The genome of the japonica subspecies of rice, an important cereal and model monocot, was sequenced and assembled by whole-genome shotgun sequencing. The assembled sequence covers 93% of the 420-megabase genome. Gene predictions on the assembled sequence suggest that the genome contains 32,000 to 50,000 genes. Homologs of 98% of the known maize, wheat, and barley proteins are found in rice. Synteny and gene homology between rice and the other cereal genomes are extensive, whereas synteny with Arabidopsis is limited. Assignment of candidate rice orthologs to Arabidopsis genes is possible in many cases. The rice genome sequence provides a foundation for the improvement of cereals, our most important crops.

We have produced a draft sequence of the rice genome for the most widely cultivated subspecies in China, Oryza sativa L. ssp. indica, by whole-genome shotgun sequencing. The genome was 466 megabases in size, with an estimated 46,022 to 55,615 genes. Functional coverage in the assembled sequences was 92.0%. About 42.2% of the genome was in exact 20-nucleotide oligomer repeats, and most of the transposons were in the intergenic regions between genes. Although 80.6% of predicted Arabidopsis thaliana genes had a homolog in rice, only 49.4% of predicted rice genes had a homolog in A. thaliana. The large proportion of rice genes with no recognizable homologs is due to a gradient in the GC content of rice coding sequences.

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Binding of vinculin to adhesion plaque proteins is restricted by an intramolecular association of vinculin's head and tail regions. Results of previous work suggest that polyphosphoinositides disrupt this interaction and thereby promote binding of vinculin to both talin and actin. However, data presented here show that phosphatidylinositol 4,5-bisphosphate (PI4,5P 2 ) inhibits the interaction of purified tail domain with F-actin. Upon re-examining the effect of PI4,5P 2 on the actin and talinbinding activities of intact vinculin, we find that when the experimental design controls for the effect of magnesium on aggregation of PI4,5P 2 micelles, polyphosphoinositides promote interactions with the talin-binding domain, but block interactions of the actin-binding domain. In contrast, if vinculin is trapped in an open confirmation by a peptide specific for the talin-binding domain of vinculin, actin binding is allowed. These results demonstrate that activation of the actin-binding activity of vinculin requires steps other than or in addition to the binding of PI4,5P 2 .Vinculin, a 117-kDa component of microfilament-associated cell junctions (1), is a modular protein composed of a 95-kDa N-terminal, globular head domain connected by a short prolinerich region to a 30-kDa tail domain (reviewed in Ref.2). Vinculin has an essential role in embryogenesis (3, 4) and regulatory roles in adhesion, spreading, and motility of cells in culture (5-10). Vinculin probably functions by interacting with particular structural and regulatory proteins found at focal contacts and zonulae adherens (11). Biochemical experiments with purified proteins show that the binding sites on vinculin for talin (12), F-actin (13), acidic phospholipids (14), and vasodilator-stimulated phosphoprotein (15), and sites for protein kinase C-mediated phosphorylation (16,17), are blocked by the intramolecular association (K d ϳ 50 nM) of the head (V h ) and tail (V t ) regions (12). Therefore, regulation of the head-tail interaction to expose cryptic ligand binding and regulatory sites is hypothesized to be critical for recruitment of vinculin to sites of cell adhesion and/or for vinculin-dependent assembly of focal adhesion complexes (13). Elucidation of the factors that regulate the head-tail interaction is central to understanding how events at the cell surface are expressed ultimately in the activities of molecules directly responsible for the functions of focal adhesion plaques.Evidence from in vitro experiments shows that acidic phospholipids in general (16), or specifically PI4,5P 2 1 (18) block the interaction of purified head and tail domains and act on intact vinculin to expose the binding sites for talin on V h (18) and for F-actin on V t (16,18). This observation provides a mechanistic link between cell surface receptors that modulate the synthesis of PI4,5P 2 , a signaling molecule (19) and vinculin, a structural molecule involved in assembling a focal adhesion plaque and mediating anchorage to the actin cytoskeleton.Here we provide new informat...

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