Planta DOI 10.1007/s00425-013-2000-3

Original Article

Photoheterotrophic growth of patens

Terry M. Bricker · Adam J. Bell · Lan Tran · Laurie K. Frankel · Steven M. Theg

Received: 1 October 2013 / Accepted: 8 November 2013 © Springer-Verlag Berlin Heidelberg 2013

Abstract Physcomitrella patens is a model bryophyte rep- non-vascular land , the earliest representatives of resenting an early land plant in the green plant lineage. This which were present at least 350–400 million years ago organism possesses many advantages as a . (Hueber 1961). The predominant life cycle stage of these Its has been sequenced, its predominant life cycle organisms is the haploid . The P. patens stage is the haploid gametophyte, it is readily transform- genome has been sequenced (Rensing et al. 2008), the able and it can integrate transformed DNA into its genome organism is transformable and can integrate exogenous by . One limitation for the use of DNA into its genome via homologous recombination P. patens in photosynthesis research is its reported inability (Schaefer and Zrÿd 1997). The ability to specifically target to grow photoheterotrophically, in the presence of sucrose genes for knockout and replacement has proved a very use- and the Photosystem II inhibitor 3-(3,4-dichlorophenyl)- ful characteristic of this organism. Recently, P. patens has 1,1-dimethylurea, which prevents linear photosynthetic been used in an increasing number of studies examining electron transport. In this communication we describe the plant , physiology and metabolism (Cove 2005; facile isolation of a P. patens strain which can grow pho- Cove et al. 2006). toheterotrophically. Additionally, we have examined a One limitation on the use of P. patens in the field of number of photosynthetic parameters for this strain grown photosynthesis is its reported inability to grow hetero- under photoautotrophic, mixotrophic (in the presence trophically (Thornton et al. 2005), i.e. in the absence of of sucrose) and photoheterotrophic conditions, as well as linear chain photosynthetic electron transport when sup- the 3-(3,4-dichlorophenyl)-1,1-dimethylurea-inhibited state. plied with a carbon source. These authors observed no The ability to grow P. patens photoheterotrophically should growth of P. patens when gametophytic explants were significantly facilitate its use in photosynthetic studies. transferred to media containing 3-(3,4-dichlorophenyl)- 1,1-dimethylurea (DCMU) and 0.5 % glucose. They also tested a number of other carbon sources, none of which Introduction could apparently support heterotrophic growth. The two organisms which have proved, arguably, among the most The Physcomitrella patens is an important devel- useful for photosynthesis research, are the cyanobacterium oping model organism. As a bryophyte, it represents a Synechocystis sp. PCC 6803 (henceforth Synechocystis 6803) and Chlamydomonas reinhardtii (henceforth Chla- mydomonas); both can utilize exogenous carbon sources * T. M. Bricker ( ) · A. J. Bell · L. K. Frankel to support growth in the absence of linear chain electron Division of Biochemistry and Molecular Biology, Department of Biological Sciences, Louisiana State University, transport. Synechocystis can be cultured photohetero- Baton Rouge, LA 70803, USA trophically in the presence of the Photosystem II (PS II) e-mail: [email protected] herbicide DCMU when supplied with glucose (Williams 1988). This has allowed the isolation of numerous PS II L. Tran · S. M. Theg Department of Plant Biology, University of California, (Williams 1988; Verma