Dehydration stress-induced oscillations in LEA protein transcripts involves abscisic acid in the moss, Physcomitrella patens

Physcomitrella patens is a bryophyte belonging to early diverging lineages of land plants following colonization of land in the Ordovician period. Mosses are typically found in refugial habitats and can experience rapidly fluctuating environmental conditions. The acquisition of dehydration tolerance by bryophytes is of fundamental importance as they lack water-conducting tissues and are generally one cell layer thick. Here, we show that dehydration induced oscillations in the steady-state transcript abundances of two group 3 late embryogenesis abundant (LEA) protein genes in P.patens protonemata, and that the amplitudes of these oscillations are reflective of the severity of dehydration stress. Dehydration stress also induced elevations in the concentrations of abscisic acid (ABA), and ABA alone can also induce dosage-dependent oscillatory increases in the steady-state abundance of LEA protein transcripts. Additionally, removal of ABA resulted in rapid attenuation of these oscillatory increases. Our data demonstrate that dehydration stress-regulated expression of LEA protein genes is temporally dynamic and highlight the importance of oscillations as a robust mechanism for optimal responses. Our results suggest that dehydration stress-induced oscillations in the steady-state abundance of LEA protein transcripts may constitute an important cellular strategy for adaptation to life in a constantly changing environment.