Animals develop all their organs entirely during embryogenesis. On the contrary, only few organs are established during plant embryogenesis. The development of all the plant organs depends on post-embryonic activity of the shoot apical meristem (SAM) and t he root meristem, which are established during embryogenesis.
Plant development and growth depends on the ability of the SAM to renew itself and at the same time differentiate into various organs. These processes are strictly regulated and coordinated by meristematic genes, by local hormonal balance and by abiotic stimuli.
In plants, the class 1 KNOX (KNOTTED1-like) family plays an important role in the formation and maintenance of the SAM. KNOX gene expression is first detected as the meristem is established in the embryo and disappears from cells that will give rise to leaf primordia. Over-expression of KNOX genes strongly affects cell fate.
Altered cell differentiation produces dramatic changes of the whole plant architecture and leaf morphology. Mutations of some class 1 genes result in seedlings that germinate, but fail to develop any further. KNOX proteins interact with other homeodomain proteins (BELL). In animals the KNOX/BELL complex contains at least 3 subunits. In plants, KNOX and BELL proteins interact and bind the same nucleotide sequence.
These findings support the hypothesis that a third interactor must provide binding-site specificity for the differential regulation of KNOX target genes. We propose a multidisciplinary project aimed at identifying KNOX primary target genes and interactors of the KNOX/BELL complex.
An innovative application of Chromatin ImmunoPrecipitation (ChIP) modified for gene and protein discovery will be developed. This new approach will allow for the identification of KNOX target genes and new members of the KNOX/BELL complex.
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