In the microarray

In the microarray data we identified several putative pep tide hormone transcript highly expressed in the root mer istem. The probe set, expression confirmed by qRT PCR has strong protein sequence similarity to the Arabidopsis gene DEVIL 19, a member of the DVL gene family. Some DVL peptides have been in shown to inhibit cell proliferation during Inhibitors,Modulators,Libraries leaf development, their receptor is unknown. We also find transcripts homologous to Rapid Alkalization Factors expressed highly in the meristem have been shown to act as peptide hormones in tobacco and Arabidopsis. These peptides may have a role in M. truncatula meristem maintenance. Transcription factors Of the 2,957 probe sets on the genome array have sequence homology to described plant Inhibitors,Modulators,Libraries TFs, 37 predicted TFs were up regulated in meristem and 18 TFs were up regulated at least 2 fold in non meristematic cells.

Of the 64 predicted TF families in the DATF database, only 21 were differentially expressed in meris tem and non meristematic root. Of these, nine Inhibitors,Modulators,Libraries families were significantly over represented within the up regulated probe sets, no TF families were over represented in the non meristem. The families up regulated in the meristem are the basic helix loop helix, basic leucine zipper, growth regulating factor and the GRF interacting factors, APETALA2 and ethylene responsive element binding pro teins, auxin responsive protein indoleace tic acid induced protein, GATA factors, auxin response factors and plant AT rich sequence and zinc binding proteins. With the exception of bHLH, bZIP and C2C2 GATA domain con taining TFs, the significantly up regulated TF gene families are plant specific.

We confirmed the expression of several TFs that significantly accumulate in the meristem using qRT PCR. FiveAP2 EREPB domain containing TFs expressed in the meristematic root, including BABY BOOM1 and two with described Arabidopsis Inhibitors,Modulators,Libraries orthologs. Inhibitors,Modulators,Libraries Tandem AP2 domain transcription factors are strongly associated with plant development, and PLETHORA and BABY BOOM with root development where they have recently been shown to be dose dependent regulators of root stem cell identity and maintenance. The accumulation of these tran scripts in the Medicago root meristem and absence of expression in the differentiated root is consistent with these findings. Auxin is key regulator of plant gene expression and the AUX IAA and ARF TFs are important regulators of auxin response.

AUX IAA TFs repress the expression of auxin activated genes until they are degraded by the SCFTIR1 E3 ubiquitin ligase complex in the presence of IAA. ARFs can activate or repress transcription in the presence of auxin by binding to auxin response selleck kinase inhibitor elements. Two AUX IAA transcripts are highly expressed in the meristem, Mtr. 22904. 1. S1. at and Mtr. 16803. 1. S1.

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