Cells of this zone have a stem cell function and are essential for meristem maintenance. The proliferation and growth rates at the meristem summit usually differ considerably from those at the periphery. Surrounding the central zone is the peripheral zone. The rate of cell division in the peripheral zone is higher than that of the central zone.
Peripheral zone cells give rise to cells which contribute to the organs of the plant, including leaves, inflorescence meristems, and floral meristems. An active apical meristem lays down a growing root or shoot behind itself, pushing itself forward. They are very small compared to the cylinder-shaped lateral meristems, and are composed of several layers, which varies according to plant type.
The outermost layer is called the tunica, while the innermost layers are cumulatively called the corpus. Meristem tissue and plant development Meristematic tissues are cells or group of cells that have the ability to divide. In this mutant, WUS expression is stimulated by cytokinin treatment in the same way as in wild-type plants.
However, in contrast to wild-type plants, mutant SAM morphology and CLV3 expression respond drastically to cytokinin treatment. These results suggest that the ER family regulates stem cell homeostasis by buffering its cytokinin responsiveness in the vegetative SAM.
Comparison of mono-, di- and tri-arabinosylated CLV3 glycopeptides revealed that biological activity increases progressively as arabinose chain length increases. Thus, the arabinose chain length of CLV3 is important for its biological activity. The authors analyzed the solution structure of arabinosylated CLV3 by nuclear magnetic resonance NMR spectroscopy: the arabinose chain of [Ara 3 ]CLV3 extends toward the C-terminal end of the peptide, and its non-reducing end is positioned proximal to the peptide backbone.
Thus, the arabinose chain causes distinct, highly directional distortion in the C-terminal half of the peptide. Takahashi et al. This result suggests that the AS1—AS2—ETT pathway plays a critical role in controlling the cell division cycle and in controlling the biosynthesis of cytokinin around the SAM, which stabilizes leaf development in Arabidopsis.
As mentioned above, auxin regulates both embryogenesis and post-embryonic organogenesis. Yoshida et al. Miyashima et al. Okumura et al. Previous studies of partial loss-of-function gnom alleles have revealed the role of GNOM in auxin transport-related, post-embryonic development including lateral root formation Geldner et al.
However, as these gnom alleles caused severe defects in auxin-regulated root and shoot development, it was unclear whether GNOM directly regulated lateral root initiation. The paper by Ohashi-Ito et al. Now that we know the basic framework of florigen action, the diverse roles of florigen and its active complex FAC have become an emerging topic.
In this SFI, two research papers address this new topic. Hiraoka et al. They showed that FT and TSF , respectively, play a major role in branch outgrowth in long-day and short-day conditions.
A similar differential contribution of the two genes in flowering has been reported previously Yamaguchi et al. Tsuji et al. Interestingly, the FAC involving OsFD2 seems to play a role in leaf development, suggesting that florigen plays different roles in rice when associated with different FACs. This SFI contains collaborative review papers from Dr. Pautler et al. They also discuss the roles of the CLV—WUS pathway and cytokinin in grass shoot meristem maintenance and organization during the vegetative phase.
The accompanying paper by Tanaka et al. The complex mechanisms that determine meristem identity, including branch, spikelet and flower meristems, are being unraveled using rice and maize mutants. These two review papers explain how grass shoot meristems can change their properties in response to intrinsic developmental cues and to environmental cues.
The variety of mechanisms of shoot meristem homeostasis in monocots and dicots is also discussed. Over recent decades, advances in molecular genetic and biochemical approaches have allowed us to unravel some of the mechanisms of plant development.
The post-genomic era now enables us to investigate essentially all the genes in the genomes of model plants, thereby enhancing our understanding of their functions in growth and developmental processes.
Further unraveling of molecular cascades in developmental events will reveal the crucial roles of many as yet unidentified regulators including TFs, miRNAs, small peptides, receptor-like kinases and other signaling molecules. Two examples of this are described in this SFI. Shinohara and Matsubayashi demonstrate the importance of arabinosylation for the activity of CLV3 peptides, while Miyashima et al. To understand fully the mechanisms underlying plant development, we will need to understand both the spatio-temporal regulation and the function of such key molecules, by combining advanced imaging techniques with an understanding of the structural biology of molecular complexes and biochemistry.
A good example is the recent identification of the FAC Taoka et al. Studies of the molecular mechanisms of formative cell division and of the epigenetic regulation of developmentally critical genes of plants should shed light on the development of the plant, a unique multicellular system with cell walls. The post-genomic era also enables us to expand the list of model plants to include basal land plants mosses and liverworts. Comparative studies based on Arabidopsis, rice and other species will help us to understand plant development in a broad evolutionary perspective.
We hope that the papers in this SFI will provide readers of this journal with some new ideas and insights into plant development and will inspire researchers to open up new research fields in this area. We wish to acknowledge the authors and reviewers who have greatly contributed to this issue. Google Scholar. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.
Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation.
Volume Carbon Cycling 4. Climate Change 5: Evolution 1. Evolution Evidence 2. Natural Selection 3. Classification 4. Cladistics 6: Human Physiology 1. Digestion 2. The Blood System 3. Disease Defences 4. Gas Exchange 5. Homeostasis Higher Level 7: Nucleic Acids 1. DNA Structure 2. Transcription 3. Translation 8: Metabolism 1.
Metabolism 2. Cell Respiration 3. Photosynthesis 9: Plant Biology 1.
0コメント