Disease relevance of STM

• Using in situ hybridization, we analyzed the expression of KNAT1 and another kn1-like homeobox gene, SHOOT MERISTEMLESS, in cauliflower mosaic virus 35S::KNAT1 transformants [1].
• The SHOOT MERISTEMLESS (STM) promoter was used to drive expression in the shoot apical meristem (SAM) and a subset of cells at the base of the hypocotyl of 1x,2x, and 3x soluble green fluorescent proteins (sGFPs), and the P30 movement protein of Tobacco mosaic virus (TMV) translationally fused to 1x and 2x sGFP [2].
• Antisense inhibition of SHL expression gives rise to dwarfism and delayed development [3].

High impact information on STM

• A member of the KNOTTED class of homeodomain proteins encoded by the STM gene of Arabidopsis [4].
• Here we present evidence that the Arabidopsis SHOOT-MERISTEMLESS (STM) gene, required for shoot apical meristem formation during embryogenesis, encodes a class I KNOTTED-like protein [4].
• Monitoring the patterns of LAS and SHOOT MERISTEMLESS transcript accumulation allowed us to identify early steps in the development of leaf axil identity, which seem to be a prerequisite for axillary meristem initiation [5].
• During embryogenesis, KNAT6 is expressed later than STM and CUC [6].
• To isolate insertions in specific genes, we developed three-dimensional pooling and polymerase chain reaction strategies that we then validated by identifying mutants for the regulator genes APETALA1 and SHOOT MERISTEMLESS [7].

Biological context of STM

• Conversely, STM suppresses differentiation independently of WUS and is required and sufficient to promote cell division [8].
• The as1 and as2 mutations genetically enhance 35S::CUC1 phenotypes even in the absence of STM function [9].
• Ectopic STM and WUS functions interacted non-additively and activated a subset of meristem functions, including cell division, CLAVATA1 expression and organogenesis, but not correct phyllotaxy or meristem self-maintenance [10].
• Increased steady state mRNA levels of the STM and KNAT1 homeobox genes in cytokinin overproducing Arabidopsis thaliana indicate a role for cytokinins in the shoot apical meristem [11].
• The steady state transcript levels of the histidine kinase CKI1 gene and the KNAT1 and STM homeobox genes were increased in tsd mutants, while mRNA levels of cell cycle genes were not altered [12].

Anatomical context of STM

• 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 [13].
• The results showed that the C-terminal 10-amino acid region containing an SKL motif-like tripeptide (SHL) was not required for the import into peroxisomes [14].

Associations of STM with chemical compounds

• Application of exogenous cytokinin or expression of a cytokinin biosynthesis gene through the STM promoter partially rescued the stm mutant [15].
• Despite the severity of the induced ipt phenotypes, transcripts for the KNOX homoeodomain transcription factors BREVIPEDICELLUS and SHOOTMERISTEMLESS were not significantly increased within 48 h of dexamethasone application to seedlings [16].

Other interactions of STM

• We demonstrate that KNAT6 contributes redundantly with STM to the maintenance of the shoot apical meristem (SAM) and organ separation [6].
• In this report, we examined the role of PNY, PNF and STM during development [17].
• We show that stem cell specification by WUS does not require STM activity [8].
• Genes required for STM expression, such as CUP-SHAPED COTYLEDON 1 and 2 (CUC1 and 2) were upregulated prior to shoot commitment [18].
• Therefore, while STM appears to function in keeping central meristem cells undifferentiated, WUS and ZLL seem to be subsequently required for proper function of these cells [19].

Analytical, diagnostic and therapeutic context of STM

• While Eschscholzia californica STM (EcSTM) is again upregulated during acropetal pinna formation, in situ hybridization could not detect Chelidonium majus STM (CmSTM) transcripts at any stage of basipetal leaf development, indicating divergent evolution of STM gene function in leaves within Papaveraceae [20].
• Zygotic embryos of three Arabidopsis thaliana (L.) Heynh. mutants lacking an embryonic shoot apical meristem (SAM), shoot meristemless (stm), wuschel (wus) and zwille/pinhead (zll/pnh) were used as explants to establish embryogenic cell cultures [21].
• Scanning electron microscopy, histology and RNA in situ analysis with SHOOTMERISTEMLESS ( STM), a marker for meristematic tissues, show that a mound of cells form and STM mRNA accumulates in barren leaf axils, indicating that axillary meristems initiate but arrest in their development prior to organizing a meristem proper [22].

References