Interplay between the shoot apical meristem and lateral organs
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aBIOTECH
REVIEW
Interplay between the shoot apical meristem and lateral organs Chunmei Guan1 , Yuling Jiao1,2& 1
2
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China University of Chinese Academy of Sciences, Beijing 100049, China
Received: 24 March 2020 / Accepted: 9 May 2020
Abstract
Tissues and organs within a living organism are coordinated, but the underlying mechanisms are not well understood. The shoot apical meristem (SAM) continually produces lateral organs, such as leaves, from its peripheral zone. Because of their close proximity, SAM and lateral organs interact during plant development. Existing lateral organs influence the positions of newly formed organs to determine the phyllotaxis. The SAM not only produces lateral organs, but also influences their morphogenesis. In particular, the SAM promotes leaf polarity determination and leaf blade formation. Furthermore, lateral organs help the SAM to maintain homeostasis by restricting stem cell activity. Recent advances have started to elucidate how SAM and lateral organs patterning and growth are coordinated in the shoot apex. In this review, we discuss recent findings on the interaction between SAM and lateral organs during plant development. In particular, polar auxin transport appears to be a commonly used coordination mechanism.
Keywords Shoot apical meristem, Lateral organ, Morphogenesis, Sussex signal, Auxin
INTRODUCTION The majority of the above-ground shoot comes from the shoot apical meristem (SAM). Established during embryogenesis, the SAM contains a mass of stem cells in the center. Stem cells in the SAM divide to maintain new stem cells and to provide cells that make new primordia on the periphery (Fletcher 2018; Shi and Vernoux 2019). During vegetative growth, leaves are the most common lateral organs produced by the SAM. Whereas seed plant leaves are determinate, which contrasts to the indeterminate SAM, axillary meristems (AMs) form in the leaf axil to enable branching (Wang and Jiao 2018). AMs share the same structure and developmental potential as the SAM. AMs produce their own & Correspondence: [email protected] (Y. Jiao)
lateral organs and make the shoot a ramifying system where the growth of new shoots can be initiated. After floral transition, the SAM generates floral primordia instead of leaf primordia in plants with a simple raceme, an indeterminate inflorescence, such as in Arabidopsis. A floral primordia contains a floral meristem that produces a limited number of floral organs, including sepals, petals, stamens and carpels, to make a flower. Although a flower is a modified, shortened, compacted branch, the floral primordium behaves in many ways similar to the leaf primordium. Thus, floral primordia are often treated as lateral organs (Long and Barton 2000). In this review, we focus on the interplay of the SAM and lateral organs. We refer the readers to
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