Spartina alterniflora Loisel., a halophyte grass model to dissect salt stress tolerance

Salinity is one of the most serious abiotic stresses affecting crop productivity worldwide. Improving tolerance to salinity in field crops is globally important because a majority of the world population relies on salt-sensitive crops such as rice, corn, and wheat for their daily calories. Although there is no salt stress sensor yet identified, different signaling components and tolerance mechanisms have been substantiated to a great extent in a glycophyte like Arabidopsis, and more recently in a few halophytes. With the rapid advances in genetics, genomics, and biochemical and transformation tools, it is now possible to explore the genetic and molecular basis of the unusually high level of salt tolerance in halophilic plants. We will focus on a halophyte grass, Spartina alterniflora, commonly known as smooth cordgrass, which possesses all known mechanisms of salt tolerance and subsequent exploitation of its genome information for crop improvement. A number of candidate genes encoding transcription factors, ion transport, osmoprotectants, antioxidants, detoxifying enzymes, etc. have been identified. Although recent efforts to develop salt tolerant cultivars that could retain the halophytic traits through transgenesis show some promise, further exploration is needed to test the contribution of single or multiple salt stress-related genes or regulatory factors from halophilic plants, including S. alterniflora, for possible utilization in crop improvement.