and stability of the complex. Deletion of petG or petN caused a bleached phenotype and loss of photosynthetic electron transport and photoautotrophy. Levels of all subunits that constitute the Cyt b(6)f complex were faintly detectable, indicating that both proteins are essential for the stability of the membrane complex. In contrast, DeltapetL plants accumulate about 50% of other Cyt b(6)f subunits, appear green, and grow photoautotrophically. However, DeltapetL plants show increased light sensitivity as compared to wild type. Assembly studies revealed that PetL is primarily required for proper conformation of the Rieske protein, leading to stability and formation of dimeric Cyt b(6)f complexes. Unlike wild type, phosphorylation levels of the outer antenna of photosystem II (PSII) are significantly decreased under state II conditions, although the plastoquinone pool is largely reduced in DeltapetL, as revealed by measurements of PSI and PSII redox states. This confirms the sensory role of the Cyt b(6)f complex in activation of the corresponding kinase. The reduced light-harvesting complex II phosphorylation did not affect state transition and association of light-harvesting complex II to PSI under state II conditions. Ferredoxin-dependent plastoquinone reduction, which functions in cyclic electron transport around PSI in vivo, was not impaired in DeltapetL.

journal_name

Plant Physiol

journal_title

Plant physiology

authors

Schwenkert S,Legen J,Takami T,Shikanai T,Herrmann RG,Meurer J

doi

10.1104/pp.107.100131

subject

Has Abstract

pub_date

2007-08-01 00:00:00

pages

1924-35

issue

eissn

0032-0889

issn

1532-2548

pii

pp.107.100131

journal_volume

144

pub_type

杂志文章

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Role of the low-molecular-weight subunits PetL, PetG, and PetN in assembly, stability, and dimerization of the cytochrome b6f complex in tobacco.