Choline monooxygenase transcript expression triggers glycine betaine accumulation in Suaeda maritima when subjected to a salt concentration optimal for its growth

Abstract

Suaeda maritima(L.) Dumort, an annual halophyte known to be a salt-accumulator is also known for the accumulation of the osmolyte, glycine betaine (GB). This study is an attempt to understand the growth and GB accumulation under optimal concentration of 200 mM NaCl in S. maritima. Salt treatment with 200 mM NaCl showed a significant increase in shoot growth after two weeks. The shoots appeared succulent and turgid after two weeks of salt treatment compared to that of the control which appeared slender and wilted. The treated seedlings also exhibited a significant increase in GB content after two weeks of salt treatment. In order to determine the molecular basis of GB accumulation, qRT PCR of three key genes involved in the pathway, choline monooxygenase, betaine aldehyde dehydrogenase and phospho-ethanolamine N-methyl transferase was performed. Transcript level expression of the three genes revealed a high up-regulation of choline monooxygeanse transcripts when compared to that of the other two transcripts at two days of salt treatment. The results indicate that S. maritima requires salt for its growth and is a natural accumulator of GB. Although all the three genes were salt inducible, the high up-regulation of choline monooxygenase greatly contributes to the accumulation of GB under optimal growth as well as NaCl concentration.