Glycine betaine accumulation in Avicennia germinans propagules and seedlings as a function of abiotic stress

Abstract

The black mangrove (Avicennia germinans) is native to the subtropical coasts of Florida and can tolerate moderate to high salinity environments. Propagules, germinated seeds that remain attached to the maternal plants until mature, are dispersed in shallow waters and transported through currents until washing ashore, and establishing roots on an appropriate substrate to initiate growth. Recently, the poleward expansion of A. germinans has been observed. The literature and findings in our laboratory suggest that A. germinans gains its salt and temperature tolerance in part by the modified amino acid, glycine betaine (GB). We sought to investigate the expression of GB in A. germinans as a function of abiotic stressors: high saline and low temperatures. The role of endogenous GB accumulation as a function of substrate condition and temperature was investigated in propagules. The accumulation of exogenous GB was measured in seedlings exposed to various saline and temperature environments. Propagules exposed to colder temperatures accumulated more GB (100–200 ug/umol) than moderate temperatures (50 ug/umol). Propagules exposed to 18 ppt saline accumulated more GB than those exposed to 36 ppt at 0°C. Propagules exposed to saline environments accumulated more GB at 0°C compared to sand and air samples. Significantly more propagules treated at 36 ppt developed into seedlings and demonstrated faster growth rates. Additionally, an exogenous application of 10 μM GB improved seedling survival after exposure to −2°C and high saline stress (60 ppt and 100 ppt). Preliminary findings demonstrate that APX and SOD enzymes are both present in the leaf samples after these stressors. These results further characterize the role GB contributes to the ability of A. germinans to acclimate following environmental stressors. Propagules express endogenous GB in response to abiotic stress, while exogenous application of GB may confer additional protection from continued stress. Subsequent investigations will further elucidate the roles APX and SOD may influence in the GB mechanism. The significance of these findings further characterize the mechanisms by which A. germinans survive high saline environments and colder temperatures.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.