truncatula supports motion that the prolonged 17-AAG mechanism auxin signalling may have adverse effect on embryo formation. Proliferation of undifferentiated callus tissue, greening, and the formation of shoot structures are all cytokinin dependent processes. We have identified a response regu lator that is up regulated in the embryogenic cultures. This probe set was also up reg ulated in the developing seeds at 10 days after pollination when compared to leaf samples, indicating some similar ities between somatic and zygotic embryogenesis. MtRR1 is an ortholog of Arabidopsis ARR10 that belongs to B type response regulators. It was reported that this gene is induced early in M. truncatula roots during the symbiotic interaction with Sinorhizobium meliloti. There are other probe sets for the genes involved in cytokinin biosynthesis and sig nalling.

However, these were not changed between the two cultures. For instance, there are two probe sets for ade nylate isopentenyltransferases in the array and both probe sets did not expressed in both cultures. In con Inhibitors,Modulators,Libraries trast, Cytokinin Response 1, some differences between the embryogenic line 2HA and the non embryogenic Inhibitors,Modulators,Libraries line Jemalong in respond to cytoki nin and MtRR1 may be an important regulator in the acquisition of regeneration capacity in M. truncatula. Conclusion We have described differences in transcriptomes between the M. truncatula super embryogenic line 2HA and its non embryogenic progenitor Jemalong. Notably they include significant variations in carbon and flavonoid metabolism, phytohormone biosynthesis and signalling, cell to cell communication and gene regulation.

This data will facilitate the mapping of regulatory and metabolic networks involved in the acquisition of regeneration capacity of the embryogenic lines such as 2HA, and may lead to a better understanding of totipotency in M. trunca tula and other legume species. Methods Inhibitors,Modulators,Libraries Plant Inhibitors,Modulators,Libraries materials, growth and tissue culture M. truncatula cv Jemalong seed line 2HA and its progeni tor Jemalong was used for the plant growth explant tissue culture as described. Seeds of M. truncatula cv Jemalong were obtained from Professor Ray Rose. Plants were grown under controlled growth cabinet conditions with 12 hr Inhibitors,Modulators,Libraries photoperiod at 150mol m 2 s 1 with a day temperature of 23 C and a night temperature of 19 C and a relative humidity of 80%.

The basal medium used for the explant leaf culture was P4, which is based on Gamborgs B5 medium as described. In the usual culture procedure, leaf explants were plated onto P4 medium containing 10M NAA and 4 M BAP. Cultures were incubated in the dark at 28 C. DNA microarray analysis The Affymetrix Medicago GeneChip contained 61,200 probe sets 32,167 M. truncatula EST based and chloroplast Oligomycin A gene based probe sets. 18,733 M. truncatula IMGAG and phase 2 3 BAC prediction based probe sets. 1,896 M. sativa EST mRNA based probe sets. 8,305 Sinorhizobium meliloti gene prediction based probe sets.