The Impact of Chronic High Temperatures on Anther and Pollen Development in Cultivated Oryza Species

Rice is the leading staple for half the world’s population. Climate change, expanding populations and loss of agricultural land are projected to reduce rice yields by upwards of 30%. Significantly, rice yields decline by 10% for every 1°C increase in temperature. Temperatures ≥ 32°C can cause failure in male reproductive development and eliminate yields in some cultivars. This dissertation determined the developmental features and mechanisms associated with failure in male reproduction at temperatures of 32 °C and 36 °C in temperature tolerant and sensitive cultivars of O. sativa and O. glaberrima. Temperatures of 32 °C impaired anther dehiscence in the temperature sensitive cultivar of O. sativa by preventing septum cell wall degradation, which is essential for pollen dispersal. Temperatures of 36 °C induced abortion in pollen development either during meiosis primarily in O. sativa or at the uninucleate stage in O. glaberrima. Abortion during meiosis was associated with autophagic programmed cell death, whereas failure at the uninucleate stage of pollen development was associated with features of necrosis such as cytoplasmic shrinkage and cell wall collapse. Increased hydrogen peroxide production was detected in aborting meiocytes and uninucleate microspores at 36 °C, indicating that this reactive oxygen species may contribute to the failure of male reproductive development in rice during high temperature stress. Identification of the timing of failure in male reproductive development, and the cellular features associated with these processes in rice, form the basis for the identification of molecular mechanisms that control yield responses to high temperature stress.Ph