Rice (Oryza sativa) endosperm accumulates a massive amount of storage starch and storage proteins during seed development. However, little is known about the regulatory system involved in the production of storage substances. The rice flo2 mutation resulted in reduced grain size and starch quality. Map-based cloning identified FLOURY ENDOSPERM2 (FLO2), a member of a novel gene family conserved in plants, as the gene responsible for the rice flo2 mutation. FLO2 harbors a tetratricopeptide repeat motif, considered to mediate a protein-protein interactions. FLO2 was abundantly expressed in developing seeds coincident with production of storage starch and protein, as well as in leaves, while abundant expression of its homologs was observed only in leaves. The flo2 mutation decreased expression of genes involved in production of storage starch and storage proteins in the endosperm. Differences between cultivars in their responsiveness of FLO2 expression during high-temperature stress indicated that FLO2 may be involved in heat tolerance during seed development. Overexpression of FLO2 enlarged the size of grains significantly. These results suggest that FLO2 plays a pivotal regulatory role in rice grain size and starch quality by affecting storage substance accumulation in the endosperm.

Physical exercise is a good means of enhancing and maintaining health. However, many people struggle to make exercise be a habit, in part because of the associated fatigue. The present study investigated the effects of tomato juice on fatigue induced by exercise in humans and mice. A study of 10 healthy men and women indicated that drinking tomato juice suppressed post-exercise increases in rated perceived exertion, a subjective fatigue indicator. In mice, a single administration of tomato juice significantly attenuated exercise-induced fatigue, as measured by locomotor activity and blood transforming growth factor β and corticosterone levels. The active substances in tomatoes, which were among the aqueous components as of tomato juice supernatant, showed the same anti-fatigue effects as whole tomato juice. Moreover, these effects were mimicked by water supplemented with the aqueous components (i.e., sugars, organic acids, and amino acids) and were likely exerted by two or more of these components. Our results suggest that consuming tomato juice prior to or during an exercise session can reduce post-exercise fatigue, which could encourage more individuals to incorporate a regular exercise regimen into their daily routine.

Synthesis of storage starch and protein accumulation is the main action of endosperm organogenesis in term of the economic importance of rice. This event is strongly disturbed by abiotic stresses such as high temperature; thus, the upcoming global warming will cause a crisis with a great impact on food production^1,2^. The enzymes for the protein storage and starch synthesis pathway should work in concert to carry out the organogenesis of rice endosperm^3-5^, but the regulatory mechanism is largely unknown. Here we show that a novel regulatory factor, named OsCEO1, acts as the conductor of endosperm organogenesis during the rice grain filling stage. The physiological properties of floury-endosperm-2 (flo2) mutants showed many similarities to symptoms of grains developed under high-temperature conditions, suggesting important roles of the responsible gene in sensitivity to high-temperature stress. Our map-based cloning identified the responsible gene for the flo2 mutant, OsCEO1, which has no homology to any genes of known function. The OsCEO1 belongs to a novel conserved gene family and encodes a protein composed of 1,720 amino acid residues containing a TPR (tetratricopeptide repeat) motif, which is considered to mediate a protein-protein interaction. The yeast two-hybrid analysis raised an unknown protein showing homology to a late embryogenesis abundant protein and a putative basic helix-loop-helix protein as candidates for the direct interactor for OsCEO1, whereas no enzyme genes for the synthesis of storage substances were detected. The flo2 mutant exhibited reduced expression of several genes for putative regulatory proteins as well as many enzymes involved in storage starch and proteins. These results suggest that OsCEO1 is a superior conductor of the novel regulatory cascade of endosperm organogenesis and may have important roles in the response to high-temperature stress.

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