Inheritance of Seed Shattering in Lolium temulentum and L. persicum Hybrids

Lolium temulentum and L. persicum are non-crop species found in wheat and barley fields. L. temulentum has non-shattering seeds like the associated grain crops, whereas L. persicum seeds shatter after maturity. We analyzed the inheritance mode of shattering tendency by comparing the F₂ of L. temulentum and L. persicum hybrids. The selfed progeny of L. temulentum and L. persicum exhibited typical non-shattering (1.6% shattering) and shattering phenotypes (70.8%), respectively. F₁ hybrids of L. temulentum×L. persicum and its reciprocals were of the shattering phenotype (71.4% and 63.8%, respectively), indicating that shattering is dominant to non-shattering. When the phenotype ratio was assumed to be 15 shattering: 1 non-shattering, the χ² value for F₂ segregation was not significant at the 5% level, and the reciprocal effect was not detected. This indicates that the non-shattering tendency is controlled by two recessive genes. The two-gene inheritance model of shattering tendency suggests that harvest is the selector for seed shattering in cultivated fields, thus the alternative tendency for non-shattering seeds of L. temulentum or shattering of L. persicum would be better adapted to cultivated fields.     

Asef, a link between the tumor suppressor APC and G-protein signaling

The adenomatous polyposis coli gene (APC) is mutated in familial adenomatous polyposis and in sporadic colorectal tumors. Here the APC gene product is shown to bind through its armadillo repeat domain to a Rac-specific guanine nucleotide exchange factor (GEF), termed Asef. Endogenous APC colocalized with Asef in mouse colon epithelial cells and neuronal cells. Furthermore, APC enhanced the GEF activity of Asef and stimulated Asef-mediated cell flattening, membrane ruffling, and lamellipodia formation in MDCK cells. These results suggest that the APC-Asef complex may regulate the actin cytoskeletal network, cell morphology and migration, and neuronal function.     

An SNP caused loss of seed shattering during rice domestication

Loss of seed shattering was a key event in the domestication of major cereals. We revealed that the qSH1 gene, a major quantitative trait locus of seed shattering in rice, encodes a BEL1-type homeobox gene and demonstrated that a single-nucleotide polymorphism (SNP) in the 5' regulatory region of the qSH1 gene caused loss of seed shattering owing to the absence of abscission layer formation. Haplotype analysis and association analysis in various rice collections revealed that the SNP was highly associated with shattering among japonica subspecies of rice, implying that it was a target of artificial selection during rice domestication.