In:
Plant Physiology, Oxford University Press (OUP), Vol. 136, No. 4 ( 2004-12-01), p. 4237-4245
Abstract:
Hexadeca 7,10,13-trienoic acid (16:3Δ7,10,13) is one of the most abundant fatty acids in Arabidopsis (Arabidopsis thaliana) and a functional component of thylakoid membranes, where it is found as an sn-2 ester of monogalactosyldiacylglycerol. The Arabidopsis fad5 mutant lacks activity of the plastidial palmitoyl-monogalactosyldiacylglycerol Δ7-desaturase FAD5, and is characterized biochemically by the absence of 16:3Δ7,10,13 and physiologically by reduced chlorophyll content and a reduced recovery rate after photoinhibition. While the fad5 mutation has been mapped, the FAD5 gene was not unambiguously identified, and a formal functional characterization by complementation of fad5 mutant phenotypes has not been reported. Two candidate genes (At3g15850 and At3g15870) predicted to encode plastid-targeted desaturases at the fad5 chromosomal locus were cloned from fad5 plants and sequenced. A nonsense mutation changing codon TGG (Trp-98) into TGA (stop) was identified in At3g15850 (ADS3), whereas the fad5 At3g15870 allele was identical to wild type (after correction of a sequencing error in the published wild-type genomic At3g15870 sequence). Expression of a genomic clone or cDNA for wild-type At3g15850 conferred on fad5 plants the ability to synthesize 16:3Δ7,10,13 and restored leaf chlorophyll content. Arabidopsis carrying a T-DNA insertion in At3g15870 had wild-type levels of both 16:3Δ7,10,13 and chlorophyll. Together, these data formally prove that At3g15850 is FAD5. Interestingly, the fad5 phenotype was partially complemented when extraplastidial Δ9-desaturases of the Arabidopsis desaturase (ADS) family were expressed as fusions with a plastidial transit peptide. Tight correlation between leaf 16:3Δ7,10,13 levels and chlorophyll content suggests a role for plastidial fatty acid desaturases in thylakoid formation.
Type of Medium:
Online Resource
ISSN:
1532-2548
,
0032-0889
DOI:
10.1104/pp.104.052951
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2004
detail.hit.zdb_id:
2004346-6
detail.hit.zdb_id:
208914-2
SSG:
12
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