Analysis of gene expression from fbn5-1 T-DNA insertion mutant of Arabidopsis. Arabidopsis thaliana

We used microarrays to detail the global programme of gene expression underlying cellularisation and identified distinct classes of up-regulated genes in fbn5-1 T-DNA insertion Arabidopsis mutant. Fibrillins are lipid-associated proteins in plastids and are ubiquitous in plants. Fibrillins are known to accumulate and sequester carotenoids in chromoplasts during the development of flowers and fruits; however, little is known about the function of fibrillins in leaf tissues. Here we identified a novel protein fibrillin5 (FBN5) that is essential for plastoquinone-9 (PQ-9) biosynthesis in Arabidopsis thaliana. We showed that homozygous fbn5-1 plants were seedling-lethal, and XVE:FBN5-B transgenic plants expressing low levels of FBN5-B showed a lower growth rate and were smaller than wild-type. In chloroplasts, FBN5-B physically interacts with solanesyl-diphosphate synthase (SPS) 1 and 2, which synthesize the solanesyl moiety of PQ-9. Plants containing defective FBN5-B accumulated less PQ-9 and its cyclized product, plastochromanol-8, which is consistent with mutant phenotypes showing lower photosynthetic performance and higher levels of hydrogen peroxide. The role of FBN5-B in the FBN5-B/dimeric SPS complex is discussed with respect to biosynthesis of the solanesyl moiety. Overall design: 4 replicats of wild-type as control and fbn5-1 T-DNA insertion mutants were analized.

我们使用微阵列（microarrays）技术解析了细胞化进程背后的全局基因表达程序，并在fbn5-1 T-DNA插入拟南芥（Arabidopsis thaliana）突变体中鉴定出上调表达的不同基因类别。原纤蛋白（fibrillins）是质体中与脂质结合的蛋白质，广泛分布于植物体内。已知原纤蛋白在花与果实发育过程中，可在有色体中积累并隔离类胡萝卜素，但目前对其在叶片组织中的功能仍知之甚少。本研究鉴定出一种新型原纤蛋白5（FBN5），其为拟南芥质体醌-9（plastoquinone-9, PQ-9）生物合成所必需。研究发现，纯合fbn5-1植株为幼苗致死型；而低水平表达FBN5-B的XVE:FBN5-B转基因植株，其生长速率更低、体型较野生型更小。在叶绿体中，FBN5-B可与合成PQ-9茄尼基基团的茄尼基焦磷酸合酶（solanesyl-diphosphate synthase, SPS）1和2发生物理互作。携带缺陷型FBN5-B的植株中，PQ-9及其环化产物质体色醇-8（plastochromanol-8）的积累量更低，这与突变体光合性能下降、过氧化氢水平升高的表型相符。本文就FBN5-B在FBN5-B/二聚体SPS复合物中的作用，结合茄尼基基团的生物合成进行了探讨。整体实验设计：以野生型植株和fbn5-1 T-DNA插入突变体各设置4次生物学重复进行分析。