title: Developmental events and shoot apical meristem gene expression patterns during shoot development in Arabidopsis thaliana.
abstract: Critical developmental and gene expression profiles were charted during the formation of shoots from root explants in Arabidopsis tissue culture. Shoot organogenesis is a two-step process involving pre-incubation on an auxin-rich callus induction medium (CIM) during which time root explants acquire competence to form shoots during subsequent incubation on a cytokinin-rich shoot induction medium (SIM). At a histological level, the organization of shoot apical meristems (SAMs) appears to occur during incubation on SIM about the time of shoot commitment, i.e. the transition from hormone-dependent to hormone-independent shoot development. Genes involved in SAM formation, such as SHOOTMERISTEMLESS (STM) and CLAVATA1 (CLV1), were upregulated at about the time of shoot commitment, while WUSCHEL (WUS) was upregulated somewhat earlier. Genes required for STM expression, such as CUP-SHAPED COTYLEDON 1 and 2 (CUC1 and 2) were upregulated prior to shoot commitment. Gene expression patterns were determined for two GFP enhancer trap lines with tissue-specific expression in the SAM, including one line reporting on CUC1 expression. CUC1 was generally expressed in callus tissue during early incubation on SIM, but later CUC1 was expressed more locally in presumptive sites of shoot formation. In contrast, the expression pattern of the enhancer trap lines during zygotic embryogenesis was more localized to the presumptive SAM even in early stages of embryogenesis.
authors.affiliation: Boyce Thompson Institute and Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Cary
authors.forename: Ping
authors.initials: P
authors.lastname: Che
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Howell
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D046508:Culture Techniques; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000235:genetics* / Q000254:growth & development; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development; D018520:Plant Shoots / Q000235:genetics* / Q000254:growth & development; D017346:Protein Serine-Threonine Kinases; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C426007:CUC1 protein, Arabidopsis; C107294:CUC2 protein, Arabidopsis; D018398:Homeodomain Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; C097496:STM protein, Arabidopsis; C116421:WUSCHEL protein, Arabidopsis; D049452:Green Fluorescent Proteins; D020794:Receptor Protein-Tyrosine Kinases; C118166:CLV1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases