Grain-filling, an important trait that contributes greatly to grain weight, is regulated by quantitative trait loci and is associated with crop domestication syndrome. However, the genes and underlying molecular mechanisms controlling crop grain-filling remain elusive. Here we report the isolation and functional analysis of the rice GIF1 (GRAIN INCOMPLETE FILLING 1) gene that encodes a cell-wall invertase required for carbon partitioning during early grain-filling. The cultivated GIF1 gene shows a restricted expression pattern during grain-filling compared to the wild rice allele, probably a result of accumulated mutations in the gene's regulatory sequence through domestication. Fine mapping with introgression lines revealed that the wild rice GIF1 is responsible for grain weight reduction. Ectopic expression of the cultivated GIF1 gene with the 35S or rice Waxy promoter resulted in smaller grains, whereas overexpression of GIF1 driven by its native promoter increased grain production. These findings, together with the domestication signature that we identified by comparing nucleotide diversity of the GIF1 loci between cultivated and wild rice, strongly suggest that GIF1 is a potential domestication gene and that such a domestication-selected gene can be used for further crop improvement.

Severe weight loss and debilitative wasting of lean body mass frequently complicate the treatment of patients suffering from malignancy or chronic infection. Termed cachexia, this syndrome of anorexia, anemia, and weakness further increases cancer mortality; some data indicate that as many as 30% of cancer patients die from cachexia, rather than tumor burden (1-3). The severity of cachexia may be unrelated to tumor size or parasite load, and profound wasting has been observed in patients with tumor burdens of only 0.01-5.0% body mass (4). If not reversed, cachexia-associated derangements of homeostasis lead to immunological deficiencies, organ failure, and multiple metabolic abnormalities . While it is clear that a variety of mechanisms participate in the pathogenesis of cachexia, and that cachexia adversely affects prognosis, the etiology of this syndrome is not known.For a number of years we have been searching for endogenous, humoral mediators of cachexia, beginning with the characterization of metabolic changes in trypanosome-infected rabbits that develop profound cachexia and lose up to 50% of lean body mass within weeks. In later stages of disease a paradoxical increase in circulating triglycerides occurs, attributable to systemic suppression of lipoprotein lipase (LPL)t (5). A bacterial LPS-inducible serum factor which suppresses LPL in mice, and several other key lipogenic enzymes in the adipocyte cell line 3T3-L1, was isolated and named cachectin (6, 7). Cachectin evokes a state of cellular cachexia by suppressing the expression of several mRNAs encoding essential lipogenic enzymes (8, 9). Myocytes also show changes in cellular metabolism after exposure to cachectin in vitro, including a prompt decrease in resting transmembrane potential difference and depletion of intracellular glycogen stores with increased lactate efflux, and a later increase in hexose transporters (10,11). It has been suggested that cachectin may play a