Investigating the role of tasselseed1 and silkless1 in the sex determination process of maize.

摘要

The sex determination pathway of maize is a developmental cascade leading to the formation of unisexual flowers. Unisexuality in maize is controlled by a tasselseed-mediated cell death process of pistils in staminate florets and a gibberellic acid (GA)-mediated cell arrest of stamens in pistillate florets. This thesis describes (a) the positional cloning and functional characterization of the sex determination gene tasselseed1 (ts1), and (b) the positional cloning of the silkless1 (sk1) gene. Chapter 1 introduces the genetics and molecular biology of the sex determination pathway in maize. Chapter 2 presents a map-based cloning approach to identify the ts1 gene and its confirmation by characterizing a mutant allelic series. Analysis of the TS1 amino acid sequence predicts that TS1 is a class 2 lipoxygenase with 13-LOX regiospecificity, leading to the hypothesis that TS1 may be involved in the biosynthesis of the plant hormone jasmonic acid (JA). Chapter 3 examines this hypothesis by investigating the expression, localization and biochemical properties of TS1. These studies show that TS1 is localized to plastids and is necessary for the synthesis of JA, which may signal the pistil abortion process in maize. Chapter 4 describes the cloning of a physical interval of ∼700 Kb containing the sk1 gene and 11 predicted genes that represent sk1 candidates. Further work is required to identify the sk1 gene through characterization of a mutant series. Finally, Chapter 5 discusses the findings of this work in relation to jasmonate-regulated development and the processes of pistil abortion and pistil cell protection in maize, and proposes new hypothesis to guide future work.