The concept of the sexual reproduction cycle and its evolutionary significance.

Shu-Nong Bai

doi:10.3389/fpls.2015.00011

Abstract

The concept of a “sexual reproduction cycle (SRC)” was first proposed by Bai and Xu (2013) to describe the integration of meiosis, sex differentiation, and fertilization. This review discusses the evolutionary and scientific implications of considering these three events as part of a single process. Viewed in this way, the SRC is revealed to be a mechanism for efficiently increasing genetic variation, facilitating adaptation to environmental challenges. It also becomes clear that, in terms of cell proliferation, it is appropriate to contrast mitosis with the entire SRC, rather than with meiosis alone. Evolutionarily, it appears that the SRC was first established in unicellular eukaryotes and that all multicellular organisms evolved within that framework. This concept provides a new perspective into how sexual reproduction evolved, how generations should be defined, and how developmental processes of various multicellular organisms should properly be compared.

Highlights

The concept of a “sexual reproduction cycle (SRC)” was first proposed by Bai and Xu (2013) to describe the integration of meiosis, sex differentiation, and fertilization
Studies on sex determination in plants have focused on regulation of unisexual flower development (Ainsworth, 1999; Bai and Xu, 2013) since plant sex was defined based on unisexual flowers by Robbins and Pearson (1933), i.e., “a flower or plant is male if it bears only stamen and that is female if it bears only pistils.”
To understand the regulatory mechanism of sex differentiation, following the concept originated from Robbins and Pearson (1933), we have investigated the regulation of unisexual flower development using cucumber for more than a decade

Summary

Introduction

The concept of a “sexual reproduction cycle (SRC)” was first proposed by Bai and Xu (2013) to describe the integration of meiosis, sex differentiation, and fertilization. We hypothesized that before multicellular organisms emerged, a process called the sexual reproduction cycle (SRC) evolved based on the existing mitotic cell cycle in unicellular eukaryotes. Regardless of the presence or absence of germlines, e.g., in animals or plants, respectively, (Evens and Walbot, 2003), new generations in all multicellular organisms are generated through sexual reproduction consisting of the three key events: meiosis, sex differentiation, and fertilization.

Results

Conclusion