Contrapuntal Networks of Gene Expression during Arabidopsis Seed Filling[W]

Abstract

We have used cDNA microarrays to examine changes in gene expression during Arabidopsis seed development and to compare wild-type and mutant wrinkled1 ( wri1 ) seeds that have an 80% reduction in oil. Between 5 and 13 days after flowering, a period preceding and including the major accumulation of storage oils and proteins, ‫ف‬ 35% of the genes represented on the array changed at least twofold, but a larger fraction (65%) showed little or no change in expression. Genes whose expression changed most tended to be expressed more in seeds than in other tissues. Genes related to the biosynthesis of storage components showed several distinct temporal expression patterns. For example, a number of genes encoding core fatty acid synthesis enzymes displayed a bell-shaped pattern of expression between 5 and 13 days after flowering. By contrast, the expression of storage proteins, oleosins, and other known abscisic acid-regulated genes increased later and remained high. Genes for photosynthetic proteins followed a pattern very similar to that of fatty acid synthesis proteins, implicating a role in CO 2 refixation and the supply of cofactors for oil synthesis. Expression profiles of key carbon transporters and glycolytic enzymes reflected shifts in flux from cytosolic to plastid metabolism. Despite major changes in metabolism between wri1 and wild-type seeds, Ͻ 1% of genes differed by more than twofold, and most of these were involved in central lipid and carbohydrate metabolism. Thus, these data define in part the downstream responses to disruption of the WRI1 gene.

Compartmentation of Triacylglycerol Accumulation in Plants

“…Transcriptional profiling of oil palm mesocarp revealed Ͼ50-fold higher WRI1 expression levels compared with date palm mesocarp, a closely related species that contains no oil (13). Consistent with data in developing seeds (14), genes encoding machinery for FA biosynthesis and pyruvate supply are up-regulated substantially in oil palm (an average of Ͼ13-fold) (15). The direct precursor of carbon for FA synthesis is pyruvate in most oil-synthesizing tissues, and a plastidial pyruvate dehydrogenase (PDH) supplies acetyl-CoA for ACCase.…”

The Predicted Candidates of Arabidopsis Plastid Inner Envelope Membrane Proteins and Their Expression Profiles,

“…Changes in transcript abundance in seeds during 5 to 13 d after flowering were recently reported by Ruuska et al (2002). Twenty-six AtPEM candidates changed more than 2-fold during this period (data not shown).…”

“…To further investigate the tissue-specific gene expression pattern of AtPEM candidates, we analyzed publicly available cDNA microarray data from the Stanford Microarray Database (SMD; http://genomewww.stanford.edu/microarray; Sherlock et al, 2001) and from the Arabidopsis developing seed array Web site (http://www.bpp.msu.edu/Seed/SeedArray.htm; Girke et al, 2000;Ruuska et al, 2002). Expression profiles of 230 AtPEM candidates for about 110 different microarray experiments were found in the SMD public domain (as of March 12, 2002).…”

Probing in Vivo Metabolism by Stable Isotope Labeling of Storage Lipids and Proteins in Developing Brassica napusEmbryos

“…This is suggested by the fact that during embryo development of B. napus embryos, the Suc to hexose ratio in the endosperm liquid increases (see Table I; King et al, 1997). With the increase of Suc concentration in the endosperm liquid and the onset of storage product accumulation, induction of Suc synthase is reported in seeds of B. napus (King et al, 1997) and induction of Suc synthase mRNA and a Suc transporter mRNA are observed in seeds of Arabidopsis (Ruuska et al, 2002). Thus, the relative ratio of uptake of [U-13 C 6 ]Glc and Suc may change during embryo development.…”