15
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      HAM proteins promote organ indeterminacy : But how?

      review-article
      Plant Signaling & Behavior
      Landes Bioscience
      AINTEGUMENTA, CLAVATA3, corpus, GRAS, HAM, indeterminacy, meristem, stem cell, tunica

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          HAIRY MERISTEM (HAM) proteins, members of the GRAS family of transcriptional regulators, are essential for maintenance of indeterminate growth in flowering plant shoots, loss-of-function ham mutants exhibiting a strikingly novel phenotype of shoot meristem arrest and differentiation. Specific cellular/molecular functions of HAM proteins underlying meristem maintenance are unknown. In this review, I highlight findings from recent analyses of Arabidopsis ham ( Atham) loss-of-function phenotypes, including that HAM function limits the generation of clonally-derived meristem layers and that HAM function regulates CLAVATA3 expression. I consider how this new information both refines our understanding of the role of HAM proteins in regulating meristem structure and function, and may also suggest possible downstream HAM protein transcriptional targets. Finally, I note the significant phenotypic overlap between Atham phenotypes, and aintegumenta/ anintegumenta-like6 double mutant phenotypes, suggesting meristem regulatory functions common to, and possible genetic interactions between, HAM and AINTEGUMENTA.

          Related collections

          Most cited references43

          • Record: found
          • Abstract: found
          • Article: not found

          The stem cell population of Arabidopsis shoot meristems in maintained by a regulatory loop between the CLAVATA and WUSCHEL genes.

          The higher-plant shoot meristem is a dynamic structure whose maintenance depends on the coordination of two antagonistic processes, organ initiation and self-renewal of the stem cell population. In Arabidopsis shoot and floral meristems, the WUSCHEL (WUS) gene is required for stem cell identity, whereas the CLAVATA1, 2, and 3 (CLV) genes promote organ initiation. Our analysis of the interactions between these key regulators indicates that (1) the CLV genes repress WUS at the transcript level and that (2) WUS expression is sufficient to induce meristem cell identity and the expression of the stem cell marker CLV3. Our data suggest that the shoot meristem has properties of a self-regulatory system in which WUS/CLV interactions establish a feedback loop between the stem cells and the underlying organizing center.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Direct control of shoot meristem activity by a cytokinin-activating enzyme.

            The growth of plants depends on continuous function of the meristems. Shoot meristems are responsible for all the post-embryonic aerial organs, such as leaves, stems and flowers. It has been assumed that the phytohormone cytokinin has a positive role in shoot meristem function. A severe reduction in the size of meristems in a mutant that is defective in all of its cytokinin receptors has provided compelling evidence that cytokinin is required for meristem activity. Here, we report a novel regulation of meristem activity, which is executed by the meristem-specific activation of cytokinins. The LONELY GUY (LOG) gene of rice is required to maintain meristem activity and its loss of function causes premature termination of the shoot meristem. LOG encodes a novel cytokinin-activating enzyme that works in the final step of bioactive cytokinin synthesis. Revising the long-held idea of multistep reactions, LOG directly converts inactive cytokinin nucleotides to the free-base forms, which are biologically active, by its cytokinin-specific phosphoribohydrolase activity. LOG messenger RNA is specifically localized in shoot meristem tips, indicating the activation of cytokinins in a specific developmental domain. We propose the fine-tuning of concentrations and the spatial distribution of bioactive cytokinins by a cytokinin-activating enzyme as a mechanism that regulates meristem activity.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              The no apical meristem gene of Petunia is required for pattern formation in embryos and flowers and is expressed at meristem and primordia boundaries.

              Petunia embryos carrying the no apical meristem (nam) mutation fail to develop a shoot apical meristem. Occasional shoots on nam- seedlings bear flowers that develop ten instead of five primordia in the second whorl. Double mutants with the homeotic gene green petals show that nam acts independently of organ identify in whorl 2 and now also affects primordium number in whorl 3. The nam gene was isolated by transposon tagging. The encoded protein shares a conserved N-terminal domain with several other proteins of unknown function and thus represents a novel class of proteins. Strikingly, nam mRNA accumulates in cells at the boundaries of meristems and primordia. These data indicate a role for nam in determining positions of meristems and primordia.
                Bookmark

                Author and article information

                Journal
                Plant Signal Behav
                Plant Signal Behav
                PSB
                Plant Signaling & Behavior
                Landes Bioscience
                1559-2316
                1559-2324
                01 February 2012
                01 February 2012
                : 7
                : 2
                : 227-234
                Affiliations
                Biology Department; The College of William and Mary; Williamsburg, VA USA
                Author notes
                Correspndence to: Eric M. Engstrom; Email: emengs@ 123456wm.edu
                Article
                2011PSB0515 18958
                10.4161/psb.18958
                3405703
                22353859
                b9a1de46-2e60-4e02-8d30-cecb1dfd07ed
                Copyright © 2012 Landes Bioscience

                This is an open-access article licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. The article may be redistributed, reproduced, and reused for non-commercial purposes, provided the original source is properly cited.

                History
                Categories
                Review

                Plant science & Botany
                ham,tunica,aintegumenta,stem cell,clavata3,gras,meristem,indeterminacy,corpus
                Plant science & Botany
                ham, tunica, aintegumenta, stem cell, clavata3, gras, meristem, indeterminacy, corpus

                Comments

                Comment on this article