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Medicago truncatula is a model legume, whose genome is currently being sequenced. Somatic embryogenesis (SE) is a genotype-dependent character and not yet fully understood. In this study, a proteomic approach was used to compare the induction and expression phases of SE of both the highly embryogenic line M9-10a of M. truncatula cv. Jemalong and its non-embryogenic predecessor line, M9. The statistical analysis between the lines revealed 136 proteins with significant differential expression (P < 0.05). Of these, 5 had a presence/absence pattern in M9 vs M9-10a and 22 showed an at least twofold difference in terms of spot volume, were considered of particular relevance to the SE process and therefore chosen for identification. Spots were excised in gel digested with trypsin and proteins were identified using matrix-assisted laser desorption ionization-time of flight/time of flight. Identified proteins indicated a higher adaptability of the embryogenic line toward the stress imposed by the inducing culture conditions. Also, some proteins were shown to have a dual pattern of expression: peroxidase, pyrophosphatase and aspartate aminotransferase. These proteins showed higher expression during the induction phases of the M9 line, whereas in the embryogenic line had higher expression at stages coinciding with embryo formation.

In this article, we present the response of Medicago truncatula Gaert. cv. Jemalong plants expressing constitutively the Dsp22 gene from Craterostigma plantagineum to water stress and rehydration. The Dsp22 gene encodes an ELIP-like protein thought to protect the chloroplast against photooxidative damage during the dehydration and rehydration. The Dsp22 transgenic homozygous M. truncatula plants showed higher amount of chlorophyll (Chl), lower Chl a/Chl b ratio and higher actual efficiency of energy conversion in photosystem 2 (Φ PSII ) after rehydration when compared to the wild type. The combined data from the Chl a fluorescence analysis, pigment quantification, and biomass accumulation showed that transgenic M. truncatula plants are able to recover from water deprivation better than wild type plants.

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Molecular pharming is a cost-effective, scalable, and safe system to produce high-quality and biologically active recombinant therapeutic proteins. Thus, plants are emerging alternative platform for the production of pharmaceutically relevant proteins such as vaccines, antibodies, antibody derivatives, and some serumderived proteins. Additionally, plants have also been used to produce bioactive and immunogenic peptides. The efficacy, selectivity, specificity, and low toxicity make them particularly well-suited therapeutic agents for various indications, for instance, cardiovascular and infectious diseases, immunological disorders, and cancer. In the broad range of known bioactive peptides, angiotensin I-converting enzyme inhibitory (ACEI) peptides derived from food proteins have attracted particular attention for their ability to prevent hypertension. So far, several ACEI peptides have been identified in food proteins, mainly in milk, eggs, and plants. The industrial production of ACEI peptides is based on enzymatic proteolysis of whole food proteins, which leads to the release of small bioactive peptides with ACE-inhibitory activity. The problems associated to such procedures, namely, cost and loss of functional properties, have demonstrated the need to develop more straightforward methods to produce ACEI peptides. One viable hypothesis, discussed in this chapter, is to genetically engineer crop plants to produce and deliver antihypertensive peptides.

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We developed an alternative methodology for in vitro selection of transgenic Medicago truncatula cv. Jemalong plants using a bifunctional construct in which the coding sequences for the green fluorescent protein (GFP) and the b-glucuronidase protein (GUS) are fused. An Agrobacterium-mediated transformation protocol was used followed by regeneration via somatic embryogenesis in the dark, to avoid the synthesis and the consequent autofluorescence of chlorophyll. This method is a clear advantage over antibiotic and herbicide selection in which survival of non-transformed tissue is commonly reported, with the reassurance that all the somatic embryos selected as GFP positive are transformed. This was subsequently corroborated by the detection of GUS activity in leaves, stems and roots of the regenerated plants. Without antibiotic selection, and performing the embryo induction in the dark, it was possible to attest the advantage of using GFP as an in vivo detectable reporter for early embryo selection. The fusion with the GUS coding sequence provided additional evidence for the transformation of the previously selected embryos.