Rice Genetics IV - IRRI books - International Rice Research Institute

Cell divisionCell elongationand expansionProminent expansionAcidosis(shown by neutral red)TonoplastdisruptionPlasma membrane destruction(shown by Evans blue staining)Cell collapseCell collapse inradial directionCell file formation First cell death Expansion of porosity7thCortex1stFig. 1. A proposed model of the processes leading to cortical cell death in riceroots.Cell cycle genes in rice: essential componentsfor sustainable cell proliferationCyclin-dependent protein kinases (CDKs) are serine/threonine protein kinases thatare involved in the regulation of the eukaryotic cell cycle. A single major CDK hasbeen identified in the fission yeast Schizosaccharomyces pombe (CDC2) and in thebudding yeast Saccharomyces cerevisiae (CDC28). However, the growing list of CDKsin human cells suggests that, during development, each CDK in metazoans plays aspecific role at a specific time in the cell cycle. CDKs are activated by the binding ofcyclins and phosphorylation (Morgan 1995). Each CDK interacts with a specific subsetof cyclins, and the size of this subset varies among CDKs. For example, CDC28can associate with many different cyclins, whereas human CDC2 interacts with relativelyfew (Nigg 1995). A short conserved amino acid sequence, PSTAIRE, in CDKsis responsible for the binding of cyclins, which activate CDKs by changing the conformationat the catalytic site (Jeffrey et al 1995, Morgan 1996). These cyclins alsofunction in the targeting of CDKs to specific substrates or subcellular locations(Hoffmann et al 1993).Plants also express different kinds of CDK and multiple genes for CDKs havebeen found in Arabidopsis, alfalfa, rice, soybean, maize, and Antirrhinum. A correla-Molecular dissection of cell death in rice 369