Toward Molecular Understanding of In Vitro and In Planta Shoot Organogenesis

Abstract

Shoot organogenesis, one of the in vitro plant regeneration processes that occur during in vitro micropropagation, is used in the study of plant development. Morphological, physiological, and molecular aspects of in vitro shoot organogenesis have been extensively studied for over 50 years. Because of the research progress in plant genetics and molecular biology, our understanding of in planta and in vitro shoot meristem development, the cell cycle and cytokinin signal transduction has advanced significantly. These research advances provide useful information as well as molecular tools to study further the genetic and molecular aspects of shoot organogenesis. A number of key molecular markers, genes, and pathways have been shown to play a critical role in the process of in vitro shoot organogenesis. Furthermore, these studies reveal that in vitro shoot organogenesis, as with in planta shoot development, is a complex, well-coordinated developmental process, given that the induction of a single molecular event is likely to be insufficient to induce the entire process. Continued study is required to identify additional molecular events that trigger dedifferentiation and act as developmental switches for de novo shoot development.

*This article is dedicated to the memory of Shibo Zhang, who continues to inspire our interests in this topic.

Keywords:

• auxin
• cell cycle
• cytokinin
• dedifferentiation
• development
• in vitro organogenesis
• shoot apical meristem

ACKNOWLEDGMENTS

We dedicate this review to the memory of Dr. Shibo Zhang, whose life goal was to understand the molecular pathways involved in in vitro shoot development. Although his death in a tragic accident prevented completion of his dream, we are sure that he would be pleased with the progress made in this field. We are grateful to Barbara Alonso for helping to prepare the manuscript. We attempted to cite all pertinent work but apologize for any citations that were inadvertently missed.

Notes

*This article is dedicated to the memory of Shibo Zhang, who continues to inspire our interests in this topic.