Establishment of an efficient alfalfa regeneration system via organogenesis and the co-expression of Arabidopsis SOS genes improves salt tolerance in transgenic alfalfa (Medicago sativa L.)

The Salt Overly Sensitive (SOS) signal transduction pathway is pivotal in Na+ efflux and facilitates ion transport and homeostasis for improved salt tolerance in plants. Ten alfalfa varieties were used as experimental materials, and two alfalfa regeneration systems were established and optimized. Cotyledons and hypocotyls were initially used as explants to induce embryogenic callus via the indirect production of somatic embryos in order to establish a callus acceptor system. Cotyledonary nodes were used as explants to induce adventitious bud formation via direct organogenesis, thereby establishing an in vitro regeneration system that could be used for the genetic transformation. Agrobacterium-mediated transformation of the cotyledonary nodes of the alfalfa cv. â Golden Empress bâ was used to generate 25 independent sources of transformed plants exhibiting herbicide tolerance. Four of the positive transgenic plants were randomly selected for southern blot analysis, and three hybridization signals with one or two copies were detected. Reverse transcription PCR showed that the Bialaphos resistance (Bar) and SOS1 genes were expressed in the transgenic plants and that multiple exogenous salt-tolerant genes were integrated into the transgenic plant genome and expressed at the transcriptional level. The overexpression of Arabidopsis SOS genes in alfalfa conferred a high degree of salinity tolerance, enhanced plant growth, a lowered accumulation of Na+, increased accumulation of K+ in the leaves, and altered physiological and biochemical parameters in response to salt stress.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author