The relationship between nearly anthocyanin deposition and polar auxin transport in the root has not been tested. Hormones and cell to cell communication In our analysis of plant gene families we could identify probe sets that indicated that there are significant differ ences in cell to cell communication and response to hor mones in the meristem and non meristematic root. Auxin transport in the RAM is by a system of auxin efflux carrier Inhibitors,Modulators,Libraries proteins from the PIN family, has been well described in M. truncatula. PIN proteins are localised in an asym metric distribution on either the basal or apical side of cells where they control PAT, their expression and reorganisation is also essential for creating localised auxin gradients which are required for many aspects of plant development. In the M.

truncatula root, MtPIN2 is expressed in the root, our data also showed the expression of this gene, specifically up regulated in the root meristem, consistent with the reported locali sation of the AtPIN2 Inhibitors,Modulators,Libraries protein, where its localisation directs auxin flow from the root tip into the elongation zone and is crucial in mediating the gravitropic Inhibitors,Modulators,Libraries response. Our array data, confirmed by qRT PCR, also shows that MtPIN9 is preferentially expressed in the non meristematic root. Multidrug resistance P glyco protein type ABC transporters also function as auxin efflux carriers, Inhibitors,Modulators,Libraries our data shows the over expression of three homologous transcripts in the non meristem with strong C terminal protein sequence simi larity with Arabidopsis Multidrug Resistance Like1 and MDR4, two transporters recently shown to mediate acropetal and basipetal auxin transport proximal to the meristem respectively.

Cytokinin also contributes to the establishment and maintenance of the RAM, and recently it has been shown that cytokinin controls the rate of meristematic cell differ Inhibitors,Modulators,Libraries entiation determining the size of the RAM through a two component receptor histidine kinase transcription factor signalling pathway. In the RAM cytokinin is detected by, which leads to the expression of transcription factors. In our root meristem section we were able to detect the accumulation of a probe set orthol ogous to ARABIDOPSIS HISTIDINE KINASE 5. AHK5 has been shown to be expressed in the elongating root where it acts as a negative regulator in the signaling pathway in which ethylene and abscisic acid inhibit root elongation through ethylene receptor ETR1. Receptor like kinases have been implicated in numerous developmental research only signalling pathways in plant development. We see significant differential expression of three RLKs in the meristem Mtr. 1137. 1. S1 s at is an ortholog of CLAVATA1, the leucine rich RLK responsible for specification of the SAM through interaction with the CLAVATA3 peptide.