Desiccation tolerance in Physcomitrella patens: Rate of dehydration and the involvement of endogenous abscisic acid (ABA)

Authors: XIAO, LIHONG - Zhejiang A & F University; YOBI, ABOU - University Of Missouri; KOSTER, KAREN - University Of South Dakota; HE, YIKUN - Beijing Normal University; Oliver, Melvin

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2017
Publication Date: 11/6/2017
Publication URL: http://handle.nal.usda.gov/10113/5883831
Citation: Xiao, L., Yobi, A., Koster, K., He, Y., Oliver, M.J. 2017. Desiccation tolerance in Physcomitrella patens: Rate of dehydration and the involvement of endogenous abscisic acid (ABA). Plant Cell and Environment. 41:275-284. https://doi.org/10.1111/pce.13096.
DOI: https://doi.org/10.1111/pce.13096

Interpretive Summary: Understanding how plants cope with cellular loss of water is critical for developing new approaches to improving the drought tolerance of our major crops. Such studies are often difficult in the complex crop plants and so we often use simpler plant models to investigate how plant cells behave when water is lost. One such model is the moss Physcomitrella and in this study we have investigated how the rate of water loss from the cells determine if the plant can acquire tolerance to dehydration and to what extent the plant hormone, abscisic acid (ABA), can influence that acquisition. WE determined that if the plant is dried very slowly over several days it can actually tolerate complete drying and that ABA, although important in the tolerance of dehydration it does not trigger the acquisition of that tolerance. We also discovered that some of the genes involved in the tolerance mechanism are activated by a signaling pathway that is independent of ABA. This information will allow researchers to uncover new genetic mechanisms that induce drought tolerance and ultimately to develop new strategies for crop improvement.

Technical Abstract: The moss Physcomitrella patens, a model system for basal land plants, tolerates several abiotic stresses, including dehydration. We previously reported that Physcomitrella patens survives equilibrium dehydration to -13 MPa in a closed system at 90% RH. Tolerance of desiccation to water potentials below -100 MPa was only achieved by pre-treatment with exogenous ABA. We report here that gametophores, but not protonemata, can survive desiccation below -100 MPa after a gradual drying regime in an open system, without exogenous ABA. In contrast, faster equilibrium drying at 90% RH for 3-5 d did not induce desiccation tolerance in either tissue. Endogenous ABA accumulated in protonemata and gametophores under both drying regimes, so did not correlate directly with desiccation tolerance. Gametophores of a Ppabi3a/b/c TKO transgenic line also survived the gradual dehydration regime, despite impaired ABA signaling. Our results suggest that the initial drying rate, and not the amount of endogenous ABA, may be critical in the acquisition of desiccation tolerance. Results from this work will provide insight into ongoing studies to uncover the role of ABA in the dehydration response and the underlying mechanisms of desiccation tolerance in this bryophyte.