Biology Reference
In-Depth Information
CHAPTER FIVE
Vegetative Phase Change
and Shoot Maturation in Plants
R. Scott Poethig
1
Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
1
Corresponding author: e-mail address: spoethig@sas.upenn.edu
Contents
1.
Introduction
126
2. Terminology
126
3. Heteroblasty and Vegetative Phase Change
127
4. miR156 and miR157: Master Regulators of Vegetative Phase Change
129
5. miR156 Targets
130
6. Molecular Insights into the Phenomenology of Vegetative Phase Change
134
6.1 How are vegetative phases specified?
134
6.2 The relationship between vegetative and reproductive maturation
135
6.3 How is timing of vegetative phase change regulated?
139
7. Conclusion
144
Acknowledgments
144
References
144
Abstract
As a plant shoot develops, it produces different types of leaves, buds, and internodes,
and eventually acquires the capacity to produce structures involved in sexual reproduc-
tion. Morphological and anatomical traits that change in coordinated fashion at a pre-
dictable time in vegetative development allow this process to be divided into several
more-or-less discrete phases; the transition between these phases is termed
“
vegetative
phase change.
”
Vegetative phase change is regulated by a decrease in the expression
of the related microRNAs, miR156, and miR157, which act by repressing the expression
of squamosa promoter binding protein/SBP-like (SBP/SPL) transcription factors. SBP/SPL
proteins regulate a wide variety of processes in shoot development, including flowering
time and inflorescence development. Answers to long-standing questions about the
relationship between vegetative and reproductive maturation have come from genetic
analyses of the transcriptional and posttranscriptional regulatory networks in which
these proteins are involved. Studies conducted over several decades indicate that car-
bohydrates have a significant effect on phase-specific leaf traits, and recent research
suggests that sugar may be the leaf signal that promotes vegetative phase change.
