Transcriptome analyses of ragged seedling2 shoot apical meristem (SAM) vs non-mutant SAM
Ontology highlight
ABSTRACT:
ORGANISM(S): Zea mays
SUBMITTER: Michael Scanlon
PROVIDER: E-GEOD-11325 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Scaffold proteins such as CNK1 are hubs for coordinating signalling pathways. Here, we demonstrate that CNK1 is a crucial transducer of growth factor-stimulated and oncogenic signalling. Activation of CNK1 depends on its dimerization executed by the N-terminal sterile motif alpha (SAM) domain. Accordingly, a CNK1 mutant lacking the SAM domain prevents CNK1-driven cell proliferation and matrix metalloproteinase 14 promoter activation. We identified phosphorylation of Ser22 by AKT as trigger for CNK1 dimerisation. Consistently, the mutant CNK1S22D mimicking constitutive phosphorylation stimulates CNK1 signalling, whereas the phosphoylation-dead mutant CNK1S22A does not. Searching the COSMIC database revealed Ser22 as target for oncogenic activation of CNK1. The mutant CNK1S22D and the oncogenic mutant CNK1S22F form clusters in serum-starved cells comparable to clusters of CNK1 in growth factor stimulated cells. Light-activatable CNK1, optoCNK1, based on the light-induced oligomerisation of cryptochrome 2 confirms that dimerization is the trigger for CNK1 activation. CNK1 dimers induced by activating Ser22 mutants or by light enhance cell invasion and ADP ribosylation factors 1 signalling associated with tumour formation. Positive and negative feedback mechanisms regulates CNK1 dimerisation and in this way its activity. Oncogenic mutants of CNK1 support the positive feedback while escape from negative feedback regulation.
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Project description:All above ground organs of higher plants are ultimately derived from specialized organogenic structures called shoot apical meristems (SAMs). It is comprised of pluripotent stem cells, which divide to regenerate themselves as well as to provide cells to form other organs such as leaves and stems. To study global gene expression in maize SAM and very young primordia (P0 and P1), RNA was extracted from both SAMs (SAMs per se plus P0 and P1) and above-ground portions of seedlings collected from 14-day old B73 seedlings. These RNA samples were labeled and hybridized with cDNA microarrays that have 14,400 informative spots from maize. Statistical analyses showed that approximately 6.3% and 6.5% of the tested genes were significantly (p <0.0001) up- and down-regulated, respectively. Several control genes, whose expressions were confirmed in the maize SAM in the previous studies, were also up-regulated (p <0.01). The significantly up-regulated genes involved many novel transcription factor genes and regulatory genes as well as some kinds of enzymes, suggesting these genes play important roles in meristem maintenance and the early stage of leaf development in maize. Interestingly, several retrotransposon-related genes were greatly up-regulated in the SAM. This finding raised the possibility that retrotransposons are involved in regulatory mechanisms of maize SAM. An experimental aim is to identify genes preferentially expressed in maize SAM by comparing the transcript abundant between SAMs and seedlings using cDNA microarrays that have 14,400 informative spots from maize.
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