Female Control of Reproductive Success in Arabidopsis thaliana

In flowering plants, successful pollination is important for sexual reproduction. It involves a series of intercellular communication pathways between male and female tissues. This cell-cell communication includes the attraction and reception of the male gametophyte, or pollen tube (PT), by the synergid cells of the female gametophyte, also known as the embryo sac (ES). To achieve reproductive success, it is important to manipulate reproduction at both quality and quantity levels. In other words, flowering plants can only produce as many seeds as they produce ovules and these ovules must be able to be fertilized to make seeds. In Arabidopsis thaliana, NORTIA (NTA), a member of the MILDEW RESISTANCE LOCUS O (MLO) family of proteins, plays a critical role in the communication process that regulates PT reception. Upon PT arrival at the filiform apparatus, NTAbecomes polarly redistributed from the Golgi-associated compartment to the filiform apparatus of the synergid cell, indicating that PT-triggered regulation of the synergid secretory system is important for synergid function during pollination. In the first part of this dissertation, I will describe my research of the female controlled reproductive success at molecular and cell biology level with a focus on NTA. Moreover, the ovules contain the female gametophytes which are fertilized during pollination to initiate seed development. Thus, ovule development is an essential and crucial process during plant growth. More importantly, the number of ovules will limit the quantity of reproductive success. However, the major regulators are still poorly understood. The remaining chapters of my dissertation describethe identification of key components that affect the number of ovules during plant development by using natural variation in Arabidopsis thaliana and the correlations of ovule number with flowering time. Discovering new ovule number regulators could provide new tools for improving the agricultural productivity.