Control of Cell Death in Rice Male Reproductive Development

In higher plants, timely degradation of tapetal cells, the innermost sporophytic cells of the anther wall layer, is a prerequisite for the development of viable pollen grains. We use the tapetal cells as the model to investigate the mechanism underlying programmed cell death in monocot rice (Oryza sativa). We revealed several key regulators such as Tapetum Degeneration Retardation (TDR), PERSISTENT TAPETAL CELL 1 (PTC1), MADS3 and MICROSPORE AND TAPETUM REGULATOR 1 (MTR1) in controlling tapetal cell death. TDR positively triggers by activating the expression of a cysteine protease gene OsCP1. PTC1 controls a conserved switch for programmed tapetal development and degradation, ptc1 displays necrosis-like uncontrolled tapetal cell death. The rice floral homeotic C-class gene, MADS3, regulates late anther development and pollen formation by maintaining reactive oxygen species (ROS) homeostasis. MTR1 encoding a fasciclin domain protein and is specifically expressed in the male reproductive cells, but it is able to affect both tapetal cell death and microspore development, suggesting it’s critical role in coordinating the development of reproductive cells and their adjacent somatic cells. We also investigate the regulatory network of these regulators in programmed male reproductive development in rice.