AbstractsBiology & Animal Science

Spartina alterniflora is a dominant salt marsh cordgrass along the U.S. Atlantic and Gulf coasts, and the species is widely used for wetland restoration in Louisiana. S. alterniflora seeds are shed dormant from the mother plant. However, long-term preservation of S. alterniflora seeds is challenging because the seeds are recalcitrant, losing viability when dried below 45% water content. In this dissertation, I investigated the following three aspects of S. alterniflora: recalcitrance, dormancy release by cold stratification and the effect of drying temperature on the critical water content. Comparative proteomics between S. alterniflora and orthodox, desiccation tolerant Spartina pectinata seeds identified 83 heat-stable (soluble after 40 min at 95oC) spots that were significantly more abundant in S. pectinata or missing in S. alterniflora. The association between the presence of those proteins and desiccation tolerance was further confirmed by the evidence that these proteins were still present in the desiccation tolerant, but missing in the desiccation intolerant, S. pectinata seedlings. These 83 spots were sequenced and share homologies to known proteins, e.g. late embryogenesis abundant proteins (LEAs), molecular chaperones, antioxidants, cystatin, and glyceraldehyde-3-phosphate dehydrogenase. These data suggest that LEA prevention pathways, molecular chaperone rescue pathways, ubiquitin-proteasome and autophagy degradation pathways and ROS-antioxidant systems may account for the desiccation tolerance in S. pectinata. Comparative proteomics was used to identify putative dormancy-breaking associated proteins that exhibit the same protein expression pattern during cold stratification in S. alterniflora and S. pectinata seeds. In silico gel analysis revealed that 9 individual spots were more abundant in dormant, and 7 spots were more abundant in the non-dormant state. These proteins share homologies with seed storage proteins, glycolytic enzymes, and molecular chaperones. The proteomic results suggest that degradation of storage proteins, increased cellular metabolism, and increased activities of molecular chaperones during cold stratification may be associated with dormancy release in S. alterniflora and S. pectinata. Mortality curves (seed viability versus water content) of Spartina alterniflora at different drying temperatures (4 C, 14 C and 24 C) suggest that the drying rates are temperature-dependent, but the critical water content is independent of the drying temperature in S. alterniflora.