Interestingly, the synthesis of non starch polysaccharides appears to be significantly retarded because of the down regulation of related genes such as cellulose synthase and the up regulation of genes for degrading hemicellulose and pectin. inhibitor Sorafenib Therefore, the synthesis of cell wall related sugar might be sacrificed in CSSL50 1. In light of the impor tance of normal synthesis of starch and related polysac charides, it is very likely that disorders in the enzyme activity and the expression of genes responsible for these events are among the major causes for endosperm chalkiness in CSSL50 1. Potential roles of ROS in rice grain chalkiness formation Reactive oxygen species are partially reduced forms of atmospheric oxygen.
They typically result from the excitation of O2 to form singlet oxygen or from the transfer of one, two or three electrons to O2 to form, respectively, a superoxide radical, hydrogen peroxide or a hydroxyl radical. Among them, H2O2 is one of the most stable ROS. With both reducing and oxidizing properties, H2O2 has effects on almost all organisms, and can influence the life of every single cell. On one hand, H2O2 is highly reactive and toxic, and can lead to oxidative destruction of cells, on the other hand, it acts as a signaling mole cule in regulating cell growth and development, cell pro liferation, cell stress response, and signal transduction. When accumulated at high enough concentrations, H2O2 can directly or indirectly oxidize enough of the cellular ascorbic acid and glutathione pool to alter the overall redox state of the cells.
Such high concentrations of H2O2 can also damage a large variety of biomolecules such as lipids, proteins and nucleic acids that are essen tial for the activity and integrity of the cells. As sessile organisms, plants have evolved a high degree of developmental plasticity to optimize their growth and reproduction in response to various biotic and abiotic stresses. Under these conditions, the excessive H2O2 is efficiently scavenged by various antioxidative defense mechanisms in plant cells. The major ROS scavenging enzymes include ascorbate peroxidase, catalase, superoxide dismutase, glu tathione peroxidase, monodehydroascorbate reductase, Glutaredoxin and peroxire doxin. Together with the antioxidants ascorbic acid and glutathione, these enzymes provide plant cells with highly efficient machinery for detoxifying H2O2 and other ROS.
In the present study, the expression levels of five genes involved in reactive oxygen species production and hemeostasis including superoxide dismutase, ascorbate peroxidase, glutathione peroxidase, monodehydroascorbate reductase and peroxiredoxin were found to be higher in CSSL50 1 than those in Asominori, suggesting that Brefeldin_A the antioxidative network in CSSL50 1 is activated. This result is consis tent with the higher concentration of H2O2 in CSSL50 1.