Interplay between the shoot apical meristem and lateral organs

Regularity and periodicity in the arrangements of organs in all groups of land plants raise questions about the mechanisms underlying phyllotactic pattern formation. The initiation of the lateral organs (leaves, flowers, etc.), and thus, their spatio-temporal positioning, occurs in the shoot apical meristem (SAM) and is related to the structure and organogenic activity of the meristem. In this review, we present some aspects of the diversity and stability of phyllotactic patterns in the major lineages of land plants, from bryophytes to angiosperms, in which SAM structures differ significantly. In addition, we discuss some of the possible mechanisms involved in the formation of the recurring arrangement of the lateral organs.

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Expression of maize KNOTTED1 related homeobox genes in the shoot apical meristem predicts patterns of morphogenesis in the vegetative shoot

Development ◽

10.1242/dev.120.2.405 ◽

1994 ◽

Vol 120 (2) ◽

pp. 405-413 ◽

Cited By ~ 32

Author(s):

D. Jackson ◽

B. Veit ◽

S. Hake

Keyword(s):

Shoot Apical Meristem ◽

Leaf Development ◽

Apical Meristem ◽

Expression Patterns ◽

Homeobox Genes ◽

Homeobox Gene ◽

Vegetative Shoot ◽

Lateral Organs ◽

Floral Meristems ◽

Shoot Meristems

In this paper we describe the expression patterns of a family of homeobox genes in maize and their relationship to organogenic domains in the vegetative shoot apical meristem. These genes are related by sequence to KNOTTED1, a gene characterized by dominant neomorphic mutations which perturb specific aspects of maize leaf development. Four members of this gene family are expressed in shoot meristems and the developing stem, but not in determinate lateral organs such as leaves or floral organs. The genes show distinct expression patterns in the vegetative shoot apical meristem that together predict the site of leaf initiation and the basal limit of the vegetative ‘phytomer’ or segmentation unit of the shoot. These genes are also expressed in the inflorescence and floral meristems, where their patterns of expression are more similar, and they are not expressed in root apical meristems. These findings are discussed in relation to other studies of shoot apical meristem organization as well as possible commonality of homeobox gene function in the animal and plant kingdoms.

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ASYMMETRIC LEAVES1 reveals knox gene redundancy in Arabidopsis

Development ◽

10.1242/dev.129.8.1957 ◽

2002 ◽

Vol 129 (8) ◽

pp. 1957-1965 ◽

Cited By ~ 10

Author(s):

Mary E. Byrne ◽

Joseph Simorowski ◽

Robert A. Martienssen

Keyword(s):

Shoot Apical Meristem ◽

Apical Meristem ◽

Cell Function ◽

The Novel ◽

Knox Gene ◽

Knox Genes ◽

Lateral Organs ◽

Gene Redundancy ◽

Lateral Organ ◽

Meristem Maintenance

The shoot apical meristem comprises undifferentiated stem cells and their derivatives, which include founder cells for lateral organs such as leaves. Meristem maintenance and lateral organ specification are regulated in part by negative interactions between the myb domain transcription factor ASYMMETRIC LEAVES1, which is expressed in lateral organ primordia, and homeobox transcription factors which are expressed in the shoot apical meristem (knox genes). The knox gene SHOOT MERISTEMLESS (STM) negatively regulates ASYMMETRIC LEAVES1 (AS1) which, in turn, negatively regulates other knox genes including KNAT1 and KNAT2, and positively regulates the novel gene LATERAL ORGAN BOUNDARIES (LOB). Genetic interactions with a second gene, ASYMMETRIC LEAVES2 (AS2), indicate it acts at the same position in this hierarchy as AS1. We have used a second-site suppressor screen to isolate mutations in KNAT1 and we show that KNAT1 is partially redundant with STM in regulating stem cell function. Mutations in KNAT2 show no such interaction. We discuss the regulation and evolution of redundancy among knox genes.

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An integrated analysis of cell-type specific gene expression reveals genes regulated by REVOLUTA and KANADI1 in the Arabidopsis shoot apical meristem

PLoS Genetics ◽

10.1371/journal.pgen.1008661 ◽

2020 ◽

Vol 16 (4) ◽

pp. e1008661 ◽

Cited By ~ 2

Author(s):

Hasthi Ram ◽

Sudeep Sahadevan ◽

Nittaya Gale ◽

Monica Pia Caggiano ◽

Xiulian Yu ◽

...

Keyword(s):

Gene Expression ◽

Shoot Apical Meristem ◽

Apical Meristem ◽

Integrated Analysis ◽

Specific Gene ◽

Cell Type ◽

Specific Gene Expression ◽

Cell Type Specific

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Sample preparation for laser-microdissection of soybean shoot apical meristem

International Journal of Plant Biology ◽

10.4081/pb.2012.e3 ◽

2012 ◽

Vol 3 (1) ◽

pp. 3 ◽

Cited By ~ 1

Author(s):

Chui E. Wong ◽

Mohan B. Singh ◽

Prem L. Bhalla

Keyword(s):

Sample Preparation ◽

Shoot Apical Meristem ◽

Apical Meristem ◽

Laser Microdissection ◽

Specific Cell ◽

Legume Crop ◽

Continuous Formation ◽

Molecular Events ◽

Depth Analysis ◽

Specialized Equipment

The shoot apical meristem houses stem cells responsible for the continuous formation of aerial plant organs including leaves and stems throughout the life of plants. Laser-microdissection in combination with high-throughput technology such as next generation sequencing permits an in-depth analysis of molecular events associated with specific cell type of interest. Sample preparation is the most critical step in ensuring good quality RNA to be extracted from samples following laser-microdissection. Here, we optimized the sample preparation for a major legume crop, soybean. We used Farmer’s solution as a fixative and paraffin as the embedding medium for soybean shoot apical meristem tissue without the use of any specialized equipment. Shorter time for tissue fixation (two days) was found to be critical for the preservation of RNA in soybean shoot apical meristem. We further demonstrated the utility of this method for different tissues derived from soybean and rice. The method outlined here shall facilitate studies on crop plants involving laser-microdissection.

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